Add simple runtime benchmarks

For now we add just two binaries, one with assertions taking the fast path, one with assertions taking the slow path, and the ability to run 1 of `REQUIRE(true)`, `REQUIRE_NOTHROW`, `REQUIRE_THROWS` in a loop. I also split off a CMake preset which enables more tests than the basic `simple-tests` preset, but does not enable the most expensive tests which force recompilation of Catch2 multiple times.
Make message push/pop static
2025-09-23 21:15:39 +02:00 · 2025-09-23 17:17:33 +02:00 · 2025-09-23 11:46:26 +02:00 · 2025-09-22 15:36:46 +02:00 · 2025-09-22 14:02:45 +02:00
209 changed files with 4981 additions and 1454 deletions
--- a/.clang-format
+++ b/.clang-format
@@ -1,6 +1,6 @@
 ---
 Language: Cpp
-Standard: c++17
+Standard: c++14

 # Note that we cannot use IncludeIsMainRegex functionality, because it
 # does not support includes in angle brackets (<>)
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -28,12 +28,13 @@ Checks: >-
  -modernize-concat-nested-namespaces,
  -modernize-use-nodiscard,
  -modernize-use-default-member-init,
+  -modernize-type-traits,# we need to support C++14,
  -modernize-deprecated-headers,
  ,# There's a lot of these and most of them are probably not useful,
  -modernize-pass-by-value,

  performance-*,
-  -performance-enum-size,
+  performance-enum-size,

  portability-*,

--- a/.github/workflows/linux-meson-builds.yml
+++ b/.github/workflows/linux-meson-builds.yml
@@ -4,7 +4,7 @@ on: [push, pull_request]

 jobs:
  build:
-    name: meson ${{matrix.cxx}}, ${{matrix.build_type}}
+    name: meson ${{matrix.cxx}}, C++${{matrix.std}}, ${{matrix.build_type}}
    runs-on: ubuntu-22.04
    strategy:
      fail-fast: false
@@ -13,6 +13,7 @@ jobs:
          - g++-11
          - clang++-11
        build_type: [debug, release]
+        std: [14, 17]
        include:
          - cxx: clang++-11
            other_pkgs: clang-11
@@ -28,7 +29,7 @@ jobs:
    - name: Configure
      env:
        CXX: ${{matrix.cxx}}
-        CXXFLAGS: -std=c++17 ${{matrix.cxxflags}}
+        CXXFLAGS: -std=c++${{matrix.std}} ${{matrix.cxxflags}}
      # Note: $GITHUB_WORKSPACE is distinct from ${{runner.workspace}}.
      #       This is important
      run: |
--- a/.github/workflows/linux-other-builds.yml
+++ b/.github/workflows/linux-other-builds.yml
@@ -7,7 +7,7 @@ on: [push, pull_request]

 jobs:
  build:
-    name: ${{matrix.build_description}}, ${{matrix.cxx}}, ${{matrix.build_type}}
+    name: ${{matrix.build_description}}, ${{matrix.cxx}}, C++${{matrix.std}} ${{matrix.build_type}}
    runs-on: ubuntu-22.04
    strategy:
      fail-fast: false
@@ -20,6 +20,7 @@ jobs:
          - cxx: clang++-14
            build_description: Surrogates build
            build_type: Debug
+            std: 14
            other_pkgs: clang-14
            cmake_configurations: -DCATCH_BUILD_SURROGATES=ON

@@ -27,11 +28,13 @@ jobs:
          - cxx: g++-11
            build_description: Extras + Examples
            build_type: Debug
+            std: 14
            other_pkgs: g++-11
            cmake_configurations: -DCATCH_BUILD_EXTRA_TESTS=ON -DCATCH_BUILD_EXAMPLES=ON -DCATCH_ENABLE_CMAKE_HELPER_TESTS=ON
          - cxx: g++-11
            build_description: Extras + Examples
            build_type: Release
+            std: 14
            other_pkgs: g++-11
            cmake_configurations: -DCATCH_BUILD_EXTRA_TESTS=ON -DCATCH_BUILD_EXAMPLES=ON -DCATCH_ENABLE_CMAKE_HELPER_TESTS=ON

@@ -39,18 +42,29 @@ jobs:
          - cxx: clang++-14
            build_description: Extras + Examples
            build_type: Debug
+            std: 17
            other_pkgs: clang-14
            cmake_configurations: -DCATCH_BUILD_EXTRA_TESTS=ON -DCATCH_BUILD_EXAMPLES=ON -DCATCH_ENABLE_CMAKE_HELPER_TESTS=ON
          - cxx: clang++-14
            build_description: Extras + Examples
            build_type: Release
+            std: 17
            other_pkgs: clang-14
            cmake_configurations: -DCATCH_BUILD_EXTRA_TESTS=ON -DCATCH_BUILD_EXAMPLES=ON -DCATCH_ENABLE_CMAKE_HELPER_TESTS=ON

+          # Configure tests with Clang-14
+          - cxx: clang++-14
+            build_description: CMake configuration tests
+            build_type: Debug
+            std: 14
+            other_pkgs: clang-14
+            cmake_configurations: -DCATCH_ENABLE_CONFIGURE_TESTS=ON
+
          # Valgrind test Clang-14
          # - cxx: clang++-14
          #   build_description: Valgrind tests
          #   build_type: Debug
+          #   std: 14
          #   other_pkgs: clang-14 valgrind
          #   cmake_configurations: -DMEMORYCHECK_COMMAND=`which valgrind` -DMEMORYCHECK_COMMAND_OPTIONS="-q --track-origins=yes --leak-check=full --num-callers=50 --show-leak-kinds=definite --error-exitcode=1"
          #   other_ctest_args: -T memcheck -LE uses-python
@@ -69,6 +83,7 @@ jobs:
        cmake --preset basic-tests -GNinja \
              -DCMAKE_BUILD_TYPE=${{matrix.build_type}} \
              -DCMAKE_CXX_COMPILER=${{matrix.cxx}} \
+              -DCMAKE_CXX_STANDARD=${{matrix.std}} \
              ${{matrix.cmake_configurations}}

    - name: Build
@@ -101,6 +116,7 @@ jobs:
              -DCMAKE_CXX_COMPILER_LAUNCHER=/usr/bin/true \
              -DCMAKE_CXX_COMPILER=clang++-15 \
              -DCMAKE_CXX_LINK_EXECUTABLE=/usr/bin/true \
+              -DCMAKE_CXX_STANDARD=17 \
              -DCMAKE_RANLIB=/usr/bin/true \
              -DCATCH_BUILD_EXAMPLES=ON \
              -DCATCH_ENABLE_CMAKE_HELPER_TESTS=ON
--- a/.github/workflows/linux-simple-builds.yml
+++ b/.github/workflows/linux-simple-builds.yml
@@ -14,6 +14,7 @@ jobs:
          - g++-10
          - g++-11
          - g++-12
+          - clang++-6.0
          - clang++-7
          - clang++-8
          - clang++-9
@@ -23,7 +24,7 @@ jobs:
          - clang++-13
          - clang++-14
        build_type: [Debug, Release]
-        std: [17]
+        std: [14]
        include:
          - cxx: g++-9
            other_pkgs: g++-9
@@ -33,6 +34,8 @@ jobs:
            other_pkgs: g++-11
          - cxx: g++-12
            other_pkgs: g++-12
+          - cxx: clang++-6.0
+            other_pkgs: clang-6.0
          - cxx: clang++-7
            other_pkgs: clang-7
          - cxx: clang++-8
@@ -49,6 +52,15 @@ jobs:
            other_pkgs: clang-13
          - cxx: clang++-14
            other_pkgs: clang-14
+          # Clang 14 + C++17
+          - cxx: clang++-14
+            build_type: Debug
+            std: 17
+            other_pkgs: clang-14
+          - cxx: clang++-14
+            build_type: Release
+            std: 17
+            other_pkgs: clang-14
          - cxx: clang++-14
            build_type: Debug
            std: 20
--- a/.github/workflows/mac-builds.yml
+++ b/.github/workflows/mac-builds.yml
@@ -12,6 +12,7 @@ jobs:
      matrix:
        image: [macos-13, macos-14, macos-15]
        build_type: [Debug, Release]
+        std: [14, 17]

    steps:
    - uses: actions/checkout@v4
@@ -20,6 +21,7 @@ jobs:
      run: |
        cmake --preset basic-tests -GNinja \
              -DCMAKE_BUILD_TYPE=${{matrix.build_type}} \
+              -DCMAKE_CXX_STANDARD=${{matrix.std}} \
              -DCATCH_BUILD_EXAMPLES=ON \
              -DCATCH_BUILD_EXTRA_TESTS=ON

--- a/.github/workflows/windows-simple-builds.yml
+++ b/.github/workflows/windows-simple-builds.yml
@@ -4,7 +4,7 @@ on: [push, pull_request]

 jobs:
  build:
-    name: ${{matrix.os}}, ${{matrix.build_type}}, ${{matrix.platform}}
+    name: ${{matrix.os}}, ${{matrix.std}}, ${{matrix.build_type}}, ${{matrix.platform}}
    runs-on: ${{matrix.os}}
    strategy:
      fail-fast: false
@@ -12,6 +12,7 @@ jobs:
        os: [windows-2022, windows-2025]
        platform: [Win32, x64]
        build_type: [Debug, Release]
+        std: [14, 17]
    steps:
      - uses: actions/checkout@v4

@@ -19,6 +20,7 @@ jobs:
        run: |
          cmake --preset all-tests `
                -A ${{matrix.platform}} `
+                -DCMAKE_CXX_STANDARD=${{matrix.std}} `

      - name: Build tests
        run: cmake --build build --config ${{matrix.build_type}} --parallel %NUMBER_OF_PROCESSORS%
--- a/BUILD.bazel
+++ b/BUILD.bazel
@@ -27,6 +27,11 @@ expand_template(
        "#cmakedefine CATCH_CONFIG_COLOUR_WIN32": "",
        "#cmakedefine CATCH_CONFIG_COUNTER": "",
        "#cmakedefine CATCH_CONFIG_CPP11_TO_STRING": "",
+        "#cmakedefine CATCH_CONFIG_CPP17_BYTE": "",
+        "#cmakedefine CATCH_CONFIG_CPP17_OPTIONAL": "",
+        "#cmakedefine CATCH_CONFIG_CPP17_STRING_VIEW": "",
+        "#cmakedefine CATCH_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS": "",
+        "#cmakedefine CATCH_CONFIG_CPP17_VARIANT": "",
        "#cmakedefine CATCH_CONFIG_DEPRECATION_ANNOTATIONS": "",
        "#cmakedefine CATCH_CONFIG_DISABLE_EXCEPTIONS_CUSTOM_HANDLER": "",
        "#cmakedefine CATCH_CONFIG_DISABLE_EXCEPTIONS": "",
@@ -46,6 +51,11 @@ expand_template(
        "#cmakedefine CATCH_CONFIG_NO_COLOUR_WIN32": "",
        "#cmakedefine CATCH_CONFIG_NO_COUNTER": "",
        "#cmakedefine CATCH_CONFIG_NO_CPP11_TO_STRING": "",
+        "#cmakedefine CATCH_CONFIG_NO_CPP17_BYTE": "",
+        "#cmakedefine CATCH_CONFIG_NO_CPP17_OPTIONAL": "",
+        "#cmakedefine CATCH_CONFIG_NO_CPP17_STRING_VIEW": "",
+        "#cmakedefine CATCH_CONFIG_NO_CPP17_UNCAUGHT_EXCEPTIONS": "",
+        "#cmakedefine CATCH_CONFIG_NO_CPP17_VARIANT": "",
        "#cmakedefine CATCH_CONFIG_NO_DEPRECATION_ANNOTATIONS": "",
        "#cmakedefine CATCH_CONFIG_NO_GETENV": "",
        "#cmakedefine CATCH_CONFIG_NO_GLOBAL_NEXTAFTER": "",
--- a/CMake/CatchConfigOptions.cmake
+++ b/CMake/CatchConfigOptions.cmake
@@ -31,6 +31,11 @@ set(_OverridableOptions
  "COLOUR_WIN32"
  "COUNTER"
  "CPP11_TO_STRING"
+  "CPP17_BYTE"
+  "CPP17_OPTIONAL"
+  "CPP17_STRING_VIEW"
+  "CPP17_UNCAUGHT_EXCEPTIONS"
+  "CPP17_VARIANT"
  "GLOBAL_NEXTAFTER"
  "POSIX_SIGNALS"
  "USE_ASYNC"
--- a/CMake/catch2-with-main.pc.in
+++ b/CMake/catch2-with-main.pc.in
@@ -3,7 +3,7 @@ libdir=${prefix}/@lib_dir@
 pkg_version=@Catch2_VERSION@

 Name: Catch2 with main function
-Description: A modern, C++-native test framework for C++17 and above (links in default main)
+Description: A modern, C++-native test framework for C++14 and above (links in default main)
 URL: https://github.com/catchorg/Catch2
 Version: ${pkg_version}
 Requires: catch2 = ${pkg_version}
--- a/CMake/catch2.pc.in
+++ b/CMake/catch2.pc.in
@@ -4,7 +4,7 @@ includedir=${prefix}/@include_dir@
 libdir=${prefix}/@lib_dir@

 Name: Catch2
-Description: A modern, C++-native, test framework for C++17 and above
+Description: A modern, C++-native, test framework for C++14 and above
 URL: https://github.com/catchorg/Catch2
 Version: @Catch2_VERSION@
 Cflags: -I${includedir}
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -20,6 +20,7 @@ cmake_dependent_option(CATCH_BUILD_TESTING "Build the SelfTest project" ON "CATC
 cmake_dependent_option(CATCH_BUILD_EXAMPLES "Build code examples" OFF "CATCH_DEVELOPMENT_BUILD" OFF)
 cmake_dependent_option(CATCH_BUILD_EXTRA_TESTS "Build extra tests" OFF "CATCH_DEVELOPMENT_BUILD" OFF)
 cmake_dependent_option(CATCH_BUILD_FUZZERS "Build fuzzers" OFF "CATCH_DEVELOPMENT_BUILD" OFF)
+cmake_dependent_option(CATCH_BUILD_BENCHMARKS "Build the benchmarks" OFF "CATCH_DEVELOPMENT_BUILD" OFF)
 cmake_dependent_option(CATCH_ENABLE_COVERAGE "Generate coverage for codecov.io" OFF "CATCH_DEVELOPMENT_BUILD" OFF)
 cmake_dependent_option(CATCH_ENABLE_WERROR "Enables Werror during build" ON "CATCH_DEVELOPMENT_BUILD" OFF)
 cmake_dependent_option(CATCH_BUILD_SURROGATES "Enable generating and building surrogate TUs for the main headers" OFF "CATCH_DEVELOPMENT_BUILD" OFF)
@@ -77,6 +78,11 @@ set(SELF_TEST_DIR ${CATCH_DIR}/tests/SelfTest)
 # We need to bring-in the variables defined there to this scope
 add_subdirectory(src)

+if (CATCH_BUILD_BENCHMARKS)
+  set(CMAKE_FOLDER "benchmarks")
+  add_subdirectory(benchmarks)
+endif()
+
 # Build tests only if requested
 if(BUILD_TESTING AND CATCH_BUILD_TESTING AND NOT_SUBPROJECT)
  find_package(Python3 REQUIRED COMPONENTS Interpreter)
--- a/CMakePresets.json
+++ b/CMakePresets.json
@@ -11,19 +11,27 @@
                "CMAKE_CXX_EXTENSIONS": "OFF",
                "CMAKE_CXX_STANDARD_REQUIRED": "ON",
                "CMAKE_EXPORT_COMPILE_COMMANDS": "ON",
-                "CATCH_DEVELOPMENT_BUILD": "ON",
-                "CATCH_ENABLE_REPRODUCIBLE_BUILD": "OFF"
+                "CATCH_DEVELOPMENT_BUILD": "ON"
            }
        },
        {
-            "name": "all-tests",
+            "name": "most-tests",
            "inherits": "basic-tests",
            "displayName": "Full development build",
-            "description": "Enables development build with examples and ALL tests",
+            "description": "Enables development build with extended set of tests (still relatively cheap to build)",
            "cacheVariables": {
                "CATCH_BUILD_EXAMPLES": "ON",
                "CATCH_BUILD_EXTRA_TESTS": "ON",
                "CATCH_BUILD_SURROGATES": "ON",
+                "CATCH_BUILD_BENCHMARKS": "ON"
+            }
+        },
+        {
+            "name": "all-tests",
+            "inherits": "most-tests",
+            "displayName": "Full development build",
+            "description": "Enables development build with examples and ALL tests",
+            "cacheVariables": {
                "CATCH_ENABLE_CONFIGURE_TESTS": "ON",
                "CATCH_ENABLE_CMAKE_HELPER_TESTS": "ON"
            }
--- a/benchmarks/CMakeLists.txt
+++ b/benchmarks/CMakeLists.txt
@@ -0,0 +1,16 @@
+include(CatchMiscFunctions)
+
+add_executable(AssertionsFastPath
+  runtime_assertion_benches.cpp
+)
+
+add_executable(AssertionsSlowPath
+  runtime_assertion_benches.cpp
+  assertion_listener.cpp
+)
+
+target_link_libraries(AssertionsFastPath PRIVATE Catch2::Catch2WithMain)
+target_link_libraries(AssertionsSlowPath PRIVATE Catch2::Catch2WithMain)
+
+list(APPEND CATCH_TEST_TARGETS AssertionsFastPath AssertionsSlowPath)
+set(CATCH_TEST_TARGETS ${CATCH_TEST_TARGETS} PARENT_SCOPE)
--- a/benchmarks/assertion_listener.cpp
+++ b/benchmarks/assertion_listener.cpp
@@ -0,0 +1,28 @@
+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+
+#include <catch2/reporters/catch_reporter_event_listener.hpp>
+#include <catch2/reporters/catch_reporter_registrars.hpp>
+
+/**
+ * Event listener that listens to all assertions, forcing assertion slow path
+ */
+class AssertionSlowPathListener : public Catch::EventListenerBase {
+public:
+    static std::string getDescription() {
+        return "Validates ordering of Catch2's listener events";
+    }
+
+    AssertionSlowPathListener(Catch::IConfig const* config) :
+        EventListenerBase(config) {
+        m_preferences.shouldReportAllAssertions = true;
+        m_preferences.shouldReportAllAssertionStarts = true;
+    }
+};
+
+CATCH_REGISTER_LISTENER( AssertionSlowPathListener )
--- a/benchmarks/runtime_assertion_benches.cpp
+++ b/benchmarks/runtime_assertion_benches.cpp
@@ -0,0 +1,27 @@
+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+
+#include <catch2/catch_test_macros.hpp>
+
+TEST_CASE("Simple REQUIRE - 10M") {
+    for (size_t i = 0; i < 10'000'000; ++i) {
+        REQUIRE(true);
+    }
+}
+
+TEST_CASE("Simple NOTHROW - 10M") {
+    for (size_t i = 0; i < 10'000'000; ++i) {
+        REQUIRE_NOTHROW([](){}());
+    }
+}
+
+TEST_CASE("Simple THROWS - 10M") {
+    for (size_t i = 0; i < 10'000'000; ++i) {
+        REQUIRE_THROWS([]() { throw 1; }());
+    }
+}
--- a/docs/ci-and-misc.md
+++ b/docs/ci-and-misc.md
@@ -66,11 +66,14 @@ test execution. Specifically it understands
 * JUnit output path via `XML_OUTPUT_FILE`
 * Test filtering via `TESTBRIDGE_TEST_ONLY`
 * Test sharding via `TEST_SHARD_INDEX`, `TEST_TOTAL_SHARDS`, and `TEST_SHARD_STATUS_FILE`
+ * Creating a file to signal premature test exit via `TEST_PREMATURE_EXIT_FILE`

 > Support for `XML_OUTPUT_FILE` was [introduced](https://github.com/catchorg/Catch2/pull/2399) in Catch2 3.0.1

 > Support for `TESTBRIDGE_TEST_ONLY` and sharding was introduced in Catch2 3.2.0

+> Support for `TEST_PREMATURE_EXIT_FILE` was introduced in Catch2 X.Y.Z
+
 This integration is enabled via either a [compile time configuration
 option](configuration.md#bazel-support), or via `BAZEL_TEST` environment
 variable set to "1".
--- a/docs/command-line.md
+++ b/docs/command-line.md
@@ -32,6 +32,7 @@
 [Test Sharding](#test-sharding)<br>
 [Allow running the binary without tests](#allow-running-the-binary-without-tests)<br>
 [Output verbosity](#output-verbosity)<br>
+[Create file to guard against silent early termination](#create-file-to-guard-against-silent-early-termination)<br>

 Catch works quite nicely without any command line options at all - but for those times when you want greater control the following options are available.
 Click one of the following links to take you straight to that option - or scroll on to browse the available options.
@@ -649,6 +650,21 @@ ignored.
 Verbosity defaults to _normal_.


