Only use thread_local in builds with thread safety enabled

MSVC cannot dllexport thread_local variables, so we avoid making
globals thread local if we won't support multiple threads anyway.

Closes #3044

src/CMakeLists.txt

@@ -140,6 +140,7 @@ set(IMPL_HEADERS
   ${SOURCES_DIR}/internal/catch_test_registry.hpp
   ${SOURCES_DIR}/internal/catch_test_spec_parser.hpp
   ${SOURCES_DIR}/internal/catch_textflow.hpp
+  ${SOURCES_DIR}/internal/catch_thread_local.hpp
   ${SOURCES_DIR}/internal/catch_thread_support.hpp
   ${SOURCES_DIR}/internal/catch_to_string.hpp
   ${SOURCES_DIR}/internal/catch_uncaught_exceptions.hpp

src/catch2/catch_all.hpp

@@ -122,6 +122,7 @@
 #include <catch2/internal/catch_test_registry.hpp>
 #include <catch2/internal/catch_test_spec_parser.hpp>
 #include <catch2/internal/catch_textflow.hpp>
+#include <catch2/internal/catch_thread_local.hpp>
 #include <catch2/internal/catch_thread_support.hpp>
 #include <catch2/internal/catch_to_string.hpp>
 #include <catch2/internal/catch_uncaught_exceptions.hpp>

src/catch2/internal/catch_message_info.cpp

@@ -21,6 +21,6 @@ namespace Catch {
 
     // Messages are owned by their individual threads, so the counter should be thread-local as well.
     // Alternative consideration: atomic, so threads don't share IDs and things are easier to debug.
-    thread_local unsigned int MessageInfo::globalCount = 0;
+    CATCH_INTERNAL_THREAD_LOCAL unsigned int MessageInfo::globalCount = 0;
 
 } // end namespace Catch

src/catch2/internal/catch_message_info.hpp

@@ -12,6 +12,7 @@
 #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_thread_local.hpp>
 
 #include <string>
 
@@ -38,7 +39,7 @@ namespace Catch {
             return sequence < other.sequence;
         }
     private:
-        static thread_local unsigned int globalCount;
+        static CATCH_INTERNAL_THREAD_LOCAL unsigned int globalCount;
     };
 
 } // end namespace Catch

src/catch2/internal/catch_run_context.cpp

@@ -20,6 +20,7 @@
 #include <catch2/internal/catch_output_redirect.hpp>
 #include <catch2/internal/catch_assertion_handler.hpp>
 #include <catch2/internal/catch_test_failure_exception.hpp>
+#include <catch2/internal/catch_thread_local.hpp>
 #include <catch2/internal/catch_result_type.hpp>
 
 #include <cassert>
@@ -175,25 +176,25 @@ namespace Catch {
         // from heap, to avoid consuming too much thread-local storage.
 
         // This is used for the "if" part of CHECKED_IF/CHECKED_ELSE
-        static thread_local bool g_lastAssertionPassed = false;
+        static CATCH_INTERNAL_THREAD_LOCAL bool g_lastAssertionPassed = false;
 
         // This is the source location for last encountered macro. It is
         // used to provide the users with more precise location of error
         // when an unexpected exception/fatal error happens.
-        static thread_local SourceLineInfo g_lastKnownLineInfo("DummyLocation", static_cast<size_t>(-1));
+        static CATCH_INTERNAL_THREAD_LOCAL SourceLineInfo g_lastKnownLineInfo("DummyLocation", static_cast<size_t>(-1));
 
         // Should we clear message scopes before sending off the messages to
         // reporter? Set in `assertionPassedFastPath` to avoid doing the full
         // clear there for performance reasons.
-        static thread_local bool g_clearMessageScopes = false;
+        static CATCH_INTERNAL_THREAD_LOCAL bool g_clearMessageScopes = false;
 
         CATCH_INTERNAL_START_WARNINGS_SUPPRESSION
         CATCH_INTERNAL_SUPPRESS_GLOBALS_WARNINGS
         // Actual messages to be provided to the reporter
-        static thread_local std::vector<MessageInfo> g_messages;
+        static CATCH_INTERNAL_THREAD_LOCAL std::vector<MessageInfo> g_messages;
 
         // Owners for the UNSCOPED_X information macro
-        static thread_local std::vector<ScopedMessage> g_messageScopes;
+        static CATCH_INTERNAL_THREAD_LOCAL std::vector<ScopedMessage> g_messageScopes;
         CATCH_INTERNAL_STOP_WARNINGS_SUPPRESSION
 
     } // namespace Detail

src/catch2/internal/catch_thread_local.hpp

@@ -0,0 +1,19 @@
+
+//              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_THREAD_LOCAL_HPP_INCLUDED
+#define CATCH_THREAD_LOCAL_HPP_INCLUDED
+
+#include <catch2/catch_user_config.hpp>
+
+#if defined( CATCH_CONFIG_EXPERIMENTAL_THREAD_SAFE_ASSERTIONS )
+#define CATCH_INTERNAL_THREAD_LOCAL thread_local
+#else
+#define CATCH_INTERNAL_THREAD_LOCAL
+#endif
+
+#endif // CATCH_THREAD_LOCAL_HPP_INCLUDED

src/catch2/meson.build

@@ -148,6 +148,7 @@ internal_headers = [
   'internal/catch_test_registry.hpp',
   'internal/catch_test_spec_parser.hpp',
   'internal/catch_textflow.hpp',
+  'internal/catch_thread_local.hpp',
   'internal/catch_thread_support.hpp',
   'internal/catch_to_string.hpp',
   'internal/catch_uncaught_exceptions.hpp',