Always allow "#pragma region".

[mattd]

Summary

Both MS and PS4 targets are capable of recognizing the
existence of: #pragma region, #pragma endregion.

Since this pragma is only a hint for certain editors, and has no logic,
it seems helpful to permit this pragma in all cases, not just MS compatibility mode.

[majnemer]

Why not always support the pragma regardless of the compiler mode? Our "support" for it just ignores it anyway...

[mattd]

In D42248#980541, @majnemer wrote:

Why not always support the pragma regardless of the compiler mode? Our "support" for it just ignores it anyway...

Thanks for the reply @majnemer.

I am not opposed to that idea. My change just operates similar to the existing behavior. The only reservation I had against not always accepting the pragma is that it might mislead devs who are not using PS4/VS based environments.

[probinson]

Well, my understanding is that the pragma is a complete no-op even for MSVC, and is used only as a marker for editors such as Visual Studio's.
So, unconditionally ignoring it would seem to be fine.

[mattd]

I'm certainly fine with always allowing this pragma. I can see it useful for other editors that might wish to utilize the hint.

[mattd]

Ping.

[• Quuxplusone]

FWIW, I would also like this patch, because it would mean that I could build with -Werror even when the project includes headers written by MSVC-using people. Given that we know what "#pragma region" does, it hardly deserves an "unknown pragma" diagnostic! So this patch is great IMHO. :)

[majnemer]

LGTM

[mattd]

Thanks @majnemer! Would you mind committing this on my behalf? I do not have commit access, thanks.

lib/Lex/Pragma.cpp

void Preprocessor::RegisterBuiltinPragmas() {
   // #pragma clang module ...
   auto *ModuleHandler = new PragmaNamespace("module");
   AddPragmaHandler("clang", ModuleHandler);
   ModuleHandler->AddPragma(new PragmaModuleImportHandler());
   ModuleHandler->AddPragma(new PragmaModuleBeginHandler());
   ModuleHandler->AddPragma(new PragmaModuleEndHandler());
   ModuleHandler->AddPragma(new PragmaModuleBuildHandler());
   ModuleHandler->AddPragma(new PragmaModuleLoadHandler());
     
+  // Add region pragmas.
+  AddPragmaHandler(new PragmaRegionHandler("region"));
+  AddPragmaHandler(new PragmaRegionHandler("endregion"));
+
   // MS extensions.
   if (LangOpts.MicrosoftExt) {
     AddPragmaHandler(new PragmaWarningHandler());
     AddPragmaHandler(new PragmaIncludeAliasHandler());
-    AddPragmaHandler(new PragmaRegionHandler("region"));
-    AddPragmaHandler(new PragmaRegionHandler("endregion"));
   }
 
   // Pragmas added by plugins
   for (PragmaHandlerRegistry::iterator it = PragmaHandlerRegistry::begin(),
                                        ie = PragmaHandlerRegistry::end();
        it != ie; ++it) {
     AddPragmaHandler(it->instantiate().release());
   }

test/Frontend/region-pragmas.c

+// RUN: %clang_cc1 -Wall -verify %s
+// expected-no-diagnostics
+
+#pragma region foo
+#pragma endregion foo