+## Create file to guard against silent early termination
+<pre>--premature-exit-guard-file &lt;path&gt;</pre>
+
+> Introduced in Catch2 X.Y.Z
+
+Tells Catch2 to create an empty file at specified path before the tests
+start, and delete it after the tests finish. If the file is present after
+the process stops, it can be assumed that the testing binary exited
+prematurely, e.g. due to the OOM killer.
+
+All directories in the path must already exist. If this option is used
+and Catch2 cannot create the file (e.g. the location is not writable),
+the test run will fail.
+
+
 ---

 [Home](Readme.md#top)
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -10,6 +10,7 @@
 [Default reporter](#default-reporter)<br>
 [Bazel support](#bazel-support)<br>
 [C++11 toggles](#c11-toggles)<br>
+[C++17 toggles](#c17-toggles)<br>
 [Other toggles](#other-toggles)<br>
 [Enabling stringification](#enabling-stringification)<br>
 [Disabling exceptions](#disabling-exceptions)<br>
@@ -127,6 +128,23 @@ Catch's selection, by defining either `CATCH_CONFIG_CPP11_TO_STRING` or
 `CATCH_CONFIG_NO_CPP11_TO_STRING`.


+## C++17 toggles
+
+    CATCH_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS  // Override std::uncaught_exceptions (instead of std::uncaught_exception) support detection
+    CATCH_CONFIG_CPP17_STRING_VIEW          // Override std::string_view support detection (Catch provides a StringMaker specialization by default)
+    CATCH_CONFIG_CPP17_VARIANT              // Override std::variant support detection (checked by CATCH_CONFIG_ENABLE_VARIANT_STRINGMAKER)
+    CATCH_CONFIG_CPP17_OPTIONAL             // Override std::optional support detection (checked by CATCH_CONFIG_ENABLE_OPTIONAL_STRINGMAKER)
+    CATCH_CONFIG_CPP17_BYTE                 // Override std::byte support detection (Catch provides a StringMaker specialization by default)
+
+> `CATCH_CONFIG_CPP17_STRING_VIEW` was [introduced](https://github.com/catchorg/Catch2/issues/1376) in Catch2 2.4.1.
+
+Catch contains basic compiler/standard detection and attempts to use
+some C++17 features whenever appropriate. This automatic detection
+can be manually overridden in both directions, that is, a feature
+can be enabled by defining the macro in the table above, and disabled
+by using `_NO_` in the macro, e.g. `CATCH_CONFIG_NO_CPP17_UNCAUGHT_EXCEPTIONS`.
+
+
 ## Other toggles

    CATCH_CONFIG_COUNTER                    // Use __COUNTER__ to generate unique names for test cases
@@ -203,8 +221,8 @@ By default, Catch does not stringify some types from the standard library. This

    CATCH_CONFIG_ENABLE_PAIR_STRINGMAKER     // Provide StringMaker specialization for std::pair
    CATCH_CONFIG_ENABLE_TUPLE_STRINGMAKER    // Provide StringMaker specialization for std::tuple
-    CATCH_CONFIG_ENABLE_VARIANT_STRINGMAKER  // Provide StringMaker specialization for std::variant, std::monostate
-    CATCH_CONFIG_ENABLE_OPTIONAL_STRINGMAKER // Provide StringMaker specialization for std::optional
+    CATCH_CONFIG_ENABLE_VARIANT_STRINGMAKER  // Provide StringMaker specialization for std::variant, std::monostate (on C++17)
+    CATCH_CONFIG_ENABLE_OPTIONAL_STRINGMAKER // Provide StringMaker specialization for std::optional (on C++17)
    CATCH_CONFIG_ENABLE_ALL_STRINGMAKERS     // Defines all of the above

 > `CATCH_CONFIG_ENABLE_VARIANT_STRINGMAKER` was [introduced](https://github.com/catchorg/Catch2/issues/1380) in Catch2 2.4.1.
--- a/docs/contributing.md
+++ b/docs/contributing.md
@@ -211,10 +211,16 @@ and so on.

 ### C++ standard version

-Catch2 currently targets C++17 as the minimum supported C++ version.
+Catch2 currently targets C++14 as the minimum supported C++ version.
 Features from higher language versions should be used only sparingly,
 when the benefits from using them outweigh the maintenance overhead.

+Example of good use of polyfilling features is our use of `conjunction`,
+where if available we use `std::conjunction` and otherwise provide our
+own implementation. The reason it is good is that the surface area for
+maintenance is quite small, and `std::conjunction` can directly use
+compiler built-ins, thus providing significant compilation benefits.
+
 Example of bad use of polyfilling features would be to keep around two
 sets of metaprogramming in the stringification implementation, once
 using C++14 compliant TMP and once using C++17's `if constexpr`. While
--- a/docs/other-macros.md
+++ b/docs/other-macros.md
@@ -72,8 +72,8 @@ including the Catch2 header.
 Example:
 ```cpp
 TEST_CASE("STATIC_REQUIRE showcase", "[traits]") {
-    STATIC_REQUIRE( std::is_void_v<void> );
-    STATIC_REQUIRE_FALSE( std::is_void_v<int> );
+    STATIC_REQUIRE( std::is_void<void>::value );
+    STATIC_REQUIRE_FALSE( std::is_void<int>::value );
 }
 ```

@@ -86,8 +86,8 @@ becomes equivalent to `CHECK` instead of `REQUIRE`.
 Example:
 ```cpp
 TEST_CASE("STATIC_CHECK showcase", "[traits]") {
-    STATIC_CHECK( std::is_void_v<void> );
-    STATIC_CHECK_FALSE( std::is_void_v<int> );
+    STATIC_CHECK( std::is_void<void>::value );
+    STATIC_CHECK_FALSE( std::is_void<int>::value );
 }
 ```

--- a/docs/reporter-events.md
+++ b/docs/reporter-events.md
@@ -109,10 +109,10 @@ and then `assertionEnded` event is emitted.
 > [Introduced](https://github.com/catchorg/Catch2/issues/1616) in Catch2 2.9.0.

 ```cpp
-void benchmarkPreparing( std::string_view name ) override;
+void benchmarkPreparing( StringRef name ) override;
 void benchmarkStarting( BenchmarkInfo const& benchmarkInfo ) override;
 void benchmarkEnded( BenchmarkStats<> const& benchmarkStats ) override;
-void benchmarkFailed( std::string_view error ) override;
+void benchmarkFailed( StringRef error ) override;
 ```

 Due to the benchmark lifecycle being bit more complicated, the benchmarking
@@ -153,9 +153,9 @@ void listTags( std::vector<TagInfo> const& tagInfos );
 ## Miscellaneous events

 ```cpp
-void reportInvalidTestSpec( std::string_view unmatchedSpec );
-void fatalErrorEncountered( std::string_view error );
-void noMatchingTestCases( std::string_view unmatchedSpec );
+void reportInvalidTestSpec( StringRef unmatchedSpec );
+void fatalErrorEncountered( StringRef error );
+void noMatchingTestCases( StringRef unmatchedSpec );
 ```

 These are one-off events that do not neatly fit into other categories.
--- a/docs/test-cases-and-sections.md
+++ b/docs/test-cases-and-sections.md
@@ -264,7 +264,7 @@ You can also have different arities in the _template-arg_ packs:
 ```cpp
 TEMPLATE_PRODUCT_TEST_CASE("Product with differing arities", "[template][product]", std::tuple, (int, (int, double), (int, double, float))) {
    TestType x;
-    REQUIRE(std::tuple_size_v<TestType> >= 1);
+    REQUIRE(std::tuple_size<TestType>::value >= 1);
 }
 ```

--- a/docs/why-catch.md
+++ b/docs/why-catch.md
@@ -15,7 +15,7 @@ So what does Catch2 bring to the party that differentiates it from these? Apart
 ## Key Features

 * Quick and easy to get started. Just download two files, add them into your project and you're away.
-* No external dependencies. As long as you can compile C++17 and have the C++ standard library available.
+* No external dependencies. As long as you can compile C++14 and have the C++ standard library available.
 * Write test cases as, self-registering, functions (or methods, if you prefer).
 * Divide test cases into sections, each of which is run in isolation (eliminates the need for fixtures).
 * Use BDD-style Given-When-Then sections as well as traditional unit test cases.
--- a/examples/010-TestCase.cpp
+++ b/examples/010-TestCase.cpp
@@ -27,7 +27,7 @@ TEST_CASE( "Factorials of 1 and higher are computed (pass)", "[single-file]" ) {
 }

 // Compile & run:
-// - g++ -std=c++17 -Wall -I$(CATCH_SINGLE_INCLUDE) -o 010-TestCase 010-TestCase.cpp && 010-TestCase --success
+// - g++ -std=c++14 -Wall -I$(CATCH_SINGLE_INCLUDE) -o 010-TestCase 010-TestCase.cpp && 010-TestCase --success
 // - cl -EHsc -I%CATCH_SINGLE_INCLUDE% 010-TestCase.cpp && 010-TestCase --success

 // Expected compact output (all assertions):
--- a/examples/020-TestCase-1.cpp
+++ b/examples/020-TestCase-1.cpp
@@ -18,8 +18,8 @@ TEST_CASE( "1: All test cases reside in other .cpp files (empty)", "[multi-file:
 // Here just to show there are two source files via option --list-tests.

 // Compile & run:
-// - g++ -std=c++17 -Wall -I$(CATCH_SINGLE_INCLUDE) -c 020-TestCase-1.cpp
-// - g++ -std=c++17 -Wall -I$(CATCH_SINGLE_INCLUDE) -o 020-TestCase TestCase-1.o 020-TestCase-2.cpp && 020-TestCase --success
+// - g++ -std=c++14 -Wall -I$(CATCH_SINGLE_INCLUDE) -c 020-TestCase-1.cpp
+// - g++ -std=c++14 -Wall -I$(CATCH_SINGLE_INCLUDE) -o 020-TestCase TestCase-1.o 020-TestCase-2.cpp && 020-TestCase --success
 //
 // - cl -EHsc -I%CATCH_SINGLE_INCLUDE% -c 020-TestCase-1.cpp
 // - cl -EHsc -I%CATCH_SINGLE_INCLUDE% -Fe020-TestCase.exe 020-TestCase-1.obj 020-TestCase-2.cpp && 020-TestCase --success
--- a/examples/030-Asn-Require-Check.cpp
+++ b/examples/030-Asn-Require-Check.cpp
@@ -61,7 +61,7 @@ TEST_CASE( "Assert that something is false (continue after failure)", "[check-fa
 }

 // Compile & run:
-// - g++ -std=c++17 -Wall -I$(CATCH_SINGLE_INCLUDE) -o 030-Asn-Require-Check 030-Asn-Require-Check.cpp && 030-Asn-Require-Check --success
+// - g++ -std=c++14 -Wall -I$(CATCH_SINGLE_INCLUDE) -o 030-Asn-Require-Check 030-Asn-Require-Check.cpp && 030-Asn-Require-Check --success
 // - cl -EHsc -I%CATCH_SINGLE_INCLUDE% 030-Asn-Require-Check.cpp && 030-Asn-Require-Check --success

 // Expected compact output (all assertions):
--- a/examples/100-Fix-Section.cpp
+++ b/examples/100-Fix-Section.cpp
@@ -53,7 +53,7 @@ TEST_CASE( "vectors can be sized and resized", "[vector]" ) {
 }

 // Compile & run:
-// - g++ -std=c++17 -Wall -I$(CATCH_SINGLE_INCLUDE) -o 100-Fix-Section 100-Fix-Section.cpp && 100-Fix-Section --success
+// - g++ -std=c++14 -Wall -I$(CATCH_SINGLE_INCLUDE) -o 100-Fix-Section 100-Fix-Section.cpp && 100-Fix-Section --success
 // - cl -EHsc -I%CATCH_SINGLE_INCLUDE% 100-Fix-Section.cpp && 100-Fix-Section --success

 // Expected compact output (all assertions):
--- a/examples/110-Fix-ClassFixture.cpp
+++ b/examples/110-Fix-ClassFixture.cpp
@@ -60,11 +60,11 @@ TEST_CASE_METHOD( UniqueTestsFixture, "Create Employee/Normal", "[create]" ) {
 }

 // Compile & run:
-// - g++ -std=c++17 -Wall -I$(CATCH_SINGLE_INCLUDE) -o 110-Fix-ClassFixture 110-Fix-ClassFixture.cpp && 110-Fix-ClassFixture --success
+// - g++ -std=c++14 -Wall -I$(CATCH_SINGLE_INCLUDE) -o 110-Fix-ClassFixture 110-Fix-ClassFixture.cpp && 110-Fix-ClassFixture --success
 // - cl -EHsc -I%CATCH_SINGLE_INCLUDE% 110-Fix-ClassFixture.cpp && 110-Fix-ClassFixture --success
 //
 // Compile with pkg-config:
-// - g++ -std=c++17 -Wall $(pkg-config catch2-with-main --cflags)  -o 110-Fix-ClassFixture 110-Fix-ClassFixture.cpp $(pkg-config catch2-with-main --libs)
+// - g++ -std=c++14 -Wall $(pkg-config catch2-with-main --cflags)  -o 110-Fix-ClassFixture 110-Fix-ClassFixture.cpp $(pkg-config catch2-with-main --libs)

 // Expected compact output (all assertions):
 //
--- a/examples/120-Bdd-ScenarioGivenWhenThen.cpp
+++ b/examples/120-Bdd-ScenarioGivenWhenThen.cpp
@@ -56,7 +56,7 @@ SCENARIO( "vectors can be sized and resized", "[vector]" ) {
 }

 // Compile & run:
-// - g++ -std=c++17 -Wall -I$(CATCH_SINGLE_INCLUDE) -o 120-Bdd-ScenarioGivenWhenThen 120-Bdd-ScenarioGivenWhenThen.cpp && 120-Bdd-ScenarioGivenWhenThen --success
+// - g++ -std=c++14 -Wall -I$(CATCH_SINGLE_INCLUDE) -o 120-Bdd-ScenarioGivenWhenThen 120-Bdd-ScenarioGivenWhenThen.cpp && 120-Bdd-ScenarioGivenWhenThen --success
 // - cl -EHsc -I%CATCH_SINGLE_INCLUDE% 120-Bdd-ScenarioGivenWhenThen.cpp && 120-Bdd-ScenarioGivenWhenThen --success

 // Expected compact output (all assertions):
--- a/examples/210-Evt-EventListeners.cpp
+++ b/examples/210-Evt-EventListeners.cpp
@@ -131,7 +131,7 @@ void print( std::ostream& os, int const level, std::string const& title, Catch::
 }

 //    struct Tag {
-//        std::string_view original, lowerCased;
+//        StringRef original, lowerCased;
 //    };
 //
 //
@@ -221,9 +221,9 @@ void print( std::ostream& os, int const level, std::string const& title, Catch::

 // struct AssertionInfo
 // {
-//     std::string_view macroName;
+//     StringRef macroName;
 //     SourceLineInfo lineInfo;
-//     std::string_view capturedExpression;
+//     StringRef capturedExpression;
 //     ResultDisposition::Flags resultDisposition;
 // };

@@ -427,7 +427,7 @@ TEST_CASE_METHOD( Fixture, "3: Testcase with class-based fixture", "[tag-C][tag-
 }

 // Compile & run:
-// - g++ -std=c++17 -Wall -I$(CATCH_SINGLE_INCLUDE) -o 210-Evt-EventListeners 210-Evt-EventListeners.cpp && 210-Evt-EventListeners --success
+// - g++ -std=c++14 -Wall -I$(CATCH_SINGLE_INCLUDE) -o 210-Evt-EventListeners 210-Evt-EventListeners.cpp && 210-Evt-EventListeners --success
 // - cl -EHsc -I%CATCH_SINGLE_INCLUDE% 210-Evt-EventListeners.cpp && 210-Evt-EventListeners --success

 // Expected compact output (all assertions):
--- a/examples/302-Gen-Table.cpp
+++ b/examples/302-Gen-Table.cpp
@@ -22,21 +22,24 @@ struct TestSubject {


 TEST_CASE("Table allows pre-computed test inputs and outputs", "[example][generator]") {
+    using std::make_tuple;
    // do setup here as normal
    TestSubject subj;

    SECTION("This section is run for each row in the table") {
-        const auto [test_input, expected_output] =
+        std::string test_input;
+        size_t expected_output;
+        std::tie( test_input, expected_output ) =
            GENERATE( table<std::string, size_t>(
                { /* In this case one of the parameters to our test case is the
                   * expected output, but this is not required. There could be
                   * multiple expected values in the table, which can have any
                   * (fixed) number of columns.
                   */
-                  { "one", 3 },
-                  { "two", 3 },
-                  { "three", 5 },
-                  { "four", 4 } } ) );
+                  make_tuple( "one", 3 ),
+                  make_tuple( "two", 3 ),
+                  make_tuple( "three", 5 ),
+                  make_tuple( "four", 4 ) } ) );

        // run the test
        auto result = subj.GetLength(test_input);
@@ -47,4 +50,14 @@ TEST_CASE("Table allows pre-computed test inputs and outputs", "[example][genera
    }   // end section
 }

+/* Possible simplifications where less legacy toolchain support is needed:
+ *
+ * - With libstdc++6 or newer, the make_tuple() calls can be omitted
+ * (technically C++17 but does not require -std in GCC/Clang). See
+ *   https://stackoverflow.com/questions/12436586/tuple-vector-and-initializer-list
+ *
+ * - In C++17 mode std::tie() and the preceding variable declarations can be
+ * replaced by structured bindings: auto [test_input, expected] = GENERATE(
+ * table<std::string, size_t>({ ...
+ */
 // Compiling and running this file will result in 4 successful assertions
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -76,9 +76,11 @@ set(IMPL_HEADERS
  ${SOURCES_DIR}/internal/catch_config_counter.hpp
  ${SOURCES_DIR}/internal/catch_config_prefix_messages.hpp
  ${SOURCES_DIR}/internal/catch_config_static_analysis_support.hpp
+  ${SOURCES_DIR}/internal/catch_config_uncaught_exceptions.hpp
  ${SOURCES_DIR}/internal/catch_config_wchar.hpp
  ${SOURCES_DIR}/internal/catch_console_colour.hpp
  ${SOURCES_DIR}/internal/catch_console_width.hpp
+  ${SOURCES_DIR}/internal/catch_container_nonmembers.hpp
  ${SOURCES_DIR}/internal/catch_context.hpp
  ${SOURCES_DIR}/internal/catch_debug_console.hpp
  ${SOURCES_DIR}/internal/catch_debugger.hpp
@@ -97,10 +99,12 @@ set(IMPL_HEADERS
  ${SOURCES_DIR}/internal/catch_lazy_expr.hpp
  ${SOURCES_DIR}/internal/catch_leak_detector.hpp
  ${SOURCES_DIR}/internal/catch_list.hpp
+  ${SOURCES_DIR}/internal/catch_logical_traits.hpp
  ${SOURCES_DIR}/internal/catch_message_info.hpp
  ${SOURCES_DIR}/internal/catch_meta.hpp
  ${SOURCES_DIR}/internal/catch_move_and_forward.hpp
  ${SOURCES_DIR}/internal/catch_noncopyable.hpp
+  ${SOURCES_DIR}/internal/catch_optional.hpp
  ${SOURCES_DIR}/internal/catch_output_redirect.hpp
  ${SOURCES_DIR}/internal/catch_parse_numbers.hpp
  ${SOURCES_DIR}/internal/catch_platform.hpp
@@ -124,6 +128,7 @@ set(IMPL_HEADERS
  ${SOURCES_DIR}/internal/catch_stdstreams.hpp
  ${SOURCES_DIR}/internal/catch_stream_end_stop.hpp
  ${SOURCES_DIR}/internal/catch_string_manip.hpp
+  ${SOURCES_DIR}/internal/catch_stringref.hpp
  ${SOURCES_DIR}/internal/catch_tag_alias_registry.hpp
  ${SOURCES_DIR}/internal/catch_template_test_registry.hpp
  ${SOURCES_DIR}/internal/catch_test_case_info_hasher.hpp
@@ -200,6 +205,7 @@ set(IMPL_SOURCES
  ${SOURCES_DIR}/internal/catch_startup_exception_registry.cpp
  ${SOURCES_DIR}/internal/catch_stdstreams.cpp
  ${SOURCES_DIR}/internal/catch_string_manip.cpp
+  ${SOURCES_DIR}/internal/catch_stringref.cpp
  ${SOURCES_DIR}/internal/catch_tag_alias_registry.cpp
  ${SOURCES_DIR}/internal/catch_test_case_info_hasher.cpp
  ${SOURCES_DIR}/internal/catch_test_case_registry_impl.cpp
@@ -359,8 +365,8 @@ set_target_properties(Catch2 PROPERTIES
  SOVERSION ${PROJECT_VERSION}
 )

