Improve detection of std::uncaught_exceptions support

The problem was that Catch2 did not reliably include `<exception>`
before it checked for the feature test macro for
`std::uncaught_exceptions`. To avoid overhead of including
`<exception>` everywhere, the configuration check was split out
into a separate header.

Closes #2021

include/internal/catch_compiler_capabilities.h

@@ -39,10 +39,6 @@
 
 #endif
 
-#if defined(__cpp_lib_uncaught_exceptions)
-#  define CATCH_INTERNAL_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS
-#endif
-
 // We have to avoid both ICC and Clang, because they try to mask themselves
 // as gcc, and we want only GCC in this block
 #if defined(__GNUC__) && !defined(__clang__) && !defined(__ICC) && !defined(__CUDACC__)
@@ -153,9 +149,6 @@
 #  define CATCH_INTERNAL_START_WARNINGS_SUPPRESSION __pragma( warning(push) )
 #  define CATCH_INTERNAL_STOP_WARNINGS_SUPPRESSION  __pragma( warning(pop) )
 
-#  if _MSC_VER >= 1900 // Visual Studio 2015 or newer
-#    define CATCH_INTERNAL_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS
-#  endif
 
 // Universal Windows platform does not support SEH
 // Or console colours (or console at all...)
@@ -287,10 +280,6 @@
 #  define CATCH_CONFIG_CPP17_OPTIONAL
 #endif
 
-#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
-
 #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

include/internal/catch_config_uncaught_exceptions.hpp

@@ -0,0 +1,44 @@
+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE_1_0.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
+#define CATCH_CONFIG_UNCAUGHT_EXCEPTIONS_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

include/internal/catch_uncaught_exceptions.cpp

@@ -8,6 +8,8 @@
 
 #include "catch_compiler_capabilities.h"
 #include "catch_uncaught_exceptions.h"
+#include "catch_config_uncaught_exceptions.hpp"
+
 #include <exception>
 
 namespace Catch {

projects/CMakeLists.txt

@@ -124,6 +124,7 @@ set(INTERNAL_HEADERS
         ${HEADER_DIR}/internal/catch_common.h
         ${HEADER_DIR}/internal/catch_compiler_capabilities.h
         ${HEADER_DIR}/internal/catch_config.hpp
+        ${HEADER_DIR}/internal/catch_config_uncaught_exceptions.hpp
         ${HEADER_DIR}/internal/catch_console_colour.h
         ${HEADER_DIR}/internal/catch_context.h
         ${HEADER_DIR}/internal/catch_debug_console.h