Cleanup: remove workarounds and version checks for unsupported compilers

Match minimum supported versions from the WIKI [0] by raising them to:

- GCC 9.3.1
- CLANG 8.0
- MVCS 2019 (16.9.16 / 1928)

Details:

- Add CMake checks that ensure supported compiler versions early on.
- Previously GCC per-processor version checks served to exclude
  `__clang__`, in some cases this has been replaced by explicitly
  excluding `__clang__`. This was needed as CLANG treated some of these
  flags differently to GCC, causing the build to fail.
- Remove USE_APPLE_OMP_FIX GCC-4.2 OpenMP workaround.
- Remove linking error workaround for old MSVC versions.

[0]: https://wiki.blender.org/wiki/Building_Blender

Reviewed by: brecht, LazyDodo

Ref D16068

1 files changed, 3 insertions, 7 deletions

diff --git a/source/blender/blenlib/BLI_strict_flags.h b/source/blender/blenlib/BLI_strict_flags.h
index 8489871d5da..cc5b5dce363 100644
--- a/source/blender/blenlib/BLI_strict_flags.h
+++ b/source/blender/blenlib/BLI_strict_flags.h
@@ -9,16 +9,12 @@
  */
 
 #ifdef __GNUC__
-#  if (__GNUC__ * 100 + __GNUC_MINOR__) >= 406 /* gcc4.6+ only */
+/* NOTE(@campbellbarton): CLANG behaves slightly differently to GCC,
+ * these can be enabled but do so carefully as they can introduce build-errors.  */
+#  if !defined(__clang__)
 #    pragma GCC diagnostic error "-Wsign-compare"
-#  endif
-#  if __GNUC__ >= 6 /* gcc6+ only */
 #    pragma GCC diagnostic error "-Wconversion"
-#  endif
-#  if (__GNUC__ * 100 + __GNUC_MINOR__) >= 408
-/* gcc4.8+ only (behavior changed to ignore globals). */
 #    pragma GCC diagnostic error "-Wshadow"
-/* older gcc changed behavior with ternary */
 #    pragma GCC diagnostic error "-Wsign-conversion"
 #  endif
 /* pedantic gives too many issues, developers can define this for own use */