-# require C++17
-target_compile_features(Catch2 PUBLIC cxx_std_17)
+# require C++14
+target_compile_features(Catch2 PUBLIC cxx_std_14)

 configure_file(
  "${SOURCES_DIR}/catch_user_config.hpp.in"
@@ -444,7 +450,7 @@ if(CATCH_BUILD_EXAMPLES OR CATCH_BUILD_EXTRA_TESTS)
      $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
  )
  target_compile_definitions(Catch2_buildall_interface INTERFACE CATCH_CONFIG_STATIC)
-  target_compile_features(Catch2_buildall_interface INTERFACE cxx_std_17)
+  target_compile_features(Catch2_buildall_interface INTERFACE cxx_std_14)
 endif()

 list(APPEND CATCH_IMPL_TARGETS Catch2 Catch2WithMain)
--- a/src/catch2/benchmark/catch_optimizer.hpp
+++ b/src/catch2/benchmark/catch_optimizer.hpp
@@ -64,12 +64,12 @@ namespace Catch {
        }

        template <typename Fn, typename... Args>
-        inline auto invoke_deoptimized(Fn&& fn, Args&&... args) -> std::enable_if_t<!std::is_same_v<void, decltype(fn(args...))>> {
+        inline auto invoke_deoptimized(Fn&& fn, Args&&... args) -> std::enable_if_t<!std::is_same<void, decltype(fn(args...))>::value> {
            deoptimize_value(CATCH_FORWARD(fn) (CATCH_FORWARD(args)...));
        }

        template <typename Fn, typename... Args>
-        inline auto invoke_deoptimized(Fn&& fn, Args&&... args) -> std::enable_if_t<std::is_same_v<void, decltype(fn(args...))>> {
+        inline auto invoke_deoptimized(Fn&& fn, Args&&... args) -> std::enable_if_t<std::is_same<void, decltype(fn(args...))>::value> {
            CATCH_FORWARD((fn)) (CATCH_FORWARD(args)...);
        }
    } // namespace Benchmark
--- a/src/catch2/benchmark/detail/catch_analyse.cpp
+++ b/src/catch2/benchmark/detail/catch_analyse.cpp
@@ -46,7 +46,7 @@ namespace Catch {
                    std::vector<FDuration> samples2;
                    samples2.reserve(samples.size());
                    for (auto s : samples) {
-                        samples2.emplace_back( s );
+                        samples2.push_back( FDuration( s ) );
                    }

                    return {
--- a/src/catch2/benchmark/detail/catch_benchmark_function.hpp
+++ b/src/catch2/benchmark/detail/catch_benchmark_function.hpp
@@ -21,7 +21,7 @@ namespace Catch {
    namespace Benchmark {
        namespace Detail {
            template <typename T, typename U>
-            static constexpr bool is_related_v = std::is_same_v<std::decay_t<T>, std::decay_t<U>>;
+            static constexpr bool is_related_v = std::is_same<std::decay_t<T>, std::decay_t<U>>::value;

            /// We need to reinvent std::function because every piece of code that might add overhead
            /// in a measurement context needs to have consistent performance characteristics so that we
--- a/src/catch2/catch_all.hpp
+++ b/src/catch2/catch_all.hpp
@@ -57,9 +57,11 @@
 #include <catch2/internal/catch_config_counter.hpp>
 #include <catch2/internal/catch_config_prefix_messages.hpp>
 #include <catch2/internal/catch_config_static_analysis_support.hpp>
+#include <catch2/internal/catch_config_uncaught_exceptions.hpp>
 #include <catch2/internal/catch_config_wchar.hpp>
 #include <catch2/internal/catch_console_colour.hpp>
 #include <catch2/internal/catch_console_width.hpp>
+#include <catch2/internal/catch_container_nonmembers.hpp>
 #include <catch2/internal/catch_context.hpp>
 #include <catch2/internal/catch_debug_console.hpp>
 #include <catch2/internal/catch_debugger.hpp>
@@ -78,10 +80,12 @@
 #include <catch2/internal/catch_lazy_expr.hpp>
 #include <catch2/internal/catch_leak_detector.hpp>
 #include <catch2/internal/catch_list.hpp>
+#include <catch2/internal/catch_logical_traits.hpp>
 #include <catch2/internal/catch_message_info.hpp>
 #include <catch2/internal/catch_meta.hpp>
 #include <catch2/internal/catch_move_and_forward.hpp>
 #include <catch2/internal/catch_noncopyable.hpp>
+#include <catch2/internal/catch_optional.hpp>
 #include <catch2/internal/catch_output_redirect.hpp>
 #include <catch2/internal/catch_parse_numbers.hpp>
 #include <catch2/internal/catch_platform.hpp>
@@ -106,6 +110,7 @@
 #include <catch2/internal/catch_stdstreams.hpp>
 #include <catch2/internal/catch_stream_end_stop.hpp>
 #include <catch2/internal/catch_string_manip.hpp>
+#include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_tag_alias_registry.hpp>
 #include <catch2/internal/catch_template_test_registry.hpp>
 #include <catch2/internal/catch_test_case_info_hasher.hpp>
--- a/src/catch2/catch_approx.hpp
+++ b/src/catch2/catch_approx.hpp
@@ -29,7 +29,7 @@ namespace Catch {

        Approx operator-() const;

-        template <typename T, typename = std::enable_if_t<std::is_constructible_v<double, T>>>
+        template <typename T, typename = std::enable_if_t<std::is_constructible<double, T>::value>>
        Approx operator()( T const& value ) const {
            Approx approx( static_cast<double>(value) );
            approx.m_epsilon = m_epsilon;
@@ -38,67 +38,67 @@ namespace Catch {
            return approx;
        }

-        template <typename T, typename = std::enable_if_t<std::is_constructible_v<double, T>>>
+        template <typename T, typename = std::enable_if_t<std::is_constructible<double, T>::value>>
        explicit Approx( T const& value ): Approx(static_cast<double>(value))
        {}


-        template <typename T, typename = std::enable_if_t<std::is_constructible_v<double, T>>>
+        template <typename T, typename = std::enable_if_t<std::is_constructible<double, T>::value>>
        friend bool operator == ( const T& lhs, Approx const& rhs ) {
            auto lhs_v = static_cast<double>(lhs);
            return rhs.equalityComparisonImpl(lhs_v);
        }

-        template <typename T, typename = std::enable_if_t<std::is_constructible_v<double, T>>>
+        template <typename T, typename = std::enable_if_t<std::is_constructible<double, T>::value>>
        friend bool operator == ( Approx const& lhs, const T& rhs ) {
            return operator==( rhs, lhs );
        }

-        template <typename T, typename = std::enable_if_t<std::is_constructible_v<double, T>>>
+        template <typename T, typename = std::enable_if_t<std::is_constructible<double, T>::value>>
        friend bool operator != ( T const& lhs, Approx const& rhs ) {
            return !operator==( lhs, rhs );
        }

-        template <typename T, typename = std::enable_if_t<std::is_constructible_v<double, T>>>
+        template <typename T, typename = std::enable_if_t<std::is_constructible<double, T>::value>>
        friend bool operator != ( Approx const& lhs, T const& rhs ) {
            return !operator==( rhs, lhs );
        }

-        template <typename T, typename = std::enable_if_t<std::is_constructible_v<double, T>>>
+        template <typename T, typename = std::enable_if_t<std::is_constructible<double, T>::value>>
        friend bool operator <= ( T const& lhs, Approx const& rhs ) {
            return static_cast<double>(lhs) < rhs.m_value || lhs == rhs;
        }

-        template <typename T, typename = std::enable_if_t<std::is_constructible_v<double, T>>>
+        template <typename T, typename = std::enable_if_t<std::is_constructible<double, T>::value>>
        friend bool operator <= ( Approx const& lhs, T const& rhs ) {
            return lhs.m_value < static_cast<double>(rhs) || lhs == rhs;
        }

-        template <typename T, typename = std::enable_if_t<std::is_constructible_v<double, T>>>
+        template <typename T, typename = std::enable_if_t<std::is_constructible<double, T>::value>>
        friend bool operator >= ( T const& lhs, Approx const& rhs ) {
            return static_cast<double>(lhs) > rhs.m_value || lhs == rhs;
        }

-        template <typename T, typename = std::enable_if_t<std::is_constructible_v<double, T>>>
+        template <typename T, typename = std::enable_if_t<std::is_constructible<double, T>::value>>
        friend bool operator >= ( Approx const& lhs, T const& rhs ) {
            return lhs.m_value > static_cast<double>(rhs) || lhs == rhs;
        }

-        template <typename T, typename = std::enable_if_t<std::is_constructible_v<double, T>>>
+        template <typename T, typename = std::enable_if_t<std::is_constructible<double, T>::value>>
        Approx& epsilon( T const& newEpsilon ) {
            const auto epsilonAsDouble = static_cast<double>(newEpsilon);
            setEpsilon(epsilonAsDouble);
            return *this;
        }

-        template <typename T, typename = std::enable_if_t<std::is_constructible_v<double, T>>>
+        template <typename T, typename = std::enable_if_t<std::is_constructible<double, T>::value>>
        Approx& margin( T const& newMargin ) {
            const auto marginAsDouble = static_cast<double>(newMargin);
            setMargin(marginAsDouble);
            return *this;
        }

-        template <typename T, typename = std::enable_if_t<std::is_constructible_v<double, T>>>
+        template <typename T, typename = std::enable_if_t<std::is_constructible<double, T>::value>>
        Approx& scale( T const& newScale ) {
            m_scale = static_cast<double>(newScale);
            return *this;
--- a/src/catch2/catch_assertion_info.hpp
+++ b/src/catch2/catch_assertion_info.hpp
@@ -10,17 +10,16 @@

 #include <catch2/internal/catch_result_type.hpp>
 #include <catch2/internal/catch_source_line_info.hpp>
-
-#include <string_view>
+#include <catch2/internal/catch_stringref.hpp>

 namespace Catch {

    struct AssertionInfo {
        // AssertionInfo() = delete;

-        std::string_view macroName;
+        StringRef macroName;
        SourceLineInfo lineInfo;
-        std::string_view capturedExpression;
+        StringRef capturedExpression;
        ResultDisposition::Flags resultDisposition;
    };

--- a/src/catch2/catch_assertion_result.cpp
+++ b/src/catch2/catch_assertion_result.cpp
@@ -91,14 +91,14 @@ namespace Catch {
                : expr;
    }

-    std::string_view AssertionResult::getMessage() const {
+    StringRef AssertionResult::getMessage() const {
        return m_resultData.message;
    }
    SourceLineInfo AssertionResult::getSourceInfo() const {
        return m_info.lineInfo;
    }

-    std::string_view AssertionResult::getTestMacroName() const {
+    StringRef AssertionResult::getTestMacroName() const {
        return m_info.macroName;
    }

--- a/src/catch2/catch_assertion_result.hpp
+++ b/src/catch2/catch_assertion_result.hpp
@@ -11,6 +11,7 @@
 #include <catch2/catch_assertion_info.hpp>
 #include <catch2/internal/catch_result_type.hpp>
 #include <catch2/internal/catch_source_line_info.hpp>
+#include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_lazy_expr.hpp>

 #include <string>
@@ -45,9 +46,9 @@ namespace Catch {
        std::string getExpressionInMacro() const;
        bool hasExpandedExpression() const;
        std::string getExpandedExpression() const;
-        std::string_view getMessage() const;
+        StringRef getMessage() const;
        SourceLineInfo getSourceInfo() const;
-        std::string_view getTestMacroName() const;
+        StringRef getTestMacroName() const;

    //protected:
        AssertionInfo m_info;
--- a/src/catch2/catch_config.cpp
+++ b/src/catch2/catch_config.cpp
@@ -10,13 +10,13 @@
 #include <catch2/internal/catch_enforce.hpp>
 #include <catch2/internal/catch_parse_numbers.hpp>
 #include <catch2/internal/catch_stdstreams.hpp>
+#include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_string_manip.hpp>
 #include <catch2/internal/catch_test_spec_parser.hpp>
 #include <catch2/interfaces/catch_interfaces_tag_alias_registry.hpp>
 #include <catch2/internal/catch_getenv.hpp>

 #include <fstream>
-#include <optional>

 namespace Catch {

@@ -34,7 +34,7 @@ namespace Catch {
            std::string shardFilePath;
        };

-        static std::optional<bazelShardingOptions> readBazelShardingOptions() {
+        static Optional<bazelShardingOptions> readBazelShardingOptions() {
            const auto bazelShardIndex = Detail::getEnv( "TEST_SHARD_INDEX" );
            const auto bazelShardTotal = Detail::getEnv( "TEST_TOTAL_SHARDS" );
            const auto bazelShardInfoFile = Detail::getEnv( "TEST_SHARD_STATUS_FILE" );
@@ -119,6 +119,8 @@ namespace Catch {
            m_data.reporterSpecifications.push_back( std::move( *parsed ) );
        }

+        // Reading bazel env vars can change some parts of the config data,
+        // so we have to process the bazel env before acting on the config.
        if ( enableBazelEnvSupport() ) {
            readBazelEnvVars();
        }
@@ -142,7 +144,7 @@ namespace Catch {
            // We do the default-output check separately, while always
            // using the default output below to make the code simpler
            // and avoid superfluous copies.
-            if ( !reporterSpec.outputFile() ) {
+            if ( reporterSpec.outputFile().none() ) {
                CATCH_ENFORCE( !defaultOutputUsed,
                               "Internal error: cannot use default output for "
                               "multiple reporters" );
@@ -153,7 +155,7 @@ namespace Catch {
                reporterSpec.name(),
                reporterSpec.outputFile() ? *reporterSpec.outputFile()
                                          : data.defaultOutputFilename,
-                reporterSpec.colourMode().value_or( data.defaultColourMode ),
+                reporterSpec.colourMode().valueOr( data.defaultColourMode ),
                reporterSpec.customOptions() } );
        }
    }
@@ -183,9 +185,11 @@ namespace Catch {

    bool Config::showHelp() const { return m_data.showHelp; }

+    std::string const& Config::getExitGuardFilePath() const { return m_data.prematureExitGuardFilePath; }
+
    // IConfig interface
    bool Config::allowThrows() const                   { return !m_data.noThrow; }
-    std::string_view Config::name() const { return m_data.name.empty() ? m_data.processName : m_data.name; }
+    StringRef Config::name() const { return m_data.name.empty() ? m_data.processName : m_data.name; }
    bool Config::includeSuccessfulResults() const      { return m_data.showSuccessfulTests; }
    bool Config::warnAboutMissingAssertions() const {
        return !!( m_data.warnings & WarnAbout::NoAssertions );
@@ -244,6 +248,11 @@ namespace Catch {
                m_data.shardCount = bazelShardOptions->shardCount;
            }
        }
+
+        const auto bazelExitGuardFile = Detail::getEnv( "TEST_PREMATURE_EXIT_FILE" );
+        if (bazelExitGuardFile) {
+            m_data.prematureExitGuardFilePath = bazelExitGuardFile;
+        }
    }

 } // end namespace Catch
--- a/src/catch2/catch_config.hpp
+++ b/src/catch2/catch_config.hpp
@@ -11,6 +11,8 @@
 #include <catch2/catch_test_spec.hpp>
 #include <catch2/interfaces/catch_interfaces_config.hpp>
 #include <catch2/internal/catch_unique_ptr.hpp>
+#include <catch2/internal/catch_optional.hpp>
+#include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_random_seed_generation.hpp>
 #include <catch2/internal/catch_reporter_spec_parser.hpp>

@@ -85,6 +87,8 @@ namespace Catch {

        std::vector<std::string> testsOrTags;
        std::vector<std::string> sectionsToRun;
+
+        std::string prematureExitGuardFilePath;
    };


@@ -112,9 +116,11 @@ namespace Catch {

        bool showHelp() const;

+        std::string const& getExitGuardFilePath() const;
+
        // IConfig interface
        bool allowThrows() const override;
-        std::string_view name() const override;
+        StringRef name() const override;
        bool includeSuccessfulResults() const override;
        bool warnAboutMissingAssertions() const override;
        bool warnAboutUnmatchedTestSpecs() const override;
--- a/src/catch2/catch_message.cpp
+++ b/src/catch2/catch_message.cpp
@@ -22,7 +22,7 @@ namespace Catch {
        m_messageId( builder.m_info.sequence ) {
        MessageInfo info( CATCH_MOVE( builder.m_info ) );
        info.message = builder.m_stream.str();
-        getResultCapture().pushScopedMessage( CATCH_MOVE(info) );
+        IResultCapture::pushScopedMessage( CATCH_MOVE( info ) );
    }

    ScopedMessage::ScopedMessage( ScopedMessage&& old ) noexcept:
@@ -31,15 +31,14 @@ namespace Catch {
    }

    ScopedMessage::~ScopedMessage() {
-        if ( !m_moved ) { getResultCapture().popScopedMessage( m_messageId ); }
+        if ( !m_moved ) { IResultCapture::popScopedMessage( m_messageId ); }
    }


-    Capturer::Capturer( std::string_view macroName,
+    Capturer::Capturer( StringRef macroName,
                        SourceLineInfo const& lineInfo,
                        ResultWas::OfType resultType,
-                        std::string_view names ):
-        m_resultCapture( getResultCapture() ) {
+                        StringRef names ) {
        auto trimmed = [&] (size_t start, size_t end) {
            while (names[start] == ',' || isspace(static_cast<unsigned char>(names[start]))) {
                ++start;
@@ -86,7 +85,7 @@ namespace Catch {
                if (start != pos && openings.empty()) {
                    m_messages.emplace_back(macroName, lineInfo, resultType);
                    m_messages.back().message += trimmed(start, pos);
-                    m_messages.back().message += " := ";
+                    m_messages.back().message += " := "_sr;
                    start = pos;
                }
                break;
@@ -96,19 +95,19 @@ namespace Catch {
        assert(openings.empty() && "Mismatched openings");
        m_messages.emplace_back(macroName, lineInfo, resultType);
        m_messages.back().message += trimmed(start, names.size() - 1);
-        m_messages.back().message += " := ";
+        m_messages.back().message += " := "_sr;
    }
    Capturer::~Capturer() {
        assert( m_captured == m_messages.size() );
        for (auto const& message : m_messages) {
-            m_resultCapture.popScopedMessage( message.sequence );
+            IResultCapture::popScopedMessage( message.sequence );
        }
    }

    void Capturer::captureValue( size_t index, std::string const& value ) {
        assert( index < m_messages.size() );
        m_messages[index].message += value;
-        m_resultCapture.pushScopedMessage( CATCH_MOVE(m_messages[index]) );
+        IResultCapture::pushScopedMessage( CATCH_MOVE( m_messages[index] ) );
        m_captured++;
    }

--- a/src/catch2/catch_message.hpp
+++ b/src/catch2/catch_message.hpp
@@ -36,7 +36,7 @@ namespace Catch {
    };

    struct MessageBuilder : MessageStream {
-        MessageBuilder( std::string_view macroName,
+        MessageBuilder( StringRef macroName,
                        SourceLineInfo const& lineInfo,
                        ResultWas::OfType type ):
            m_info(macroName, lineInfo, type) {}
@@ -63,10 +63,9 @@ namespace Catch {

    class Capturer {
        std::vector<MessageInfo> m_messages;
-        IResultCapture& m_resultCapture;
        size_t m_captured = 0;
    public:
-        Capturer( std::string_view macroName, SourceLineInfo const& lineInfo, ResultWas::OfType resultType, std::string_view names );
+        Capturer( StringRef macroName, SourceLineInfo const& lineInfo, ResultWas::OfType resultType, StringRef names );

        Capturer(Capturer const&) = delete;
        Capturer& operator=(Capturer const&) = delete;
@@ -92,26 +91,26 @@ namespace Catch {
 ///////////////////////////////////////////////////////////////////////////////
 #define INTERNAL_CATCH_MSG( macroName, messageType, resultDisposition, ... ) \
    do { \
-        Catch::AssertionHandler catchAssertionHandler( macroName, CATCH_INTERNAL_LINEINFO, std::string_view(), resultDisposition ); \
+        Catch::AssertionHandler catchAssertionHandler( macroName##_catch_sr, CATCH_INTERNAL_LINEINFO, Catch::StringRef(), resultDisposition ); \
        catchAssertionHandler.handleMessage( messageType, ( Catch::MessageStream() << __VA_ARGS__ + ::Catch::StreamEndStop() ).m_stream.str() ); \
        catchAssertionHandler.complete(); \
    } while( false )

 ///////////////////////////////////////////////////////////////////////////////
 #define INTERNAL_CATCH_CAPTURE( varName, macroName, ... ) \
-    Catch::Capturer varName( macroName,        \
+    Catch::Capturer varName( macroName##_catch_sr,        \
                             CATCH_INTERNAL_LINEINFO,     \
                             Catch::ResultWas::Info,      \
-                             #__VA_ARGS__ );   \
+                             #__VA_ARGS__##_catch_sr );   \
    varName.captureValues( 0, __VA_ARGS__ )

 ///////////////////////////////////////////////////////////////////////////////
 #define INTERNAL_CATCH_INFO( macroName, log ) \
-    const Catch::ScopedMessage INTERNAL_CATCH_UNIQUE_NAME( scopedMessage )( Catch::MessageBuilder( macroName, CATCH_INTERNAL_LINEINFO, Catch::ResultWas::Info ) << log )
+    const Catch::ScopedMessage INTERNAL_CATCH_UNIQUE_NAME( scopedMessage )( Catch::MessageBuilder( macroName##_catch_sr, CATCH_INTERNAL_LINEINFO, Catch::ResultWas::Info ) << log )

