[Mod] libopenmpt: Deprecate the use of mingw-std-threads. See <https:…

…//forum.openmpt.org/index.php?topic=6822>, <meganz/mingw-std-threads#79> and <gcc-mirror/gcc@b204d77>.

git-svn-id: https://source.openmpt.org/svn/openmpt/trunk/OpenMPT@17363 56274372-70c3-4bfc-bfc3-4c3a0b034d27

libopenmpt/dox/changelog.md

@@ -70,6 +70,9 @@ is just a high-level summary.
     defaults to `1` and implies building a liballegro42 locally. This requires
     executing `build/download_externals.sh` before building to download the
     liballegro42 sources.
+ *  [**Change**] Support for mingw-std-threads when building for MinGW targets
+    is now deprecated because this is not supported for GCC 11 or later (see
+    <https://github.com/meganz/mingw-std-threads/issues/79>).
 
  *  [**Regression**] Full support for Visual Studio 2017 has been removed. We
     still support targeting Windows XP with Visual Studio 2017.

libopenmpt/dox/dependencies.md

@@ -24,8 +24,7 @@ Dependencies
      *  **GCC 8.1** or higher
      *  **Clang 7** or higher
      *  **MinGW-W64 8.1** or higher (it is recommended to preferably use
-        posix threading model as opposed to win32 threading model, or at least
-        have mingw-std-threads available otherwise)
+        posix threading model as opposed to win32 threading model)
      *  **emscripten 3.1.1** or higher
      *  **DJGPP GCC 8.1** or higher
      *  any other **C++17 compliant** compiler

libopenmpt/libopenmpt_impl.cpp

@@ -87,8 +87,12 @@ MPT_WARNING("Warning: libopenmpt for WinRT is built with reduced functionality.
 MPT_WARNING("Warning: libopenmpt built in non thread-safe mode because mutexes are not supported by the C++ standard library available.")
 #endif // MPT_MUTEX_NONE
 
-#if (defined(__MINGW32__) || defined(__MINGW64__)) && !defined(_GLIBCXX_HAS_GTHREADS) && !defined(MPT_WITH_MINGWSTDTHREADS)
-MPT_WARNING("Warning: Building libopenmpt with MinGW-w64 without std::thread support is not recommended and is deprecated. Please use MinGW-w64 with posix threading model (as opposed to win32 threading model), or build with mingw-std-threads.")
+#if (defined(__MINGW32__) || defined(__MINGW64__)) && !defined(_GLIBCXX_HAS_GTHREADS) 
+#if defined(MPT_WITH_MINGWSTDTHREADS)
+MPT_WARNING("Warning: Building with mingw-std-threads is deprecated because this is not supported with GCC 11 or later.")
+#else // !MINGWSTDTHREADS
+MPT_WARNING("Warning: Building libopenmpt with MinGW-w64 without std::thread support is not recommended and is deprecated. Please use MinGW-w64 with posix threading model (as opposed to win32 threading model).")
+#enduf // MINGWSTDTHREADS
 #endif // MINGW
 
 #if MPT_CLANG_AT_LEAST(5,0,0) && MPT_CLANG_BEFORE(11,0,0) && defined(__powerpc__) && !defined(__powerpc64__)