[clang-cl] Ignore #pragma managed / #pragma unmanaged

[saudi]

Summary

Those 2 pragmas are ignored by MSVC when not compiling with /CLR, which clang doesn't support.
Ignore them in clang -fms-extensions, to avoid -Wunknown-pragma warnings.

See https://learn.microsoft.com/en-us/cpp/preprocessor/managed-unmanaged?view=msvc-170

[thieta]

clang/lib/Lex/Pragma.cpp

1960

I don't see the other comments in this file having "\# I think you can drop that. Also two / for the comments, not three.

[thakis]

LG (except for thieta's nit.)

Do you have commit permissions, or do you need someone to land this for you? If the latter, which name and email should we use for landing it?

[saudi]

In D139632#3985341, @thakis wrote:

LG (except for thieta's nit.)

Do you have commit permissions, or do you need someone to land this for you? If the latter, which name and email should we use for landing it?

I have commit permissions, I can land it myself, thanks!

@thieta The comments formatting I used was copied from similar classes in that same Pragma.cppfile; could you re-check?
e.g. https://github.com/llvm-mirror/clang/blob/master/lib/Lex/Pragma.cpp#L1825

[thieta]

It still looks odd to me, but since the rest of the file has comments like that I am fine with it. But I think we should figure out if they are like that because some tool is parsing them or if it's just legacy.

clang/lib/Lex/Pragma.cpp

void HandlePragma(Preprocessor &PP, PragmaIntroducer Introducer,
                     Token &NameTok) override {
     // #pragma region: endregion matches can be verified
     // __pragma(region): no sense, but ignored by msvc
     // _Pragma is not valid for MSVC, but there isn't any point
     // to handle a _Pragma differently.
   }
 };
 
+/// "\#pragma managed"
+/// "\#pragma managed(...)"
+/// "\#pragma unmanaged"
+/// MSVC ignores this pragma when not compiling using /clr, which clang doesn't
+/// support. We parse it and ignore it to avoid -Wunknown-pragma warnings.
+struct PragmaManagedHandler : public EmptyPragmaHandler {
+  PragmaManagedHandler(const char *pragma) : EmptyPragmaHandler(pragma) {}
+};
+
 /// This handles parsing pragmas that take a macro name and optional message
 static IdentifierInfo *HandleMacroAnnotationPragma(Preprocessor &PP, Token &Tok,
                                                    const char *Pragma,
                                                    std::string &MessageString) {
   PP.Lex(Tok);
   if (Tok.isNot(tok::l_paren)) {
     PP.Diag(Tok, diag::err_expected) << "(";
     return nullptr;
void Preprocessor::RegisterBuiltinPragmas() {
 
   // MS extensions.
   if (LangOpts.MicrosoftExt) {
     AddPragmaHandler(new PragmaWarningHandler());
     AddPragmaHandler(new PragmaExecCharsetHandler());
     AddPragmaHandler(new PragmaIncludeAliasHandler());
     AddPragmaHandler(new PragmaHdrstopHandler());
     AddPragmaHandler(new PragmaSystemHeaderHandler());
+    AddPragmaHandler(new PragmaManagedHandler("managed"));
+    AddPragmaHandler(new PragmaManagedHandler("unmanaged"));
   }
 
   // Pragmas added by plugins
   for (const PragmaHandlerRegistry::entry &handler :
        PragmaHandlerRegistry::entries()) {
     AddPragmaHandler(handler.instantiate().release());
   }
 }

clang/test/Preprocessor/pragma_microsoft.c

 #pragma optimize("g",on)  // expected-warning{{unexpected argument 'g' to '#pragma optimize'; expected ""}}
 #pragma optimize("",on)  // no-warning
 #pragma optimize("", on) asdf // expected-warning{{extra tokens at end of '#pragma optimize'}}
 
 void pragma_optimize_foo() {
 #pragma optimize("", on) // expected-error {{'#pragma optimize' can only appear at file scope}}
 }
 
+#pragma managed            // no-warning
+#pragma unmanaged          // no-warning
+#pragma managed(push, on)  // no-warning
+#pragma managed(pop)       // no-warning
+#pragma managed2           // expected-warning{{unknown pragma ignored}}
+
 #pragma execution_character_set                 // expected-warning {{expected '('}}
 #pragma execution_character_set(                // expected-warning {{expected 'push' or 'pop'}}
 #pragma execution_character_set()               // expected-warning {{expected 'push' or 'pop'}}
 #pragma execution_character_set(asdf            // expected-warning {{expected 'push' or 'pop'}}
 #pragma execution_character_set(asdf)           // expected-warning {{expected 'push' or 'pop'}}
 #pragma execution_character_set(push            // expected-warning {{expected ')'}}
 #pragma execution_character_set(pop,)           // expected-warning {{expected ')'}}
 #pragma execution_character_set(pop,"asdf")     // expected-warning {{expected ')'}}