 ///////////////////////////////////////////////////////////////////////////////
 #define INTERNAL_CATCH_UNSCOPED_INFO( macroName, log ) \
-    Catch::getResultCapture().emplaceUnscopedMessage( Catch::MessageBuilder( macroName, CATCH_INTERNAL_LINEINFO, Catch::ResultWas::Info ) << log )
+    Catch::IResultCapture::emplaceUnscopedMessage( Catch::MessageBuilder( macroName##_catch_sr, CATCH_INTERNAL_LINEINFO, Catch::ResultWas::Info ) << log )


 #if defined(CATCH_CONFIG_PREFIX_MESSAGES) && !defined(CATCH_CONFIG_DISABLE)
--- a/src/catch2/catch_section_info.hpp
+++ b/src/catch2/catch_section_info.hpp
@@ -10,6 +10,7 @@

 #include <catch2/internal/catch_move_and_forward.hpp>
 #include <catch2/internal/catch_source_line_info.hpp>
+#include <catch2/internal/catch_stringref.hpp>
 #include <catch2/catch_totals.hpp>

 #include <string>
--- a/src/catch2/catch_session.cpp
+++ b/src/catch2/catch_session.cpp
@@ -26,6 +26,8 @@
 #include <catch2/internal/catch_istream.hpp>

 #include <cassert>
+#include <cstdio>
+#include <cstdlib>
 #include <exception>
 #include <iomanip>
 #include <set>
@@ -140,6 +142,50 @@ namespace Catch {
            }
        }

+        // Creates empty file at path. The path must be writable, we do not
+        // try to create directories in path because that's hard in C++14.
+        void setUpGuardFile( std::string const& guardFilePath ) {
+            if ( !guardFilePath.empty() ) {
+#if defined( _MSC_VER )
+                std::FILE* file = nullptr;
+                if ( fopen_s( &file, guardFilePath.c_str(), "w" ) ) {
+                    char msgBuffer[100];
+                    const auto err = errno;
+                    std::string errMsg;
+                    if ( !strerror_s( msgBuffer, err ) ) {
+                        errMsg = msgBuffer;
+                    } else {
+                        errMsg = "Could not translate errno to a string";
+                    }
+
+#else
+                std::FILE* file = std::fopen( guardFilePath.c_str(), "w" );
+                if ( !file ) {
+                    const auto err = errno;
+                    const char* errMsg = std::strerror( err );
+#endif
+
+                    CATCH_RUNTIME_ERROR( "Could not open the exit guard file '"
+                                         << guardFilePath << "' because '"
+                                         << errMsg << "' (" << err << ')' );
+                }
+                const int ret = std::fclose( file );
+                CATCH_ENFORCE(
+                    ret == 0,
+                    "Error when closing the exit guard file: " << ret );
+            }
+        }
+
+        // Removes file at path. Assuming we created it in setUpGuardFile.
+        void tearDownGuardFile( std::string const& guardFilePath ) {
+            if ( !guardFilePath.empty() ) {
+                const int ret = std::remove( guardFilePath.c_str() );
+                CATCH_ENFORCE(
+                    ret == 0,
+                    "Error when removing the exit guard file: " << ret );
+            }
+        }
+
    } // anon namespace

    Session::Session() {
@@ -258,6 +304,7 @@ namespace Catch {
            static_cast<void>(std::getchar());
        }
        int exitCode = runInternal();
+
        if( ( m_configData.waitForKeypress & WaitForKeypress::BeforeExit ) != 0 ) {
            Catch::cout() << "...waiting for enter/ return before exiting, with code: " << exitCode << '\n' << std::flush;
            static_cast<void>(std::getchar());
@@ -298,6 +345,10 @@ namespace Catch {
        CATCH_TRY {
            config(); // Force config to be constructed

+            // We need to retrieve potential Bazel config with the full Config
+            // constructor, so we have to create the guard file after it is created.
+            setUpGuardFile( m_config->getExitGuardFilePath() );
+
            seedRng( *m_config );

            if (m_configData.filenamesAsTags) {
@@ -327,9 +378,12 @@ namespace Catch {
            TestGroup tests { CATCH_MOVE(reporter), m_config.get() };
            auto const totals = tests.execute();

+            // If we got here, running the tests finished normally-enough.
+            // They might've failed, but that would've been reported elsewhere.
+            tearDownGuardFile( m_config->getExitGuardFilePath() );
+
            if ( tests.hadUnmatchedTestSpecs()
                && m_config->warnAboutUnmatchedTestSpecs() ) {
-                // UnmatchedTestSpecExitCode
                return UnmatchedTestSpecExitCode;
            }

--- a/src/catch2/catch_session.hpp
+++ b/src/catch2/catch_session.hpp
@@ -16,6 +16,7 @@

 namespace Catch {

+    // TODO: Use C++17 `inline` variables
    constexpr int UnspecifiedErrorExitCode = 1;
    constexpr int NoTestsRunExitCode = 2;
    constexpr int UnmatchedTestSpecExitCode = 3;
--- a/src/catch2/catch_test_case_info.cpp
+++ b/src/catch2/catch_test_case_info.cpp
@@ -14,7 +14,6 @@
 #include <cassert>
 #include <cctype>
 #include <algorithm>
-#include <string_view>

 namespace Catch {

@@ -48,28 +47,28 @@ namespace Catch {
            return tcp != TestCaseProperties::None;
        }

-        TestCaseProperties parseSpecialTag( std::string_view tag ) {
+        TestCaseProperties parseSpecialTag( StringRef tag ) {
            if( !tag.empty() && tag[0] == '.' )
                return TestCaseProperties::IsHidden;
-            else if( tag == "!throws" )
+            else if( tag == "!throws"_sr )
                return TestCaseProperties::Throws;
-            else if( tag == "!shouldfail" )
+            else if( tag == "!shouldfail"_sr )
                return TestCaseProperties::ShouldFail;
-            else if( tag == "!mayfail" )
+            else if( tag == "!mayfail"_sr )
                return TestCaseProperties::MayFail;
-            else if( tag == "!nonportable" )
+            else if( tag == "!nonportable"_sr )
                return TestCaseProperties::NonPortable;
-            else if( tag == "!benchmark" )
+            else if( tag == "!benchmark"_sr )
                return TestCaseProperties::Benchmark | TestCaseProperties::IsHidden;
            else
                return TestCaseProperties::None;
        }
-        bool isReservedTag( std::string_view tag ) {
+        bool isReservedTag( StringRef tag ) {
            return parseSpecialTag( tag ) == TestCaseProperties::None
                && tag.size() > 0
                && !std::isalnum( static_cast<unsigned char>(tag[0]) );
        }
-        void enforceNotReservedTag( std::string_view tag, SourceLineInfo const& _lineInfo ) {
+        void enforceNotReservedTag( StringRef tag, SourceLineInfo const& _lineInfo ) {
            CATCH_ENFORCE( !isReservedTag(tag),
                          "Tag name: [" << tag << "] is not allowed.\n"
                          << "Tag names starting with non alphanumeric characters are reserved\n"
@@ -81,13 +80,13 @@ namespace Catch {
            return "Anonymous test case " + std::to_string(++counter);
        }

-        constexpr std::string_view extractFilenamePart(std::string_view filename) {
+        constexpr StringRef extractFilenamePart(StringRef filename) {
            size_t lastDot = filename.size();
            while (lastDot > 0 && filename[lastDot - 1] != '.') {
                --lastDot;
            }
            // In theory we could have filename without any extension in it
-            if ( lastDot == 0 ) { return std::string_view(); }
+            if ( lastDot == 0 ) { return StringRef(); }

            --lastDot;
            size_t nameStart = lastDot;
@@ -99,7 +98,7 @@ namespace Catch {
        }

        // Returns the upper bound on size of extra tags ([#file]+[.])
-        constexpr size_t sizeOfExtraTags(std::string_view filepath) {
+        constexpr size_t sizeOfExtraTags(StringRef filepath) {
            // [.] is 3, [#] is another 3
            const size_t extras = 3 + 3;
            return extractFilenamePart(filepath).size() + extras;
@@ -116,20 +115,20 @@ namespace Catch {
    }

    Detail::unique_ptr<TestCaseInfo>
-        makeTestCaseInfo(std::string_view _className,
+        makeTestCaseInfo(StringRef _className,
                         NameAndTags const& nameAndTags,
                         SourceLineInfo const& _lineInfo ) {
        return Detail::make_unique<TestCaseInfo>(_className, nameAndTags, _lineInfo);
    }

-    TestCaseInfo::TestCaseInfo(std::string_view _className,
+    TestCaseInfo::TestCaseInfo(StringRef _className,
                               NameAndTags const& _nameAndTags,
                               SourceLineInfo const& _lineInfo):
        name( _nameAndTags.name.empty() ? makeDefaultName() : _nameAndTags.name ),
        className( _className ),
        lineInfo( _lineInfo )
    {
-        std::string_view originalTags = _nameAndTags.tags;
+        StringRef originalTags = _nameAndTags.tags;
        // We need to reserve enough space to store all of the tags
        // (including optional hidden tag and filename tag)
        auto requiredSize = originalTags.size() + sizeOfExtraTags(_lineInfo.file);
@@ -164,7 +163,7 @@ namespace Catch {
                // We need to check the tag for special meanings, copy
                // it over to backing storage and actually reference the
                // backing storage in the saved tags
-                std::string_view tagStr = originalTags.substr(tagStart+1, tagEnd - tagStart - 1);
+                StringRef tagStr = originalTags.substr(tagStart+1, tagEnd - tagStart - 1);
                CATCH_ENFORCE( !tagStr.empty(),
                               "Found an empty tag while registering test case '"
                                   << _nameAndTags.name << "' at "
@@ -191,7 +190,7 @@ namespace Catch {

        // Add [.] if relevant
        if (isHidden()) {
-            internalAppendTag(".");
+            internalAppendTag("."_sr);
        }

        // Sort and prepare tags
@@ -236,13 +235,13 @@ namespace Catch {
        return ret;
    }

-    void TestCaseInfo::internalAppendTag(std::string_view tagStr) {
+    void TestCaseInfo::internalAppendTag(StringRef tagStr) {
        backingTags += '[';
        const auto backingStart = backingTags.size();
        backingTags += tagStr;
        const auto backingEnd = backingTags.size();
        backingTags += ']';
-        tags.emplace_back(std::string_view(backingTags.c_str() + backingStart, backingEnd - backingStart));
+        tags.emplace_back(StringRef(backingTags.c_str() + backingStart, backingEnd - backingStart));
    }

    bool operator<( TestCaseInfo const& lhs, TestCaseInfo const& rhs ) {
--- a/src/catch2/catch_test_case_info.hpp
+++ b/src/catch2/catch_test_case_info.hpp
@@ -11,12 +11,12 @@
 #include <catch2/interfaces/catch_interfaces_test_invoker.hpp>
 #include <catch2/internal/catch_source_line_info.hpp>
 #include <catch2/internal/catch_noncopyable.hpp>
+#include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_unique_ptr.hpp>


 #include <cstdint>
 #include <string>
-#include <string_view>
 #include <vector>

 #ifdef __clang__
@@ -34,10 +34,10 @@ namespace Catch {
     * as "cool-tag" internally.
     */
    struct Tag {
-        constexpr Tag(std::string_view original_):
+        constexpr Tag(StringRef original_):
            original(original_)
        {}
-        std::string_view original;
+        StringRef original;

        friend bool operator< ( Tag const& lhs, Tag const& rhs );
        friend bool operator==( Tag const& lhs, Tag const& rhs );
@@ -67,7 +67,7 @@ namespace Catch {
     */
    struct TestCaseInfo : Detail::NonCopyable {

-        TestCaseInfo(std::string_view _className,
+        TestCaseInfo(StringRef _className,
                     NameAndTags const& _nameAndTags,
                     SourceLineInfo const& _lineInfo);

@@ -87,12 +87,12 @@ namespace Catch {
        std::string tagsAsString() const;

        std::string name;
-        std::string_view className;
+        StringRef className;
    private:
        std::string backingTags;
        // Internally we copy tags to the backing storage and then add
        // refs to this storage to the tags vector.
-        void internalAppendTag(std::string_view tagString);
+        void internalAppendTag(StringRef tagString);
    public:
        std::vector<Tag> tags;
        SourceLineInfo lineInfo;
@@ -130,7 +130,7 @@ namespace Catch {
    };

    Detail::unique_ptr<TestCaseInfo>
-    makeTestCaseInfo( std::string_view className,
+    makeTestCaseInfo( StringRef className,
                      NameAndTags const& nameAndTags,
                      SourceLineInfo const& lineInfo );
 }
--- a/src/catch2/catch_test_run_info.hpp
+++ b/src/catch2/catch_test_run_info.hpp
@@ -8,13 +8,13 @@
 #ifndef CATCH_TEST_RUN_INFO_HPP_INCLUDED
 #define CATCH_TEST_RUN_INFO_HPP_INCLUDED

-#include <string_view>
+#include <catch2/internal/catch_stringref.hpp>

 namespace Catch {

    struct TestRunInfo {
-        constexpr TestRunInfo(std::string_view _name) : name(_name) {}
-        std::string_view name;
+        constexpr TestRunInfo(StringRef _name) : name(_name) {}
+        StringRef name;
    };

 } // end namespace Catch
--- a/src/catch2/catch_tostring.cpp
+++ b/src/catch2/catch_tostring.cpp
@@ -13,7 +13,6 @@
 #include <catch2/internal/catch_polyfills.hpp>

 #include <iomanip>
-#include <cstddef>

 namespace Catch {

@@ -58,7 +57,7 @@ namespace Detail {
        }
    } // end unnamed namespace

-    std::string convertIntoString(std::string_view string, bool escapeInvisibles) {
+    std::string convertIntoString(StringRef string, bool escapeInvisibles) {
        std::string ret;
        // This is enough for the "don't escape invisibles" case, and a good
        // lower bound on the "escape invisibles" case.
@@ -96,7 +95,7 @@ namespace Detail {
        return ret;
    }

-    std::string convertIntoString(std::string_view string) {
+    std::string convertIntoString(StringRef string) {
        return convertIntoString(string, getCurrentContext().getConfig()->showInvisibles());
    }

@@ -136,9 +135,11 @@ std::string StringMaker<std::string>::convert(const std::string& str) {
    return Detail::convertIntoString( str );
 }

+#ifdef CATCH_CONFIG_CPP17_STRING_VIEW
 std::string StringMaker<std::string_view>::convert(std::string_view str) {
-    return Detail::convertIntoString( std::string_view( str.data(), str.size() ) );
+    return Detail::convertIntoString( StringRef( str.data(), str.size() ) );
 }
+#endif

 std::string StringMaker<char const*>::convert(char const* str) {
    if (str) {
@@ -165,9 +166,11 @@ std::string StringMaker<std::wstring>::convert(const std::wstring& wstr) {
    return ::Catch::Detail::stringify(s);
 }

+# ifdef CATCH_CONFIG_CPP17_STRING_VIEW
 std::string StringMaker<std::wstring_view>::convert(std::wstring_view str) {
    return StringMaker<std::wstring>::convert(std::wstring(str));
 }
+# endif

 std::string StringMaker<wchar_t const*>::convert(wchar_t const * str) {
    if (str) {
@@ -185,9 +188,12 @@ std::string StringMaker<wchar_t *>::convert(wchar_t * str) {
 }
 #endif

+#if defined(CATCH_CONFIG_CPP17_BYTE)
+#include <cstddef>
 std::string StringMaker<std::byte>::convert(std::byte value) {
    return ::Catch::Detail::stringify(std::to_integer<unsigned long long>(value));
 }
+#endif // defined(CATCH_CONFIG_CPP17_BYTE)

 std::string StringMaker<int>::convert(int value) {
    return ::Catch::Detail::stringify(static_cast<long long>(value));
--- a/src/catch2/catch_tostring.hpp
+++ b/src/catch2/catch_tostring.hpp
@@ -20,7 +20,9 @@
 #include <catch2/internal/catch_void_type.hpp>
 #include <catch2/interfaces/catch_interfaces_enum_values_registry.hpp>

+#ifdef CATCH_CONFIG_CPP17_STRING_VIEW
 #include <string_view>
+#endif

 #ifdef _MSC_VER
 #pragma warning(push)
@@ -46,14 +48,14 @@ namespace Catch {
            return n;
        }

-        constexpr std::string_view unprintableString = "{?}";
+        constexpr StringRef unprintableString = "{?}"_sr;

        //! Encases `string in quotes, and optionally escapes invisibles
-        std::string convertIntoString( std::string_view string, bool escapeInvisibles );
+        std::string convertIntoString( StringRef string, bool escapeInvisibles );

        //! Encases `string` in quotes, and escapes invisibles if user requested
        //! it via CLI
-        std::string convertIntoString( std::string_view string );
+        std::string convertIntoString( StringRef string );

        std::string rawMemoryToString( const void *object, std::size_t size );

@@ -76,13 +78,13 @@ namespace Catch {

        template<typename T>
        std::enable_if_t<
-            !std::is_enum_v<T> && !std::is_base_of_v<std::exception, T>,
+            !std::is_enum<T>::value && !std::is_base_of<std::exception, T>::value,
        std::string> convertUnstreamable( T const& ) {
            return std::string(Detail::unprintableString);
        }
        template<typename T>
        std::enable_if_t<
-            !std::is_enum_v<T> && std::is_base_of_v<std::exception, T>,
+            !std::is_enum<T>::value && std::is_base_of<std::exception, T>::value,
         std::string> convertUnstreamable(T const& ex) {
            return ex.what();
        }
@@ -90,7 +92,7 @@ namespace Catch {

        template<typename T>
        std::enable_if_t<
-            std::is_enum_v<T>,
+            std::is_enum<T>::value,
        std::string> convertUnstreamable( T const& value ) {
            return convertUnknownEnumToString( value );
        }
@@ -171,10 +173,12 @@ namespace Catch {
        static std::string convert(const std::string& str);
    };

+#ifdef CATCH_CONFIG_CPP17_STRING_VIEW
    template<>
    struct StringMaker<std::string_view> {
        static std::string convert(std::string_view str);
    };
+#endif

    template<>
    struct StringMaker<char const *> {
@@ -191,10 +195,12 @@ namespace Catch {
        static std::string convert(const std::wstring& wstr);
    };

+# ifdef CATCH_CONFIG_CPP17_STRING_VIEW
    template<>
    struct StringMaker<std::wstring_view> {
        static std::string convert(std::wstring_view str);
    };
+# endif

    template<>
    struct StringMaker<wchar_t const *> {
@@ -210,7 +216,7 @@ namespace Catch {
    struct StringMaker<char[SZ]> {
        static std::string convert(char const* str) {
            return Detail::convertIntoString(
-                std::string_view( str, Detail::catch_strnlen( str, SZ ) ) );
+                StringRef( str, Detail::catch_strnlen( str, SZ ) ) );
        }
    };
    template<size_t SZ>
@@ -218,7 +224,7 @@ namespace Catch {
        static std::string convert(signed char const* str) {
            auto reinterpreted = reinterpret_cast<char const*>(str);
            return Detail::convertIntoString(
-                std::string_view(reinterpreted, Detail::catch_strnlen(reinterpreted, SZ)));
+                StringRef(reinterpreted, Detail::catch_strnlen(reinterpreted, SZ)));
        }
    };
    template<size_t SZ>
@@ -226,14 +232,16 @@ namespace Catch {
        static std::string convert(unsigned char const* str) {
            auto reinterpreted = reinterpret_cast<char const*>(str);
            return Detail::convertIntoString(
-                std::string_view(reinterpreted, Detail::catch_strnlen(reinterpreted, SZ)));
+                StringRef(reinterpreted, Detail::catch_strnlen(reinterpreted, SZ)));
        }
    };

+#if defined(CATCH_CONFIG_CPP17_BYTE)
    template<>
    struct StringMaker<std::byte> {
        static std::string convert(std::byte value);
    };
+#endif // defined(CATCH_CONFIG_CPP17_BYTE)
    template<>
    struct StringMaker<int> {
        static std::string convert(int value);
@@ -379,7 +387,7 @@ namespace Catch {
 }
 #endif // CATCH_CONFIG_ENABLE_PAIR_STRINGMAKER

-#if defined(CATCH_CONFIG_ENABLE_OPTIONAL_STRINGMAKER)
+#if defined(CATCH_CONFIG_ENABLE_OPTIONAL_STRINGMAKER) && defined(CATCH_CONFIG_CPP17_OPTIONAL)
 #include <optional>
 namespace Catch {
    template<typename T>
@@ -409,7 +417,7 @@ namespace Catch {
        template<
            typename Tuple,
            std::size_t N = 0,
-            bool = (N < std::tuple_size_v<Tuple>)
+            bool = (N < std::tuple_size<Tuple>::value)
            >
            struct TupleElementPrinter {
            static void print(const Tuple& tuple, std::ostream& os) {
@@ -443,7 +451,7 @@ namespace Catch {
 }
 #endif // CATCH_CONFIG_ENABLE_TUPLE_STRINGMAKER

-#if defined(CATCH_CONFIG_ENABLE_VARIANT_STRINGMAKER)
+#if defined(CATCH_CONFIG_ENABLE_VARIANT_STRINGMAKER) && defined(CATCH_CONFIG_CPP17_VARIANT)
 #include <variant>
 namespace Catch {
    template<>
--- a/src/catch2/catch_user_config.hpp.in
+++ b/src/catch2/catch_user_config.hpp.in
@@ -60,6 +60,56 @@



+#cmakedefine CATCH_CONFIG_CPP17_BYTE
+#cmakedefine CATCH_CONFIG_NO_CPP17_BYTE
+
+#if defined( CATCH_CONFIG_CPP17_BYTE ) && \
+    defined( CATCH_CONFIG_NO_CPP17_BYTE )
+#    error Cannot force CPP17_BYTE to both ON and OFF
+#endif
+
+
+
+#cmakedefine CATCH_CONFIG_CPP17_OPTIONAL
+#cmakedefine CATCH_CONFIG_NO_CPP17_OPTIONAL
+
+#if defined( CATCH_CONFIG_CPP17_OPTIONAL ) && \
+    defined( CATCH_CONFIG_NO_CPP17_OPTIONAL )
+#    error Cannot force CPP17_OPTIONAL to both ON and OFF
+#endif
+
+
+
+#cmakedefine CATCH_CONFIG_CPP17_STRING_VIEW
+#cmakedefine CATCH_CONFIG_NO_CPP17_STRING_VIEW
+
+#if defined( CATCH_CONFIG_CPP17_STRING_VIEW ) && \
+    defined( CATCH_CONFIG_NO_CPP17_STRING_VIEW )
+#    error Cannot force CPP17_STRING_VIEW to both ON and OFF
+#endif
+
+
+
+#cmakedefine CATCH_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS
+#cmakedefine CATCH_CONFIG_NO_CPP17_UNCAUGHT_EXCEPTIONS
+
+#if defined( CATCH_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS ) && \
+    defined( CATCH_CONFIG_NO_CPP17_UNCAUGHT_EXCEPTIONS )
+#    error Cannot force CPP17_UNCAUGHT_EXCEPTIONS to both ON and OFF
+#endif
+
+
+
+#cmakedefine CATCH_CONFIG_CPP17_VARIANT
+#cmakedefine CATCH_CONFIG_NO_CPP17_VARIANT
+
+#if defined( CATCH_CONFIG_CPP17_VARIANT ) && \
+    defined( CATCH_CONFIG_NO_CPP17_VARIANT )
+#    error Cannot force CPP17_VARIANT to both ON and OFF
+#endif
+
+
+
 #cmakedefine CATCH_CONFIG_GLOBAL_NEXTAFTER
 #cmakedefine CATCH_CONFIG_NO_GLOBAL_NEXTAFTER

--- a/src/catch2/generators/catch_generators.cpp
+++ b/src/catch2/generators/catch_generators.cpp
@@ -27,11 +27,11 @@ namespace Detail {

    GeneratorUntypedBase::~GeneratorUntypedBase() = default;

-    IGeneratorTracker* acquireGeneratorTracker(std::string_view generatorName, SourceLineInfo const& lineInfo ) {
+    IGeneratorTracker* acquireGeneratorTracker(StringRef generatorName, SourceLineInfo const& lineInfo ) {
        return getResultCapture().acquireGeneratorTracker( generatorName, lineInfo );
    }

-    IGeneratorTracker* createGeneratorTracker( std::string_view generatorName,
+    IGeneratorTracker* createGeneratorTracker( StringRef generatorName,
                                 SourceLineInfo lineInfo,
                                 GeneratorBasePtr&& generator ) {
        return getResultCapture().createGeneratorTracker(
--- a/src/catch2/generators/catch_generators.hpp
+++ b/src/catch2/generators/catch_generators.hpp
@@ -11,6 +11,7 @@
 #include <catch2/catch_tostring.hpp>
 #include <catch2/interfaces/catch_interfaces_generatortracker.hpp>
 #include <catch2/internal/catch_source_line_info.hpp>
+#include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_move_and_forward.hpp>
 #include <catch2/internal/catch_unique_name.hpp>

@@ -87,7 +88,7 @@ namespace Detail {

    template<typename T>
    class FixedValuesGenerator final : public IGenerator<T> {
-        static_assert(!std::is_same_v<T, bool>,
+        static_assert(!std::is_same<T, bool>::value,
            "FixedValuesGenerator does not support bools because of std::vector<bool>"
            "specialization, use SingleValue Generator instead.");
        std::vector<T> m_values;
@@ -130,7 +131,7 @@ namespace Detail {
            m_generators.emplace_back( value( CATCH_MOVE( val ) ) );
        }
        template <typename U>
-        std::enable_if_t<!std::is_same_v<std::decay_t<U>, T>>
+        std::enable_if_t<!std::is_same<std::decay_t<U>, T>::value>
        add_generator( U&& val ) {
            add_generator( T( CATCH_FORWARD( val ) ) );
        }
@@ -196,14 +197,14 @@ namespace Detail {
        return makeGenerators( value( T( CATCH_FORWARD( val ) ) ), CATCH_FORWARD( moreGenerators )... );
    }

-    IGeneratorTracker* acquireGeneratorTracker( std::string_view generatorName,
+    IGeneratorTracker* acquireGeneratorTracker( StringRef generatorName,
                                                SourceLineInfo const& lineInfo );
-    IGeneratorTracker* createGeneratorTracker( std::string_view generatorName,
+    IGeneratorTracker* createGeneratorTracker( StringRef generatorName,
                                               SourceLineInfo lineInfo,
                                               GeneratorBasePtr&& generator );

    template<typename L>
-    auto generate( std::string_view generatorName, SourceLineInfo const& lineInfo, L const& generatorExpression ) -> typename decltype(generatorExpression())::type {
+    auto generate( StringRef generatorName, SourceLineInfo const& lineInfo, L const& generatorExpression ) -> typename decltype(generatorExpression())::type {
        using UnderlyingType = typename decltype(generatorExpression())::type;

        IGeneratorTracker* tracker = acquireGeneratorTracker( generatorName, lineInfo );
@@ -224,7 +225,7 @@ namespace Detail {
 } // namespace Generators
 } // namespace Catch

-#define CATCH_INTERNAL_GENERATOR_STRINGIZE_IMPL( ... ) #__VA_ARGS__
+#define CATCH_INTERNAL_GENERATOR_STRINGIZE_IMPL( ... ) #__VA_ARGS__##_catch_sr
 #define CATCH_INTERNAL_GENERATOR_STRINGIZE(...) CATCH_INTERNAL_GENERATOR_STRINGIZE_IMPL(__VA_ARGS__)

 #define GENERATE( ... ) \
--- a/src/catch2/generators/catch_generators_adapters.hpp
+++ b/src/catch2/generators/catch_generators_adapters.hpp
@@ -58,7 +58,7 @@ namespace Generators {
    class FilterGenerator final : public IGenerator<T> {
        GeneratorWrapper<T> m_generator;
        Predicate m_predicate;
-        static_assert(!std::is_reference_v<Predicate>, "This would most likely result in a dangling reference");
+        static_assert(!std::is_reference<Predicate>::value, "This would most likely result in a dangling reference");
    public:
        template <typename P>
        FilterGenerator(P&& pred, GeneratorWrapper<T>&& generator):
@@ -97,7 +97,7 @@ namespace Generators {

    template <typename T>
    class RepeatGenerator final : public IGenerator<T> {
-        static_assert(!std::is_same_v<T, bool>,
+        static_assert(!std::is_same<T, bool>::value,
            "RepeatGenerator currently does not support bools"
            "because of std::vector<bool> specialization");
        GeneratorWrapper<T> m_generator;
--- a/src/catch2/generators/catch_generators_random.hpp
+++ b/src/catch2/generators/catch_generators_random.hpp
@@ -83,7 +83,7 @@ public:
 };

 template <typename T>
-std::enable_if_t<std::is_integral_v<T>, GeneratorWrapper<T>>
+std::enable_if_t<std::is_integral<T>::value, GeneratorWrapper<T>>
 random(T a, T b) {
    return GeneratorWrapper<T>(
        Catch::Detail::make_unique<RandomIntegerGenerator<T>>(a, b, Detail::getSeed())
@@ -91,7 +91,7 @@ random(T a, T b) {
 }

 template <typename T>
-std::enable_if_t<std::is_floating_point_v<T>,
+std::enable_if_t<std::is_floating_point<T>::value,
 GeneratorWrapper<T>>
 random(T a, T b) {
    return GeneratorWrapper<T>(
--- a/src/catch2/generators/catch_generators_range.hpp
+++ b/src/catch2/generators/catch_generators_range.hpp
@@ -52,20 +52,20 @@ public:

 template <typename T>
 GeneratorWrapper<T> range(T const& start, T const& end, T const& step) {
-    static_assert(std::is_arithmetic_v<T> && !std::is_same_v<T, bool>, "Type must be numeric");
+    static_assert(std::is_arithmetic<T>::value && !std::is_same<T, bool>::value, "Type must be numeric");
    return GeneratorWrapper<T>(Catch::Detail::make_unique<RangeGenerator<T>>(start, end, step));
 }

 template <typename T>
 GeneratorWrapper<T> range(T const& start, T const& end) {
-    static_assert(std::is_integral_v<T> && !std::is_same_v<T, bool>, "Type must be an integer");
+    static_assert(std::is_integral<T>::value && !std::is_same<T, bool>::value, "Type must be an integer");
    return GeneratorWrapper<T>(Catch::Detail::make_unique<RangeGenerator<T>>(start, end));
 }


 template <typename T>
 class IteratorGenerator final : public IGenerator<T> {
-    static_assert(!std::is_same_v<T, bool>,
+    static_assert(!std::is_same<T, bool>::value,
        "IteratorGenerator currently does not support bools"
        "because of std::vector<bool> specialization");

--- a/src/catch2/interfaces/catch_interfaces_capture.hpp
+++ b/src/catch2/interfaces/catch_interfaces_capture.hpp
@@ -10,6 +10,7 @@

 #include <string>

+#include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_result_type.hpp>
 #include <catch2/internal/catch_unique_ptr.hpp>
 #include <catch2/benchmark/detail/catch_benchmark_stats_fwd.hpp>
@@ -42,31 +43,30 @@ namespace Catch {
        virtual ~IResultCapture();

        virtual void notifyAssertionStarted( AssertionInfo const& info ) = 0;
-        virtual bool sectionStarted( std::string_view sectionName,
+        virtual bool sectionStarted( StringRef sectionName,
                                     SourceLineInfo const& sectionLineInfo,
                                     Counts& assertions ) = 0;
        virtual void sectionEnded( SectionEndInfo&& endInfo ) = 0;
        virtual void sectionEndedEarly( SectionEndInfo&& endInfo ) = 0;

        virtual IGeneratorTracker*
-        acquireGeneratorTracker( std::string_view generatorName,
+        acquireGeneratorTracker( StringRef generatorName,
                                 SourceLineInfo const& lineInfo ) = 0;
        virtual IGeneratorTracker*
-        createGeneratorTracker( std::string_view generatorName,
+        createGeneratorTracker( StringRef generatorName,
                                SourceLineInfo lineInfo,
                                Generators::GeneratorBasePtr&& generator ) = 0;

-        virtual void benchmarkPreparing( std::string_view name ) = 0;
+        virtual void benchmarkPreparing( StringRef name ) = 0;
        virtual void benchmarkStarting( BenchmarkInfo const& info ) = 0;
        virtual void benchmarkEnded( BenchmarkStats<> const& stats ) = 0;
-        virtual void benchmarkFailed( std::string_view error ) = 0;
+        virtual void benchmarkFailed( StringRef error ) = 0;

-        virtual void pushScopedMessage( MessageInfo&& message ) = 0;
-        virtual void popScopedMessage( unsigned int messageId ) = 0;
+        static void pushScopedMessage( MessageInfo&& message );
+        static void popScopedMessage( unsigned int messageId );
+        static void emplaceUnscopedMessage( MessageBuilder&& builder );

-        virtual void emplaceUnscopedMessage( MessageBuilder&& builder ) = 0;
-
-        virtual void handleFatalErrorCondition( std::string_view message ) = 0;
+        virtual void handleFatalErrorCondition( StringRef message ) = 0;

        virtual void handleExpr
                (   AssertionInfo const& info,
@@ -101,6 +101,7 @@ namespace Catch {
    };

    IResultCapture& getResultCapture();
+
 }

 #endif // CATCH_INTERFACES_CAPTURE_HPP_INCLUDED
--- a/src/catch2/interfaces/catch_interfaces_config.hpp
+++ b/src/catch2/interfaces/catch_interfaces_config.hpp
@@ -9,6 +9,7 @@
 #define CATCH_INTERFACES_CONFIG_HPP_INCLUDED

 #include <catch2/internal/catch_noncopyable.hpp>
+#include <catch2/internal/catch_stringref.hpp>

 #include <chrono>
 #include <string>
@@ -65,7 +66,7 @@ namespace Catch {
        virtual ~IConfig();

        virtual bool allowThrows() const = 0;
-        virtual std::string_view name() const = 0;
+        virtual StringRef name() const = 0;
        virtual bool includeSuccessfulResults() const = 0;
        virtual bool shouldDebugBreak() const = 0;
        virtual bool warnAboutMissingAssertions() const = 0;
--- a/src/catch2/interfaces/catch_interfaces_enum_values_registry.hpp
+++ b/src/catch2/interfaces/catch_interfaces_enum_values_registry.hpp
@@ -8,19 +8,20 @@
 #ifndef CATCH_INTERFACES_ENUM_VALUES_REGISTRY_HPP_INCLUDED
 #define CATCH_INTERFACES_ENUM_VALUES_REGISTRY_HPP_INCLUDED

-#include <string_view>
+#include <catch2/internal/catch_stringref.hpp>
+
 #include <vector>

 namespace Catch {

    namespace Detail {
        struct EnumInfo {
-            std::string_view m_name;
-            std::vector<std::pair<int, std::string_view>> m_values;
+            StringRef m_name;
+            std::vector<std::pair<int, StringRef>> m_values;

            ~EnumInfo();

-            std::string_view lookup( int value ) const;
+            StringRef lookup( int value ) const;
        };
    } // namespace Detail

@@ -28,10 +29,10 @@ namespace Catch {
    public:
        virtual ~IMutableEnumValuesRegistry(); // = default;

-        virtual Detail::EnumInfo const& registerEnum( std::string_view enumName, std::string_view allEnums, std::vector<int> const& values ) = 0;
+        virtual Detail::EnumInfo const& registerEnum( StringRef enumName, StringRef allEnums, std::vector<int> const& values ) = 0;

        template<typename E>
-        Detail::EnumInfo const& registerEnum( std::string_view enumName, std::string_view allEnums, std::initializer_list<E> values ) {
+        Detail::EnumInfo const& registerEnum( StringRef enumName, StringRef allEnums, std::initializer_list<E> values ) {
            static_assert(sizeof(int) >= sizeof(E), "Cannot serialize enum to int");
            std::vector<int> intValues;
            intValues.reserve( values.size() );
--- a/src/catch2/interfaces/catch_interfaces_generatortracker.cpp
+++ b/src/catch2/interfaces/catch_interfaces_generatortracker.cpp
@@ -21,7 +21,7 @@ namespace Catch {
            return ret;
        }

-        std::string_view GeneratorUntypedBase::currentElementAsString() const {
+        StringRef GeneratorUntypedBase::currentElementAsString() const {
            if ( m_stringReprCache.empty() ) {
                m_stringReprCache = stringifyImpl();
            }
--- a/src/catch2/interfaces/catch_interfaces_generatortracker.hpp
+++ b/src/catch2/interfaces/catch_interfaces_generatortracker.hpp
@@ -9,6 +9,7 @@
 #define CATCH_INTERFACES_GENERATORTRACKER_HPP_INCLUDED

 #include <catch2/internal/catch_unique_ptr.hpp>
+#include <catch2/internal/catch_stringref.hpp>

 #include <string>

@@ -70,7 +71,7 @@ namespace Catch {
             * is destructed, or it moves onto the next element, whichever
             * comes first.
             */
-            std::string_view currentElementAsString() const;
+            StringRef currentElementAsString() const;
        };
        using GeneratorBasePtr = Catch::Detail::unique_ptr<GeneratorUntypedBase>;

--- a/src/catch2/interfaces/catch_interfaces_reporter.hpp
+++ b/src/catch2/interfaces/catch_interfaces_reporter.hpp
@@ -13,6 +13,7 @@
 #include <catch2/catch_totals.hpp>
 #include <catch2/catch_assertion_result.hpp>
 #include <catch2/internal/catch_message_info.hpp>
+#include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_unique_ptr.hpp>
 #include <catch2/benchmark/detail/catch_benchmark_stats.hpp>

@@ -153,9 +154,9 @@ namespace Catch {
        }

        //! Called when no test cases match provided test spec
-        virtual void noMatchingTestCases( std::string_view unmatchedSpec ) = 0;
+        virtual void noMatchingTestCases( StringRef unmatchedSpec ) = 0;
        //! Called for all invalid test specs from the cli
-        virtual void reportInvalidTestSpec( std::string_view invalidArgument ) = 0;
+        virtual void reportInvalidTestSpec( StringRef invalidArgument ) = 0;

        /**
         * Called once in a testing run before tests are started
@@ -172,13 +173,13 @@ namespace Catch {
        virtual void sectionStarting( SectionInfo const& sectionInfo ) = 0;

        //! Called when user-code is being probed before the actual benchmark runs
-        virtual void benchmarkPreparing( std::string_view benchmarkName ) = 0;
+        virtual void benchmarkPreparing( StringRef benchmarkName ) = 0;
        //! Called after probe but before the user-code is being benchmarked
        virtual void benchmarkStarting( BenchmarkInfo const& benchmarkInfo ) = 0;
        //! Called with the benchmark results if benchmark successfully finishes
        virtual void benchmarkEnded( BenchmarkStats<> const& benchmarkStats ) = 0;
        //! Called if running the benchmarks fails for any reason
-        virtual void benchmarkFailed( std::string_view benchmarkName ) = 0;
+        virtual void benchmarkFailed( StringRef benchmarkName ) = 0;

        //! Called before assertion success/failure is evaluated
        virtual void assertionStarting( AssertionInfo const& assertionInfo ) = 0;
@@ -208,7 +209,7 @@ namespace Catch {
        virtual void skipTest( TestCaseInfo const& testInfo ) = 0;

        //! Called if a fatal error (signal/structured exception) occurred
-        virtual void fatalErrorEncountered( std::string_view error ) = 0;
+        virtual void fatalErrorEncountered( StringRef error ) = 0;

        //! Writes out information about provided reporters using reporter-specific format
        virtual void listReporters(std::vector<ReporterDescription> const& descriptions) = 0;
--- a/src/catch2/interfaces/catch_interfaces_reporter_factory.hpp
+++ b/src/catch2/interfaces/catch_interfaces_reporter_factory.hpp
@@ -9,6 +9,7 @@
 #define CATCH_INTERFACES_REPORTER_FACTORY_HPP_INCLUDED

 #include <catch2/internal/catch_unique_ptr.hpp>
+#include <catch2/internal/catch_stringref.hpp>

 #include <string>

@@ -35,7 +36,7 @@ namespace Catch {
        virtual ~EventListenerFactory(); // = default
        virtual IEventListenerPtr create( IConfig const* config ) const = 0;
        //! Return a meaningful name for the listener, e.g. its type name
-        virtual std::string_view getName() const = 0;
+        virtual StringRef getName() const = 0;
        //! Return listener's description if available
        virtual std::string getDescription() const = 0;
    };
--- a/src/catch2/internal/catch_assertion_handler.cpp
+++ b/src/catch2/internal/catch_assertion_handler.cpp
@@ -15,9 +15,9 @@
 namespace Catch {

    AssertionHandler::AssertionHandler
-        (   std::string_view macroName,
+        (   StringRef macroName,
            SourceLineInfo const& lineInfo,
-            std::string_view capturedExpression,
+            StringRef capturedExpression,
            ResultDisposition::Flags resultDisposition )
    :   m_assertionInfo{ macroName, lineInfo, capturedExpression, resultDisposition },
        m_resultCapture( getResultCapture() )
--- a/src/catch2/internal/catch_assertion_handler.hpp
+++ b/src/catch2/internal/catch_assertion_handler.hpp
@@ -30,9 +30,9 @@ namespace Catch {

    public:
        AssertionHandler
-            (   std::string_view macroName,
+            (   StringRef macroName,
                SourceLineInfo const& lineInfo,
-                std::string_view capturedExpression,
+                StringRef capturedExpression,
                ResultDisposition::Flags resultDisposition );
        ~AssertionHandler() {
            if ( !m_completed ) {
--- a/src/catch2/internal/catch_case_insensitive_comparisons.cpp
+++ b/src/catch2/internal/catch_case_insensitive_comparisons.cpp
@@ -14,8 +14,8 @@
 namespace Catch {
    namespace Detail {

-        bool CaseInsensitiveLess::operator()( std::string_view lhs,
-                                              std::string_view rhs ) const {
+        bool CaseInsensitiveLess::operator()( StringRef lhs,
+                                              StringRef rhs ) const {
            return std::lexicographical_compare(
                lhs.begin(), lhs.end(),
                rhs.begin(), rhs.end(),
@@ -23,8 +23,8 @@ namespace Catch {
        }

        bool
-        CaseInsensitiveEqualTo::operator()( std::string_view lhs,
-                                            std::string_view rhs ) const {
+        CaseInsensitiveEqualTo::operator()( StringRef lhs,
+                                            StringRef rhs ) const {
            return std::equal(
                lhs.begin(), lhs.end(),
                rhs.begin(), rhs.end(),
--- a/src/catch2/internal/catch_case_insensitive_comparisons.hpp
+++ b/src/catch2/internal/catch_case_insensitive_comparisons.hpp
@@ -8,20 +8,20 @@
 #ifndef CATCH_CASE_INSENSITIVE_COMPARISONS_HPP_INCLUDED
 #define CATCH_CASE_INSENSITIVE_COMPARISONS_HPP_INCLUDED

-#include <string_view>
+#include <catch2/internal/catch_stringref.hpp>

 namespace Catch {
    namespace Detail {
        //! Provides case-insensitive `op<` semantics when called
        struct CaseInsensitiveLess {
-            bool operator()( std::string_view lhs,
-                             std::string_view rhs ) const;
+            bool operator()( StringRef lhs,
+                             StringRef rhs ) const;
        };

        //! Provides case-insensitive `op==` semantics when called
        struct CaseInsensitiveEqualTo {
-            bool operator()( std::string_view lhs,
-                             std::string_view rhs ) const;
+            bool operator()( StringRef lhs,
+                             StringRef rhs ) const;
        };

    } // namespace Detail
--- a/src/catch2/internal/catch_clara.cpp
+++ b/src/catch2/internal/catch_clara.cpp
@@ -25,7 +25,7 @@ namespace {
            ;
    }

-    std::string_view normaliseOpt( std::string_view optName ) {
+    Catch::StringRef normaliseOpt( Catch::StringRef optName ) {
        if ( optName[0] == '-'
 #if defined(CATCH_PLATFORM_WINDOWS)
             || optName[0] == '/'
@@ -37,7 +37,7 @@ namespace {
        return optName;
    }

-    static size_t find_first_separator(std::string_view sr) {
+    static size_t find_first_separator(Catch::StringRef sr) {
        auto is_separator = []( char c ) {
            return c == ' ' || c == ':' || c == '=';
        };
@@ -47,7 +47,7 @@ namespace {
            ++pos;
        }

-        return std::string_view::npos;
+        return Catch::StringRef::npos;
    }

 } // namespace
@@ -65,10 +65,10 @@ namespace Catch {
                }

                if ( it != itEnd ) {
-                    std::string_view next = *it;
+                    StringRef next = *it;
                    if ( isOptPrefix( next[0] ) ) {
                        auto delimiterPos = find_first_separator(next);
-                        if ( delimiterPos != std::string_view::npos ) {
+                        if ( delimiterPos != StringRef::npos ) {
                            m_tokenBuffer.push_back(
                                { TokenType::Option,
                                  next.substr( 0, delimiterPos ) } );
@@ -205,7 +205,7 @@ namespace Catch {
            return { oss.str(), m_description };
        }

-        bool Opt::isMatch(std::string_view optToken) const {
+        bool Opt::isMatch(StringRef optToken) const {
            auto normalisedToken = normaliseOpt(optToken);
            for (auto const& name : m_optNames) {
                if (normaliseOpt(name) == normalisedToken)
@@ -243,12 +243,12 @@ namespace Catch {
                        if (!tokens)
                            return Detail::InternalParseResult::runtimeError(
                                "Expected argument following " +
-                                std::string(token.token));
+                                token.token);
                        auto const& argToken = *tokens;
                        if (argToken.type != Detail::TokenType::Argument)
                            return Detail::InternalParseResult::runtimeError(
                                "Expected argument following " +
-                                std::string(token.token));
+                                token.token);
                        const auto result = valueRef->setValue(static_cast<std::string>(argToken.token));
                        if (!result)
                            return Detail::InternalParseResult(result);
@@ -436,7 +436,7 @@ namespace Catch {
                if ( !tokenParsed )
                    return Detail::InternalParseResult::runtimeError(
                        "Unrecognised token: " +
-                        std::string(result.value().remainingTokens()->token) );
+                        result.value().remainingTokens()->token );
            }
            // !TBD Check missing required options
            return result;
@@ -445,7 +445,7 @@ namespace Catch {
        Args::Args(int argc, char const* const* argv) :
            m_exeName(argv[0]), m_args(argv + 1, argv + argc) {}

-        Args::Args(std::initializer_list<std::string_view> args) :
+        Args::Args(std::initializer_list<StringRef> args) :
            m_exeName(*args.begin()),
            m_args(args.begin() + 1, args.end()) {}

--- a/src/catch2/internal/catch_clara.hpp
+++ b/src/catch2/internal/catch_clara.hpp
@@ -20,8 +20,16 @@
 #    pragma GCC diagnostic ignored "-Wsign-conversion"
 #endif

-#include <optional>
+#ifndef CLARA_CONFIG_OPTIONAL_TYPE
+#    ifdef __has_include
+#        if __has_include( <optional>) && __cplusplus >= 201703L
+#            include <optional>
+#            define CLARA_CONFIG_OPTIONAL_TYPE std::optional
+#        endif
+#    endif
+#endif

+#include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_move_and_forward.hpp>
 #include <catch2/internal/catch_noncopyable.hpp>
 #include <catch2/internal/catch_void_type.hpp>
@@ -92,13 +100,13 @@ namespace Catch {
            enum class TokenType { Option, Argument };
            struct Token {
                TokenType type;
-                std::string_view token;
+                StringRef token;
            };

            // Abstracts iterators into args as a stream of tokens, with option
            // arguments uniformly handled
            class TokenStream {
-                using Iterator = std::vector<std::string_view>::const_iterator;
+                using Iterator = std::vector<StringRef>::const_iterator;
                Iterator it;
                Iterator itEnd;
                std::vector<Token> m_tokenBuffer;
@@ -301,7 +309,7 @@ namespace Catch {

            struct HelpColumns {
                std::string left;
-                std::string_view descriptions;
+                StringRef descriptions;
            };

            template <typename T>
@@ -320,9 +328,10 @@ namespace Catch {
                                      std::string& target );
            ParserResult convertInto( std::string const& source, bool& target );

+#ifdef CLARA_CONFIG_OPTIONAL_TYPE
            template <typename T>
            auto convertInto( std::string const& source,
-                              std::optional<T>& target )
+                              CLARA_CONFIG_OPTIONAL_TYPE<T>& target )
                -> ParserResult {
                T temp;
                auto result = convertInto( source, temp );
@@ -330,6 +339,7 @@ namespace Catch {
                    target = CATCH_MOVE( temp );
                return result;
            }
+#endif // CLARA_CONFIG_OPTIONAL_TYPE

            struct BoundRef : Catch::Detail::NonCopyable {
                virtual ~BoundRef() = default;
@@ -383,7 +393,7 @@ namespace Catch {

            template <typename ReturnType> struct LambdaInvoker {
                static_assert(
-                    std::is_same_v<ReturnType, ParserResult>,
+                    std::is_same<ReturnType, ParserResult>::value,
                    "Lambda must return void or clara::ParserResult" );

                template <typename L, typename ArgType>
@@ -439,8 +449,8 @@ namespace Catch {
                    UnaryLambdaTraits<L>::isValid,
                    "Supplied lambda must take exactly one argument" );
                static_assert(
-                    std::is_same_v<typename UnaryLambdaTraits<L>::ArgType,
-                                   bool>,
+                    std::is_same<typename UnaryLambdaTraits<L>::ArgType,
+                                 bool>::value,
                    "flags must be boolean" );

                explicit BoundFlagLambda( L const& lambda ):
@@ -479,8 +489,8 @@ namespace Catch {
            protected:
                Optionality m_optionality = Optionality::Optional;
                std::shared_ptr<BoundRef> m_ref;
-                std::string_view m_hint;
-                std::string_view m_description;
+                StringRef m_hint;
+                StringRef m_description;

                explicit ParserRefImpl( std::shared_ptr<BoundRef> const& ref ):
                    m_ref( ref ) {}
@@ -489,29 +499,29 @@ namespace Catch {
                template <typename LambdaT>
                ParserRefImpl( accept_many_t,
                               LambdaT const& ref,
-                               std::string_view hint ):
+                               StringRef hint ):
                    m_ref( std::make_shared<BoundManyLambda<LambdaT>>( ref ) ),
                    m_hint( hint ) {}

                template <typename T,
                          typename = typename std::enable_if_t<
                              !Detail::is_unary_function_v<T>>>
-                ParserRefImpl( T& ref, std::string_view hint ):
+                ParserRefImpl( T& ref, StringRef hint ):
                    m_ref( std::make_shared<BoundValueRef<T>>( ref ) ),
                    m_hint( hint ) {}

                template <typename LambdaT,
                          typename = typename std::enable_if_t<
                              Detail::is_unary_function_v<LambdaT>>>
-                ParserRefImpl( LambdaT const& ref, std::string_view hint ):
+                ParserRefImpl( LambdaT const& ref, StringRef hint ):
                    m_ref( std::make_shared<BoundLambda<LambdaT>>( ref ) ),
                    m_hint( hint ) {}

-                DerivedT& operator()( std::string_view description ) & {
+                DerivedT& operator()( StringRef description ) & {
                    m_description = description;
                    return static_cast<DerivedT&>( *this );
                }
-                DerivedT&& operator()( std::string_view description ) && {
+                DerivedT&& operator()( StringRef description ) && {
                    m_description = description;
                    return static_cast<DerivedT&&>( *this );
                }
@@ -537,7 +547,7 @@ namespace Catch {
                        return 1;
                }

-                std::string_view hint() const { return m_hint; }
+                StringRef hint() const { return m_hint; }
            };

        } // namespace detail
@@ -557,7 +567,7 @@ namespace Catch {
        // A parser for options
        class Opt : public Detail::ParserRefImpl<Opt> {
        protected:
-            std::vector<std::string_view> m_optNames;
+            std::vector<StringRef> m_optNames;

        public:
            template <typename LambdaT>
@@ -570,31 +580,31 @@ namespace Catch {
            template <typename LambdaT,
                      typename = typename std::enable_if_t<
                          Detail::is_unary_function_v<LambdaT>>>
-            Opt( LambdaT const& ref, std::string_view hint ):
+            Opt( LambdaT const& ref, StringRef hint ):
                ParserRefImpl( ref, hint ) {}

            template <typename LambdaT>
-            Opt( accept_many_t, LambdaT const& ref, std::string_view hint ):
+            Opt( accept_many_t, LambdaT const& ref, StringRef hint ):
                ParserRefImpl( accept_many, ref, hint ) {}

            template <typename T,
                      typename = typename std::enable_if_t<
                          !Detail::is_unary_function_v<T>>>
-            Opt( T& ref, std::string_view hint ):
+            Opt( T& ref, StringRef hint ):
                ParserRefImpl( ref, hint ) {}

-            Opt& operator[]( std::string_view optName ) & {
+            Opt& operator[]( StringRef optName ) & {
                m_optNames.push_back(optName);
                return *this;
            }
-            Opt&& operator[]( std::string_view optName ) && {
+            Opt&& operator[]( StringRef optName ) && {
                m_optNames.push_back( optName );
                return CATCH_MOVE(*this);
            }

            Detail::HelpColumns getHelpColumns() const;

-            bool isMatch(std::string_view optToken) const;
+            bool isMatch(StringRef optToken) const;

            using ParserBase::parse;

@@ -695,15 +705,15 @@ namespace Catch {
         */
        class Args {
            friend Detail::TokenStream;
-            std::string_view m_exeName;
-            std::vector<std::string_view> m_args;
+            StringRef m_exeName;
+            std::vector<StringRef> m_args;

        public:
            Args(int argc, char const* const* argv);
            // Helper constructor for testing
-            Args(std::initializer_list<std::string_view> args);
+            Args(std::initializer_list<StringRef> args);

-            std::string_view exeName() const { return m_exeName; }
+            StringRef exeName() const { return m_exeName; }
        };


--- a/src/catch2/internal/catch_commandline.cpp
+++ b/src/catch2/internal/catch_commandline.cpp
@@ -88,7 +88,7 @@ namespace Catch {
                return ParserResult::ok( ParseResultType::Matched );
            };
        auto const setDefaultColourMode = [&]( std::string const& colourMode ) {
-            std::optional<ColourMode> maybeMode = Catch::Detail::stringToColourMode(toLower( colourMode ));
+            Optional<ColourMode> maybeMode = Catch::Detail::stringToColourMode(toLower( colourMode ));
            if ( !maybeMode ) {
                return ParserResult::runtimeError(
                    "colour mode must be one of: default, ansi, win32, "
@@ -135,7 +135,7 @@ namespace Catch {
                return ParserResult::runtimeError( "Received empty reporter spec." );
            }

-            std::optional<ReporterSpec> parsed =
+            Optional<ReporterSpec> parsed =
                parseReporterSpec( userReporterSpec );
            if ( !parsed ) {
                return ParserResult::runtimeError(
@@ -156,7 +156,7 @@ namespace Catch {
            }


-            const bool hadOutputFile = reporterSpec.outputFile().has_value();
+            const bool hadOutputFile = reporterSpec.outputFile().some();
            config.reporterSpecifications.push_back( CATCH_MOVE( *parsed ) );
            // It would be enough to check this only once at the very end, but
            // there is  not a place where we could call this check, so do it
@@ -165,7 +165,7 @@ namespace Catch {
            if (!hadOutputFile) {
                int n_reporters_without_file = 0;
                for (auto const& spec : config.reporterSpecifications) {
-                    if (!spec.outputFile()) {
+                    if (spec.outputFile().none()) {
                        n_reporters_without_file++;
                    }
                }
@@ -305,6 +305,9 @@ namespace Catch {
            | Opt( config.allowZeroTests )
                ["--allow-running-no-tests"]
                ( "Treat 'No tests run' as a success" )
+            | Opt( config.prematureExitGuardFilePath, "path" )
+                ["--premature-exit-guard-file"]
+                ( "create a file before running tests and delete it during clean exit" )
            | Arg( config.testsOrTags, "test name|pattern|tags" )
                ( "which test or tests to use" );

--- a/src/catch2/internal/catch_compiler_capabilities.hpp
+++ b/src/catch2/internal/catch_compiler_capabilities.hpp
@@ -29,6 +29,10 @@

 #ifdef __cplusplus

+#  if (__cplusplus >= 201703L) || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
+#    define CATCH_CPP17_OR_GREATER
+#  endif
+
 #  if (__cplusplus >= 202002L) || (defined(_MSVC_LANG) && _MSVC_LANG >= 202002L)
 #    define CATCH_CPP20_OR_GREATER
 #  endif
@@ -194,7 +198,8 @@
 #   define _BSD_SOURCE
 // some versions of cygwin (most) do not support std::to_string. Use the libstd check.
 // https://gcc.gnu.org/onlinedocs/gcc-4.8.2/libstdc++/api/a01053_source.html line 2812-2813
-# if !(defined(_GLIBCXX_USE_C99) && !defined(_GLIBCXX_HAVE_BROKEN_VSWPRINTF))
+# if !((__cplusplus >= 201103L) && defined(_GLIBCXX_USE_C99) \
+           && !defined(_GLIBCXX_HAVE_BROKEN_VSWPRINTF))

 #    define CATCH_INTERNAL_CONFIG_NO_CPP11_TO_STRING

@@ -270,6 +275,43 @@
 #define CATCH_INTERNAL_CONFIG_GLOBAL_NEXTAFTER
 #endif

+// Various stdlib support checks that require __has_include
+#if defined(__has_include)
+  // Check if string_view is available and usable
+  #if __has_include(<string_view>) && defined(CATCH_CPP17_OR_GREATER)
+  #    define CATCH_INTERNAL_CONFIG_CPP17_STRING_VIEW
+  #endif
+
+  // Check if optional is available and usable
+  #  if __has_include(<optional>) && defined(CATCH_CPP17_OR_GREATER)
+  #    define CATCH_INTERNAL_CONFIG_CPP17_OPTIONAL
+  #  endif // __has_include(<optional>) && defined(CATCH_CPP17_OR_GREATER)
+
+  // Check if byte is available and usable
+  #  if __has_include(<cstddef>) && defined(CATCH_CPP17_OR_GREATER)
+  #    include <cstddef>
+  #    if defined(__cpp_lib_byte) && (__cpp_lib_byte > 0)
+  #      define CATCH_INTERNAL_CONFIG_CPP17_BYTE
+  #    endif
+  #  endif // __has_include(<cstddef>) && defined(CATCH_CPP17_OR_GREATER)
+
+  // Check if variant is available and usable
+  #  if __has_include(<variant>) && defined(CATCH_CPP17_OR_GREATER)
+  #    if defined(__clang__) && (__clang_major__ < 8)
+         // work around clang bug with libstdc++ https://bugs.llvm.org/show_bug.cgi?id=31852
+         // fix should be in clang 8, workaround in libstdc++ 8.2
+  #      include <ciso646>
+  #      if defined(__GLIBCXX__) && defined(_GLIBCXX_RELEASE) && (_GLIBCXX_RELEASE < 9)
+  #        define CATCH_CONFIG_NO_CPP17_VARIANT
+  #      else
+  #        define CATCH_INTERNAL_CONFIG_CPP17_VARIANT
+  #      endif // defined(__GLIBCXX__) && defined(_GLIBCXX_RELEASE) && (_GLIBCXX_RELEASE < 9)
+  #    else
+  #      define CATCH_INTERNAL_CONFIG_CPP17_VARIANT
+  #    endif // defined(__clang__) && (__clang_major__ < 8)
+  #  endif // __has_include(<variant>) && defined(CATCH_CPP17_OR_GREATER)
+#endif // defined(__has_include)
+

 #if defined(CATCH_INTERNAL_CONFIG_WINDOWS_SEH) && !defined(CATCH_CONFIG_NO_WINDOWS_SEH) && !defined(CATCH_CONFIG_WINDOWS_SEH) && !defined(CATCH_INTERNAL_CONFIG_NO_WINDOWS_SEH)
 #   define CATCH_CONFIG_WINDOWS_SEH
@@ -287,6 +329,22 @@
 #    define CATCH_CONFIG_CPP11_TO_STRING
 #endif

+#if defined(CATCH_INTERNAL_CONFIG_CPP17_OPTIONAL) && !defined(CATCH_CONFIG_NO_CPP17_OPTIONAL) && !defined(CATCH_CONFIG_CPP17_OPTIONAL)
+#  define CATCH_CONFIG_CPP17_OPTIONAL
+#endif
+
+#if defined(CATCH_INTERNAL_CONFIG_CPP17_STRING_VIEW) && !defined(CATCH_CONFIG_NO_CPP17_STRING_VIEW) && !defined(CATCH_CONFIG_CPP17_STRING_VIEW)
+#  define CATCH_CONFIG_CPP17_STRING_VIEW
+#endif
+
+#if defined(CATCH_INTERNAL_CONFIG_CPP17_VARIANT) && !defined(CATCH_CONFIG_NO_CPP17_VARIANT) && !defined(CATCH_CONFIG_CPP17_VARIANT)
+#  define CATCH_CONFIG_CPP17_VARIANT
+#endif
+
+#if defined(CATCH_INTERNAL_CONFIG_CPP17_BYTE) && !defined(CATCH_CONFIG_NO_CPP17_BYTE) && !defined(CATCH_CONFIG_CPP17_BYTE)
+#  define CATCH_CONFIG_CPP17_BYTE
+#endif
+

 #if defined(CATCH_CONFIG_EXPERIMENTAL_REDIRECT)
 #  define CATCH_INTERNAL_CONFIG_NEW_CAPTURE
--- a/src/catch2/internal/catch_config_uncaught_exceptions.hpp
+++ b/src/catch2/internal/catch_config_uncaught_exceptions.hpp
@@ -0,0 +1,46 @@
+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+
+/** \file
+ * Wrapper for UNCAUGHT_EXCEPTIONS configuration option
+ *
+ * For some functionality, Catch2 requires to know whether there is
+ * an active exception. Because `std::uncaught_exception` is deprecated
+ * in C++17, we want to use `std::uncaught_exceptions` if possible.
+ */
+
+#ifndef CATCH_CONFIG_UNCAUGHT_EXCEPTIONS_HPP_INCLUDED
+#define CATCH_CONFIG_UNCAUGHT_EXCEPTIONS_HPP_INCLUDED
+
+#include <catch2/catch_user_config.hpp>
+
+#if defined(_MSC_VER)
+#  if _MSC_VER >= 1900 // Visual Studio 2015 or newer
+#    define CATCH_INTERNAL_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS
+#  endif
+#endif
+
+
+#include <exception>
+
+#if defined(__cpp_lib_uncaught_exceptions) \
+    && !defined(CATCH_INTERNAL_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS)
+
+#  define CATCH_INTERNAL_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS
+#endif // __cpp_lib_uncaught_exceptions
+
+
+#if defined(CATCH_INTERNAL_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS) \
+    && !defined(CATCH_CONFIG_NO_CPP17_UNCAUGHT_EXCEPTIONS) \
+    && !defined(CATCH_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS)
+
+#  define CATCH_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS
+#endif
+
+
+#endif // CATCH_CONFIG_UNCAUGHT_EXCEPTIONS_HPP_INCLUDED
--- a/src/catch2/internal/catch_console_colour.cpp
+++ b/src/catch2/internal/catch_console_colour.cpp
@@ -161,7 +161,11 @@ namespace {
 #endif // Windows/ ANSI/ None


-#if defined( CATCH_PLATFORM_LINUX ) || defined( CATCH_PLATFORM_MAC ) || defined( __GLIBC__ ) || defined(__FreeBSD__)
+#if defined( CATCH_PLATFORM_LINUX ) \
+ || defined( CATCH_PLATFORM_MAC ) \
+ || defined( __GLIBC__ ) \
+ || defined( __FreeBSD__ ) \
+ || defined( CATCH_PLATFORM_QNX )
 #    define CATCH_INTERNAL_HAS_ISATTY
 #    include <unistd.h>
 #endif
--- a/src/catch2/internal/catch_container_nonmembers.hpp
+++ b/src/catch2/internal/catch_container_nonmembers.hpp
@@ -0,0 +1,73 @@
+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+#ifndef CATCH_CONTAINER_NONMEMBERS_HPP_INCLUDED
+#define CATCH_CONTAINER_NONMEMBERS_HPP_INCLUDED
+
+#include <catch2/internal/catch_compiler_capabilities.hpp>
+
+#include <cstddef>
+#include <initializer_list>
+
+// We want a simple polyfill over `std::empty`, `std::size` and so on
+// for C++14 or C++ libraries with incomplete support.
+// We also have to handle that MSVC std lib will happily provide these
+// under older standards.
+#if defined(CATCH_CPP17_OR_GREATER) || defined(_MSC_VER)
+
+// We are already using this header either way, so there shouldn't
+// be much additional overhead in including it to get the feature
+// test macros
+#include <string>
+
+#  if !defined(__cpp_lib_nonmember_container_access)
+#      define CATCH_CONFIG_POLYFILL_NONMEMBER_CONTAINER_ACCESS
+#  endif
+
+#else
+#define CATCH_CONFIG_POLYFILL_NONMEMBER_CONTAINER_ACCESS
+#endif
+
+
+
+namespace Catch {
+namespace Detail {
+
+#if defined(CATCH_CONFIG_POLYFILL_NONMEMBER_CONTAINER_ACCESS)
+    template <typename Container>
+    constexpr auto empty(Container const& cont) -> decltype(cont.empty()) {
+        return cont.empty();
+    }
+    template <typename T, std::size_t N>
+    constexpr bool empty(const T (&)[N]) noexcept {
+        // GCC < 7 does not support the const T(&)[] parameter syntax
+        // so we have to ignore the length explicitly
+        (void)N;
+        return false;
+    }
+    template <typename T>
+    constexpr bool empty(std::initializer_list<T> list) noexcept {
+        return list.size() > 0;
+    }
+
+
+    template <typename Container>
+    constexpr auto size(Container const& cont) -> decltype(cont.size()) {
+        return cont.size();
+    }
+    template <typename T, std::size_t N>
+    constexpr std::size_t size(const T(&)[N]) noexcept {
+        return N;
+    }
+#endif // CATCH_CONFIG_POLYFILL_NONMEMBER_CONTAINER_ACCESS
+
+} // end namespace Detail
+} // end namespace Catch
+
+
+
+#endif // CATCH_CONTAINER_NONMEMBERS_HPP_INCLUDED
--- a/src/catch2/internal/catch_debugger.cpp
+++ b/src/catch2/internal/catch_debugger.cpp
@@ -69,7 +69,7 @@
        #endif
    } // namespace Catch

-#elif defined(CATCH_PLATFORM_LINUX)
+#elif defined(CATCH_PLATFORM_LINUX) || defined(CATCH_PLATFORM_QNX)
    #include <fstream>
    #include <string>

--- a/src/catch2/internal/catch_debugger.hpp
+++ b/src/catch2/internal/catch_debugger.hpp
@@ -49,7 +49,7 @@ namespace Catch {
        #define CATCH_TRAP()  __asm__(".inst 0xde01")
    #endif

-#elif defined(CATCH_PLATFORM_LINUX)
+#elif defined(CATCH_PLATFORM_LINUX) || defined(CATCH_PLATFORM_QNX)
    // If we can use inline assembler, do it because this allows us to break
    // directly at the location of the failing check instead of breaking inside
    // raise() called from it, i.e. one stack frame below.
--- a/src/catch2/internal/catch_decomposer.cpp
+++ b/src/catch2/internal/catch_decomposer.cpp
@@ -17,7 +17,7 @@ namespace Catch {
        os << "Some class derived from ITransientExpression without overriding streamReconstructedExpression";
    }

-    void formatReconstructedExpression( std::ostream &os, std::string const& lhs, std::string_view op, std::string const& rhs ) {
+    void formatReconstructedExpression( std::ostream &os, std::string const& lhs, StringRef op, std::string const& rhs ) {
        if( lhs.size() + rhs.size() < 40 &&
                lhs.find('\n') == std::string::npos &&
                rhs.find('\n') == std::string::npos )
--- a/src/catch2/internal/catch_decomposer.hpp
+++ b/src/catch2/internal/catch_decomposer.hpp
@@ -9,8 +9,10 @@
 #define CATCH_DECOMPOSER_HPP_INCLUDED

 #include <catch2/catch_tostring.hpp>
+#include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_compare_traits.hpp>
 #include <catch2/internal/catch_test_failure_exception.hpp>
+#include <catch2/internal/catch_logical_traits.hpp>
 #include <catch2/internal/catch_compiler_capabilities.hpp>

 #include <type_traits>
@@ -127,7 +129,7 @@
 namespace Catch {

    namespace Detail {
-        // This was added in C++20, but we require only C++17 for now.
+        // This was added in C++20, but we require only C++14 for now.
        template <typename T>
        using RemoveCVRef_t = std::remove_cv_t<std::remove_reference_t<T>>;
    }
@@ -146,8 +148,8 @@ namespace Catch {
    template <typename T>
    struct capture_by_value
        : std::integral_constant<bool,
-                                 std::is_arithmetic_v<T> ||
-                                     std::is_enum_v<T>> {};
+                                 std::is_arithmetic<T>::value ||
+                                     std::is_enum<T>::value> {};

 #if defined( CATCH_CONFIG_CPP20_COMPARE_OVERLOADS )
    template <>
@@ -188,12 +190,12 @@ namespace Catch {
        }
    };

-    void formatReconstructedExpression( std::ostream &os, std::string const& lhs, std::string_view op, std::string const& rhs );
+    void formatReconstructedExpression( std::ostream &os, std::string const& lhs, StringRef op, std::string const& rhs );

    template<typename LhsT, typename RhsT>
    class BinaryExpr  : public ITransientExpression {
        LhsT m_lhs;
-        std::string_view m_op;
+        StringRef m_op;
        RhsT m_rhs;

        void streamReconstructedExpression( std::ostream &os ) const override {
@@ -202,7 +204,7 @@ namespace Catch {
        }

    public:
-        constexpr BinaryExpr( bool comparisonResult, LhsT lhs, std::string_view op, RhsT rhs )
+        constexpr BinaryExpr( bool comparisonResult, LhsT lhs, StringRef op, RhsT rhs )
        :   ITransientExpression{ true, comparisonResult },
            m_lhs( lhs ),
            m_op( op ),
@@ -292,48 +294,48 @@ namespace Catch {
    template <typename RhsT>                                                   \
    constexpr friend auto operator op( ExprLhs&& lhs, RhsT&& rhs )             \
        -> std::enable_if_t<                                                   \
-            std::conjunction_v<Detail::is_##id##_comparable<LhsT, RhsT>,       \
-                                std::negation<capture_by_value<                \
-                                    Detail::RemoveCVRef_t<RhsT>>>>,            \
+            Detail::conjunction<Detail::is_##id##_comparable<LhsT, RhsT>,      \
+                                Detail::negation<capture_by_value<             \
+                                    Detail::RemoveCVRef_t<RhsT>>>>::value,     \
            BinaryExpr<LhsT, RhsT const&>> {                                   \
        return {                                                               \
-            static_cast<bool>( lhs.m_lhs op rhs ), lhs.m_lhs, #op, rhs }; \
+            static_cast<bool>( lhs.m_lhs op rhs ), lhs.m_lhs, #op##_sr, rhs }; \
    }                                                                          \
    template <typename RhsT>                                                   \
    constexpr friend auto operator op( ExprLhs&& lhs, RhsT rhs )               \
        -> std::enable_if_t<                                                   \
-            std::conjunction_v<Detail::is_##id##_comparable<LhsT, RhsT>,       \
-                                capture_by_value<RhsT>>,                       \
+            Detail::conjunction<Detail::is_##id##_comparable<LhsT, RhsT>,      \
+                                capture_by_value<RhsT>>::value,                \
            BinaryExpr<LhsT, RhsT>> {                                          \
        return {                                                               \
-            static_cast<bool>( lhs.m_lhs op rhs ), lhs.m_lhs, #op, rhs }; \
+            static_cast<bool>( lhs.m_lhs op rhs ), lhs.m_lhs, #op##_sr, rhs }; \
    }                                                                          \
    template <typename RhsT>                                                   \
    constexpr friend auto operator op( ExprLhs&& lhs, RhsT rhs )               \
        -> std::enable_if_t<                                                   \
-            std::conjunction_v<                                                \
-                std::negation<Detail::is_##id##_comparable<LhsT, RhsT>>,       \
+            Detail::conjunction<                                               \
+                Detail::negation<Detail::is_##id##_comparable<LhsT, RhsT>>,    \
                Detail::is_eq_0_comparable<LhsT>,                              \
              /* We allow long because we want `ptr op NULL` to be accepted */ \
-                std::disjunction<std::is_same<RhsT, int>,                      \
-                                    std::is_same<RhsT, long>>>,                \
+                Detail::disjunction<std::is_same<RhsT, int>,                   \
+                                    std::is_same<RhsT, long>>>::value,         \
            BinaryExpr<LhsT, RhsT>> {                                          \
        if ( rhs != 0 ) { throw_test_failure_exception(); }                    \
        return {                                                               \
-            static_cast<bool>( lhs.m_lhs op 0 ), lhs.m_lhs, #op, rhs };   \
+            static_cast<bool>( lhs.m_lhs op 0 ), lhs.m_lhs, #op##_sr, rhs };   \
    }                                                                          \
    template <typename RhsT>                                                   \
    constexpr friend auto operator op( ExprLhs&& lhs, RhsT rhs )               \
        -> std::enable_if_t<                                                   \
-            std::conjunction_v<                                                \
-                std::negation<Detail::is_##id##_comparable<LhsT, RhsT>>,       \
+            Detail::conjunction<                                               \
+                Detail::negation<Detail::is_##id##_comparable<LhsT, RhsT>>,    \
                Detail::is_eq_0_comparable<RhsT>,                              \
              /* We allow long because we want `ptr op NULL` to be accepted */ \
-                std::disjunction<std::is_same<LhsT, int>,                      \
-                                    std::is_same<LhsT, long>>>,                \
+                Detail::disjunction<std::is_same<LhsT, int>,                   \
+                                    std::is_same<LhsT, long>>>::value,         \
            BinaryExpr<LhsT, RhsT>> {                                          \
        if ( lhs.m_lhs != 0 ) { throw_test_failure_exception(); }              \
-        return { static_cast<bool>( 0 op rhs ), lhs.m_lhs, #op, rhs };    \
+        return { static_cast<bool>( 0 op rhs ), lhs.m_lhs, #op##_sr, rhs };    \
    }

        CATCH_INTERNAL_DEFINE_EXPRESSION_EQUALITY_OPERATOR( eq, == )
@@ -346,44 +348,44 @@ namespace Catch {
    template <typename RhsT>                                                   \
    constexpr friend auto operator op( ExprLhs&& lhs, RhsT&& rhs )             \
        -> std::enable_if_t<                                                   \
-            std::conjunction_v<Detail::is_##id##_comparable<LhsT, RhsT>,       \
-                                std::negation<capture_by_value<                \
-                                    Detail::RemoveCVRef_t<RhsT>>>>,            \
+            Detail::conjunction<Detail::is_##id##_comparable<LhsT, RhsT>,      \
+                                Detail::negation<capture_by_value<             \
+                                    Detail::RemoveCVRef_t<RhsT>>>>::value,     \
            BinaryExpr<LhsT, RhsT const&>> {                                   \
        return {                                                               \
-            static_cast<bool>( lhs.m_lhs op rhs ), lhs.m_lhs, #op, rhs }; \
+            static_cast<bool>( lhs.m_lhs op rhs ), lhs.m_lhs, #op##_sr, rhs }; \
    }                                                                          \
    template <typename RhsT>                                                   \
    constexpr friend auto operator op( ExprLhs&& lhs, RhsT rhs )               \
        -> std::enable_if_t<                                                   \
-            std::conjunction_v<Detail::is_##id##_comparable<LhsT, RhsT>,       \
-                                capture_by_value<RhsT>>      ,                 \
+            Detail::conjunction<Detail::is_##id##_comparable<LhsT, RhsT>,      \
+                                capture_by_value<RhsT>>::value,                \
            BinaryExpr<LhsT, RhsT>> {                                          \
        return {                                                               \
-            static_cast<bool>( lhs.m_lhs op rhs ), lhs.m_lhs, #op, rhs }; \
+            static_cast<bool>( lhs.m_lhs op rhs ), lhs.m_lhs, #op##_sr, rhs }; \
    }                                                                          \
    template <typename RhsT>                                                   \
    constexpr friend auto operator op( ExprLhs&& lhs, RhsT rhs )               \
        -> std::enable_if_t<                                                   \
-            std::conjunction_v<                                                \
-                std::negation<Detail::is_##id##_comparable<LhsT, RhsT>>,       \
+            Detail::conjunction<                                               \
+                Detail::negation<Detail::is_##id##_comparable<LhsT, RhsT>>,    \
                Detail::is_##id##_0_comparable<LhsT>,                          \
-                std::is_same<RhsT, int>>,                                      \
+                std::is_same<RhsT, int>>::value,                               \
            BinaryExpr<LhsT, RhsT>> {                                          \
        if ( rhs != 0 ) { throw_test_failure_exception(); }                    \
        return {                                                               \
-            static_cast<bool>( lhs.m_lhs op 0 ), lhs.m_lhs, #op, rhs };   \
+            static_cast<bool>( lhs.m_lhs op 0 ), lhs.m_lhs, #op##_sr, rhs };   \
    }                                                                          \
    template <typename RhsT>                                                   \
    constexpr friend auto operator op( ExprLhs&& lhs, RhsT rhs )               \
        -> std::enable_if_t<                                                   \
-            std::conjunction_v<                                                \
-                std::negation<Detail::is_##id##_comparable<LhsT, RhsT>>,       \
+            Detail::conjunction<                                               \
+                Detail::negation<Detail::is_##id##_comparable<LhsT, RhsT>>,    \
                Detail::is_##id##_0_comparable<RhsT>,                          \
-                std::is_same<LhsT, int>>,                                      \
+                std::is_same<LhsT, int>>::value,                               \
            BinaryExpr<LhsT, RhsT>> {                                          \
        if ( lhs.m_lhs != 0 ) { throw_test_failure_exception(); }              \
-        return { static_cast<bool>( 0 op rhs ), lhs.m_lhs, #op, rhs };    \
+        return { static_cast<bool>( 0 op rhs ), lhs.m_lhs, #op##_sr, rhs };    \
    }

        CATCH_INTERNAL_DEFINE_EXPRESSION_COMPARISON_OPERATOR( lt, < )
@@ -401,14 +403,14 @@ namespace Catch {
            !capture_by_value<Detail::RemoveCVRef_t<RhsT>>::value,             \
            BinaryExpr<LhsT, RhsT const&>> {                                   \
        return {                                                               \
-            static_cast<bool>( lhs.m_lhs op rhs ), lhs.m_lhs, #op, rhs }; \
+            static_cast<bool>( lhs.m_lhs op rhs ), lhs.m_lhs, #op##_sr, rhs }; \
    }                                                                          \
    template <typename RhsT>                                                   \
    constexpr friend auto operator op( ExprLhs&& lhs, RhsT rhs )               \
        -> std::enable_if_t<capture_by_value<RhsT>::value,                     \
                            BinaryExpr<LhsT, RhsT>> {                          \
        return {                                                               \
-            static_cast<bool>( lhs.m_lhs op rhs ), lhs.m_lhs, #op, rhs }; \
+            static_cast<bool>( lhs.m_lhs op rhs ), lhs.m_lhs, #op##_sr, rhs }; \
    }

        CATCH_INTERNAL_DEFINE_EXPRESSION_OPERATOR(|)
--- a/src/catch2/internal/catch_enum_values_registry.cpp
+++ b/src/catch2/internal/catch_enum_values_registry.cpp
@@ -19,7 +19,7 @@ namespace Catch {
        namespace {
            // Extracts the actual name part of an enum instance
            // In other words, it returns the Blue part of Bikeshed::Colour::Blue
-            std::string_view extractInstanceName(std::string_view enumInstance) {
+            StringRef extractInstanceName(StringRef enumInstance) {
                // Find last occurrence of ":"
                size_t name_start = enumInstance.size();
                while (name_start > 0 && enumInstance[name_start - 1] != ':') {
@@ -29,9 +29,9 @@ namespace Catch {
            }
        }

-        std::vector<std::string_view> parseEnums( std::string_view enums ) {
+        std::vector<StringRef> parseEnums( StringRef enums ) {
            auto enumValues = splitStringRef( enums, ',' );
-            std::vector<std::string_view> parsed;
+            std::vector<StringRef> parsed;
            parsed.reserve( enumValues.size() );
            for( auto const& enumValue : enumValues ) {
                parsed.push_back(trim(extractInstanceName(enumValue)));
@@ -41,15 +41,15 @@ namespace Catch {

        EnumInfo::~EnumInfo() = default;

-        std::string_view EnumInfo::lookup( int value ) const {
+        StringRef EnumInfo::lookup( int value ) const {
            for( auto const& valueToName : m_values ) {
                if( valueToName.first == value )
                    return valueToName.second;
            }
-            return "{** unexpected enum value **}";
+            return "{** unexpected enum value **}"_sr;
        }

-        Catch::Detail::unique_ptr<EnumInfo> makeEnumInfo( std::string_view enumName, std::string_view allValueNames, std::vector<int> const& values ) {
+        Catch::Detail::unique_ptr<EnumInfo> makeEnumInfo( StringRef enumName, StringRef allValueNames, std::vector<int> const& values ) {
            auto enumInfo = Catch::Detail::make_unique<EnumInfo>();
            enumInfo->m_name = enumName;
            enumInfo->m_values.reserve( values.size() );
@@ -63,10 +63,11 @@ namespace Catch {
            return enumInfo;
        }

-        EnumInfo const& EnumValuesRegistry::registerEnum( std::string_view enumName, std::string_view allValueNames, std::vector<int> const& values ) {
+        EnumInfo const& EnumValuesRegistry::registerEnum( StringRef enumName, StringRef allValueNames, std::vector<int> const& values ) {
            m_enumInfos.push_back(makeEnumInfo(enumName, allValueNames, values));
            return *m_enumInfos.back();
        }

    } // Detail
 } // Catch
+
--- a/src/catch2/internal/catch_enum_values_registry.hpp
+++ b/src/catch2/internal/catch_enum_values_registry.hpp
@@ -10,6 +10,7 @@

 #include <catch2/interfaces/catch_interfaces_enum_values_registry.hpp>
 #include <catch2/internal/catch_unique_ptr.hpp>
+#include <catch2/internal/catch_stringref.hpp>

 #include <vector>

@@ -17,16 +18,16 @@ namespace Catch {

    namespace Detail {

-        Catch::Detail::unique_ptr<EnumInfo> makeEnumInfo( std::string_view enumName, std::string_view allValueNames, std::vector<int> const& values );
+        Catch::Detail::unique_ptr<EnumInfo> makeEnumInfo( StringRef enumName, StringRef allValueNames, std::vector<int> const& values );

        class EnumValuesRegistry : public IMutableEnumValuesRegistry {

            std::vector<Catch::Detail::unique_ptr<EnumInfo>> m_enumInfos;

-            EnumInfo const& registerEnum( std::string_view enumName, std::string_view allValueNames, std::vector<int> const& values) override;
+            EnumInfo const& registerEnum( StringRef enumName, StringRef allValueNames, std::vector<int> const& values) override;
        };

-        std::vector<std::string_view> parseEnums( std::string_view enums );
+        std::vector<StringRef> parseEnums( StringRef enums );

    } // Detail

--- a/src/catch2/internal/catch_is_permutation.hpp
+++ b/src/catch2/internal/catch_is_permutation.hpp
@@ -49,7 +49,7 @@ namespace Catch {

        template <typename ForwardIter, typename Sentinel>
        constexpr
-        std::enable_if_t<!std::is_same_v<ForwardIter, Sentinel>,
+        std::enable_if_t<!std::is_same<ForwardIter, Sentinel>::value,
                         std::ptrdiff_t>
        sentinel_distance( ForwardIter iter, const Sentinel sentinel ) {
            std::ptrdiff_t dist = 0;
--- a/src/catch2/internal/catch_jsonwriter.cpp
+++ b/src/catch2/internal/catch_jsonwriter.cpp
@@ -17,21 +17,21 @@ namespace Catch {
                   c == '\n' || c == '\r' || c == '\t';
        }

-        static std::string_view makeEscapeStringRef( char c ) {
+        static Catch::StringRef makeEscapeStringRef( char c ) {
            if ( c == '"' ) {
-                return "\\\"";
+                return "\\\""_sr;
            } else if ( c == '\\' ) {
-                return "\\\\";
+                return "\\\\"_sr;
            } else if ( c == '\b' ) {
-                return "\\b";
+                return "\\b"_sr;
            } else if ( c == '\f' ) {
-                return "\\f";
+                return "\\f"_sr;
            } else if ( c == '\n' ) {
-                return "\\n";
+                return "\\n"_sr;
            } else if ( c == '\r' ) {
-                return "\\r";
+                return "\\r"_sr;
            } else if ( c == '\t' ) {
-                return "\\t";
+                return "\\t"_sr;
            }
            Catch::Detail::Unreachable();
        }
@@ -75,7 +75,7 @@ namespace Catch {
        m_os << '}';
    }

-    JsonValueWriter JsonObjectWriter::write( std::string_view key ) {
+    JsonValueWriter JsonObjectWriter::write( StringRef key ) {
        JsonUtils::appendCommaNewline(
            m_os, m_should_comma, m_indent_level + 1 );

@@ -136,15 +136,15 @@ namespace Catch {
        return JsonArrayWriter{ m_os, m_indent_level };
    }

-    void JsonValueWriter::write( std::string_view value ) && {
+    void JsonValueWriter::write( Catch::StringRef value ) && {
        writeImpl( value, true );
    }

    void JsonValueWriter::write( bool value ) && {
-        writeImpl( value ? "true" : "false", false );
+        writeImpl( value ? "true"_sr : "false"_sr, false );
    }

-    void JsonValueWriter::writeImpl( std::string_view value, bool quote ) {
+    void JsonValueWriter::writeImpl( Catch::StringRef value, bool quote ) {
        if ( quote ) { m_os << '"'; }
        size_t current_start = 0;
        for ( size_t i = 0; i < value.size(); ++i ) {
--- a/src/catch2/internal/catch_jsonwriter.hpp
+++ b/src/catch2/internal/catch_jsonwriter.hpp
@@ -9,6 +9,7 @@
 #define CATCH_JSONWRITER_HPP_INCLUDED

 #include <catch2/internal/catch_reusable_string_stream.hpp>
+#include <catch2/internal/catch_stringref.hpp>

 #include <cstdint>
 #include <sstream>
@@ -34,13 +35,13 @@ namespace Catch {

        template <typename T>
        void write( T const& value ) && {
-            writeImpl( value, !std::is_arithmetic_v<T> );
+            writeImpl( value, !std::is_arithmetic<T>::value );
        }
-        void write( std::string_view value ) &&;
+        void write( StringRef value ) &&;
        void write( bool value ) &&;

    private:
-        void writeImpl( std::string_view value, bool quote );
+        void writeImpl( StringRef value, bool quote );

        // Without this SFINAE, this overload is a better match
        // for `std::string`, `char const*`, `char const[N]` args.
@@ -48,7 +49,7 @@ namespace Catch {
        // and multiple iteration over the strings
        template <typename T,
                  typename = typename std::enable_if_t<
-                      !std::is_convertible_v<T, std::string_view>>>
+                      !std::is_convertible<T, StringRef>::value>>
        void writeImpl( T const& value, bool quote_value ) {
            m_sstream << value;
            writeImpl( m_sstream.str(), quote_value );
@@ -69,7 +70,7 @@ namespace Catch {

        ~JsonObjectWriter();

-        JsonValueWriter write( std::string_view key );
+        JsonValueWriter write( StringRef key );

    private:
        std::ostream& m_os;
--- a/src/catch2/internal/catch_list.cpp
+++ b/src/catch2/internal/catch_list.cpp
@@ -30,7 +30,7 @@ namespace Catch {
            auto const& testSpec = config.testSpec();
            std::vector<TestCaseHandle> matchedTestCases = filterTests(getAllTestCasesSorted(config), testSpec, config);

-            std::map<std::string_view, TagInfo, Detail::CaseInsensitiveLess> tagCounts;
+            std::map<StringRef, TagInfo, Detail::CaseInsensitiveLess> tagCounts;
            for (auto const& testCase : matchedTestCases) {
                for (auto const& tagName : testCase.getTestCaseInfo().tags) {
                    auto it = tagCounts.find(tagName.original);
@@ -75,7 +75,7 @@ namespace Catch {

    } // end anonymous namespace

-    void TagInfo::add( std::string_view spelling ) {
+    void TagInfo::add( StringRef spelling ) {
        ++count;
        spellings.insert( spelling );
    }
--- a/src/catch2/internal/catch_list.hpp
+++ b/src/catch2/internal/catch_list.hpp
@@ -8,9 +8,10 @@
 #ifndef CATCH_LIST_HPP_INCLUDED
 #define CATCH_LIST_HPP_INCLUDED

+#include <catch2/internal/catch_stringref.hpp>
+
 #include <set>
 #include <string>
-#include <string_view>


 namespace Catch {
@@ -23,15 +24,15 @@ namespace Catch {
        std::string name, description;
    };
    struct ListenerDescription {
-        std::string_view name;
+        StringRef name;
        std::string description;
    };

    struct TagInfo {
-        void add(std::string_view spelling);
+        void add(StringRef spelling);
        std::string all() const;

-        std::set<std::string_view> spellings;
+        std::set<StringRef> spellings;
        std::size_t count = 0;
    };

--- a/src/catch2/internal/catch_logical_traits.hpp
+++ b/src/catch2/internal/catch_logical_traits.hpp
@@ -0,0 +1,44 @@
+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+#ifndef CATCH_LOGICAL_TRAITS_HPP_INCLUDED
+#define CATCH_LOGICAL_TRAITS_HPP_INCLUDED
+
+#include <type_traits>
+
+namespace Catch {
+namespace Detail {
+
+#if defined( __cpp_lib_logical_traits ) && __cpp_lib_logical_traits >= 201510
+
+    using std::conjunction;
+    using std::disjunction;
+    using std::negation;
+
+#else
+
+    template <class...> struct conjunction : std::true_type {};
+    template <class B1> struct conjunction<B1> : B1 {};
+    template <class B1, class... Bn>
+    struct conjunction<B1, Bn...>
+        : std::conditional_t<bool( B1::value ), conjunction<Bn...>, B1> {};
+
+    template <class...> struct disjunction : std::false_type {};
+    template <class B1> struct disjunction<B1> : B1 {};
+    template <class B1, class... Bn>
+    struct disjunction<B1, Bn...>
+        : std::conditional_t<bool( B1::value ), B1, disjunction<Bn...>> {};
+
+    template <class B>
+    struct negation : std::integral_constant<bool, !bool(B::value)> {};
+
+#endif
+
+} // namespace Detail
+} // namespace Catch
+
+#endif // CATCH_LOGICAL_TRAITS_HPP_INCLUDED
--- a/src/catch2/internal/catch_message_info.cpp
+++ b/src/catch2/internal/catch_message_info.cpp
@@ -10,7 +10,7 @@

 namespace Catch {

-    MessageInfo::MessageInfo( std::string_view _macroName,
+    MessageInfo::MessageInfo( StringRef _macroName,
                              SourceLineInfo const& _lineInfo,
                              ResultWas::OfType _type )
    :   macroName( _macroName ),
--- a/src/catch2/internal/catch_message_info.hpp
+++ b/src/catch2/internal/catch_message_info.hpp
@@ -11,17 +11,18 @@
 #include <catch2/internal/catch_deprecation_macro.hpp>
 #include <catch2/internal/catch_result_type.hpp>
 #include <catch2/internal/catch_source_line_info.hpp>
+#include <catch2/internal/catch_stringref.hpp>

 #include <string>

 namespace Catch {

    struct MessageInfo {
-        MessageInfo(    std::string_view _macroName,
+        MessageInfo(    StringRef _macroName,
                        SourceLineInfo const& _lineInfo,
                        ResultWas::OfType _type );

-        std::string_view macroName;
+        StringRef macroName;
        std::string message;
        SourceLineInfo lineInfo;
        ResultWas::OfType type;
--- a/src/catch2/internal/catch_meta.hpp
+++ b/src/catch2/internal/catch_meta.hpp
@@ -27,8 +27,16 @@ namespace Catch {
    template <typename Fun, typename... Args>
    struct is_callable<Fun(Args...)> : decltype(is_callable_tester::test<Fun, Args...>(0)) {};

+
+#if defined(__cpp_lib_is_invocable) && __cpp_lib_is_invocable >= 201703
+    // std::result_of is deprecated in C++17 and removed in C++20. Hence, it is
+    // replaced with std::invoke_result here.
    template <typename Func, typename... U>
    using FunctionReturnType = std::remove_reference_t<std::remove_cv_t<std::invoke_result_t<Func, U...>>>;
+#else
+    template <typename Func, typename... U>
+    using FunctionReturnType = std::remove_reference_t<std::remove_cv_t<std::result_of_t<Func(U...)>>>;
+#endif

 } // namespace Catch

--- a/src/catch2/internal/catch_optional.hpp
+++ b/src/catch2/internal/catch_optional.hpp
@@ -0,0 +1,117 @@
+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+#ifndef CATCH_OPTIONAL_HPP_INCLUDED
+#define CATCH_OPTIONAL_HPP_INCLUDED
+
+#include <catch2/internal/catch_move_and_forward.hpp>
+
+#include <cassert>
+
+namespace Catch {
+
+    // An optional type
+    template<typename T>
+    class Optional {
+    public:
+        Optional(): nullableValue( nullptr ) {}
+        ~Optional() { reset(); }
+
+        Optional( T const& _value ):
+            nullableValue( new ( storage ) T( _value ) ) {}
+        Optional( T&& _value ):
+            nullableValue( new ( storage ) T( CATCH_MOVE( _value ) ) ) {}
+
+        Optional& operator=( T const& _value ) {
+            reset();
+            nullableValue = new ( storage ) T( _value );
+            return *this;
+        }
+        Optional& operator=( T&& _value ) {
+            reset();
+            nullableValue = new ( storage ) T( CATCH_MOVE( _value ) );
+            return *this;
+        }
+
+        Optional( Optional const& _other ):
+            nullableValue( _other ? new ( storage ) T( *_other ) : nullptr ) {}
+        Optional( Optional&& _other ):
+            nullableValue( _other ? new ( storage ) T( CATCH_MOVE( *_other ) )
+                                  : nullptr ) {}
+
+        Optional& operator=( Optional const& _other ) {
+            if ( &_other != this ) {
+                reset();
+                if ( _other ) { nullableValue = new ( storage ) T( *_other ); }
+            }
+            return *this;
+        }
+        Optional& operator=( Optional&& _other ) {
+            if ( &_other != this ) {
+                reset();
+                if ( _other ) {
+                    nullableValue = new ( storage ) T( CATCH_MOVE( *_other ) );
+                }
+            }
+            return *this;
+        }
+
+        void reset() {
+            if ( nullableValue ) { nullableValue->~T(); }
+            nullableValue = nullptr;
+        }
+
+        T& operator*() {
+            assert(nullableValue);
+            return *nullableValue;
+        }
+        T const& operator*() const {
+            assert(nullableValue);
+            return *nullableValue;
+        }
+        T* operator->() {
+            assert(nullableValue);
+            return nullableValue;
+        }
+        const T* operator->() const {
+            assert(nullableValue);
+            return nullableValue;
+        }
+
+        T valueOr( T const& defaultValue ) const {
+            return nullableValue ? *nullableValue : defaultValue;
+        }
+
+        bool some() const { return nullableValue != nullptr; }
+        bool none() const { return nullableValue == nullptr; }
+
+        bool operator !() const { return nullableValue == nullptr; }
+        explicit operator bool() const {
+            return some();
+        }
+
+        friend bool operator==(Optional const& a, Optional const& b) {
+            if (a.none() && b.none()) {
+                return true;
+            } else if (a.some() && b.some()) {
+                return *a == *b;
+            } else {
+                return false;
+            }
+        }
+        friend bool operator!=(Optional const& a, Optional const& b) {
+            return !( a == b );
+        }
+
+    private:
+        T* nullableValue;
+        alignas(alignof(T)) char storage[sizeof(T)];
+    };
+
+} // end namespace Catch
+
+#endif // CATCH_OPTIONAL_HPP_INCLUDED
--- a/src/catch2/internal/catch_output_redirect.cpp
+++ b/src/catch2/internal/catch_output_redirect.cpp
@@ -311,6 +311,23 @@ namespace Catch {
        }
    }

+    RedirectGuard::RedirectGuard( RedirectGuard&& rhs ) noexcept:
+        m_redirect( rhs.m_redirect ),
+        m_activate( rhs.m_activate ),
+        m_previouslyActive( rhs.m_previouslyActive ),
+        m_moved( false ) {
+        rhs.m_moved = true;
+    }
+
+    RedirectGuard& RedirectGuard::operator=( RedirectGuard&& rhs ) noexcept {
+        m_redirect = rhs.m_redirect;
+        m_activate = rhs.m_activate;
+        m_previouslyActive = rhs.m_previouslyActive;
+        m_moved = false;
+        rhs.m_moved = true;
+        return *this;
+    }
+
 } // namespace Catch

 #if defined( CATCH_CONFIG_NEW_CAPTURE )
--- a/src/catch2/internal/catch_output_redirect.hpp
+++ b/src/catch2/internal/catch_output_redirect.hpp
@@ -63,6 +63,10 @@ namespace Catch {

        RedirectGuard( RedirectGuard const& ) = delete;
        RedirectGuard& operator=( RedirectGuard const& ) = delete;
+
+        // C++14 needs move-able guards to return them from functions
+        RedirectGuard( RedirectGuard&& rhs ) noexcept;
+        RedirectGuard& operator=( RedirectGuard&& rhs ) noexcept;
    };

    RedirectGuard scopedActivate( OutputRedirect& redirectImpl );
--- a/src/catch2/internal/catch_parse_numbers.cpp
+++ b/src/catch2/internal/catch_parse_numbers.cpp
@@ -12,11 +12,10 @@

 #include <limits>
 #include <stdexcept>
-#include <optional>

 namespace Catch {

-    std::optional<unsigned int> parseUInt(std::string const& input, int base) {
+    Optional<unsigned int> parseUInt(std::string const& input, int base) {
        auto trimmed = trim( input );
        // std::stoull is annoying and accepts numbers starting with '-',
        // it just negates them into unsigned int
--- a/src/catch2/internal/catch_parse_numbers.hpp
+++ b/src/catch2/internal/catch_parse_numbers.hpp
@@ -8,7 +8,8 @@
 #ifndef CATCH_PARSE_NUMBERS_HPP_INCLUDED
 #define CATCH_PARSE_NUMBERS_HPP_INCLUDED

-#include <optional>
+#include <catch2/internal/catch_optional.hpp>
+
 #include <string>

 namespace Catch {
@@ -19,7 +20,7 @@ namespace Catch {
     * Effectively a wrapper around std::stoul but with better error checking
     * e.g. "-1" is rejected, instead of being parsed as UINT_MAX.
     */
-    std::optional<unsigned int> parseUInt(std::string const& input, int base = 10);
+    Optional<unsigned int> parseUInt(std::string const& input, int base = 10);
 }

 #endif // CATCH_PARSE_NUMBERS_HPP_INCLUDED
--- a/src/catch2/internal/catch_platform.hpp
+++ b/src/catch2/internal/catch_platform.hpp
@@ -25,6 +25,9 @@
 #elif defined(linux) || defined(__linux) || defined(__linux__)
 #  define CATCH_PLATFORM_LINUX

+#elif defined(__QNX__)
+#  define CATCH_PLATFORM_QNX
+
 #elif defined(WIN32) || defined(__WIN32__) || defined(_WIN32) || defined(_MSC_VER) || defined(__MINGW32__)
 #  define CATCH_PLATFORM_WINDOWS

--- a/src/catch2/internal/catch_preprocessor.hpp
+++ b/src/catch2/internal/catch_preprocessor.hpp
@@ -176,7 +176,7 @@ namespace Catch {
    template<typename... Ts>\
    void reg_test(TypeList<Ts...>, Catch::NameAndTags nameAndTags)\
    {\
-        Catch::AutoReg( Catch::makeTestInvoker(&TestFunc<Ts...>), CATCH_INTERNAL_LINEINFO, std::string_view(), nameAndTags);\
+        Catch::AutoReg( Catch::makeTestInvoker(&TestFunc<Ts...>), CATCH_INTERNAL_LINEINFO, Catch::StringRef(), nameAndTags);\
    }

 #define INTERNAL_CATCH_NTTP_REGISTER0(TestFunc, signature, ...)
@@ -184,19 +184,19 @@ namespace Catch {
    template<INTERNAL_CATCH_REMOVE_PARENS(signature)>\
    void reg_test(Nttp<__VA_ARGS__>, Catch::NameAndTags nameAndTags)\
    {\
-        Catch::AutoReg( Catch::makeTestInvoker(&TestFunc<__VA_ARGS__>), CATCH_INTERNAL_LINEINFO, std::string_view(), nameAndTags);\
+        Catch::AutoReg( Catch::makeTestInvoker(&TestFunc<__VA_ARGS__>), CATCH_INTERNAL_LINEINFO, Catch::StringRef(), nameAndTags);\
    }

 #define INTERNAL_CATCH_NTTP_REGISTER_METHOD0(TestName, signature, ...)\
    template<typename Type>\
-    void reg_test(TypeList<Type>, std::string_view className, Catch::NameAndTags nameAndTags)\
+    void reg_test(TypeList<Type>, Catch::StringRef className, Catch::NameAndTags nameAndTags)\
    {\
        Catch::AutoReg( Catch::makeTestInvoker(&TestName<Type>::test), CATCH_INTERNAL_LINEINFO, className, nameAndTags);\
    }

 #define INTERNAL_CATCH_NTTP_REGISTER_METHOD(TestName, signature, ...)\
    template<INTERNAL_CATCH_REMOVE_PARENS(signature)>\
-    void reg_test(Nttp<__VA_ARGS__>, std::string_view className, Catch::NameAndTags nameAndTags)\
+    void reg_test(Nttp<__VA_ARGS__>, Catch::StringRef className, Catch::NameAndTags nameAndTags)\
    {\
        Catch::AutoReg( Catch::makeTestInvoker(&TestName<__VA_ARGS__>::test), CATCH_INTERNAL_LINEINFO, className, nameAndTags);\
    }
--- a/src/catch2/internal/catch_preprocessor_internal_stringify.hpp
+++ b/src/catch2/internal/catch_preprocessor_internal_stringify.hpp
@@ -11,9 +11,9 @@
 #include <catch2/catch_user_config.hpp>

 #if !defined(CATCH_CONFIG_DISABLE_STRINGIFICATION)
-  #define CATCH_INTERNAL_STRINGIFY(...) #__VA_ARGS__
+  #define CATCH_INTERNAL_STRINGIFY(...) #__VA_ARGS__##_catch_sr
 #else
-  #define CATCH_INTERNAL_STRINGIFY(...) "Disabled by CATCH_CONFIG_DISABLE_STRINGIFICATION"
+  #define CATCH_INTERNAL_STRINGIFY(...) "Disabled by CATCH_CONFIG_DISABLE_STRINGIFICATION"_catch_sr
 #endif

 #endif // CATCH_PREPROCESSOR_INTERNAL_STRINGIFY_HPP_INCLUDED
--- a/Show More
+++ b/Show More
Author	SHA1	Message	Date
Martin Hořeňovský	b626e4c7ae	Add simple runtime benchmarks For now we add just two binaries, one with assertions taking the fast path, one with assertions taking the slow path, and the ability to run 1 of `REQUIRE(true)`, `REQUIRE_NOTHROW`, `REQUIRE_THROWS` in a loop. I also split off a CMake preset which enables more tests than the basic `simple-tests` preset, but does not enable the most expensive tests which force recompilation of Catch2 multiple times.	2025-09-23 17:17:33 +02:00
Martin Hořeňovský	434bf55d47	Make message push/pop static Since the change to make the message macros thread-safe, and thus thread-local, there is no need to handle messages through instance of `RunContext`.	2025-09-23 11:46:26 +02:00
Martin Hořeňovský	9048c24fa7	Improve QNX support This cherry-picks the source changes from PR made by @pkleymonov-qnx, without including the build path changes that are irrelevant unless we can add a QNX target to our CI. Close #2953	2025-09-22 15:36:46 +02:00
Martin Hořeňovský	8ed8c431c6	Support Bazel's TEST_PREMATURE_EXIT_FILE and add it to CLI as well This tells Catch2 to create an empty file at specified path before the tests start, and delete it after the tests finish. This allows callers to catch cases where the test binary silently exits before finishing (e.g. via call to `exit(0)` inside the code under test), by looking whether the file still exists. Closes #3020	2025-09-22 14:02:45 +02:00