clang-cl: support __cdecl-on-struct anachronism

[sberg]

Summary

The Microsoft compiler emits

warning C4229: anachronism used : modifiers on data are ignored

for

struct {} __cdecl s;

but ICU's gendict can generate such (and does when building LibreOffice), so accepting this in clang-cl too would be useful.

[rnk]

lib/Parse/ParseDeclCXX.cpp

1108–1110

I think this would be clearer as:

// We will diagnose __cdecl on non-function declarations later, so claim that is valid
// after a type specifier.
return getLangOpts().MicrosoftExt;

Unpacking what the fallthrough does is a little tricky.

[majnemer]

lib/Parse/ParseDeclCXX.cpp

1107

What about __fastcall, etc.

[sberg]

lib/Parse/ParseDeclCXX.cpp

1107

To be honest, I have no idea what the full set of keywords is that would need to be taken care of here (so hoped I would get away with just the one I happened to come across ;)

[majnemer]

lib/Parse/ParseDeclCXX.cpp

1107

The complete list is https://msdn.microsoft.com/en-us/library/984x0h58.aspx#mainBody

[sberg]

updated as discussed in the comments

[sberg]

friendly ping

[rnk]

Thanks, lgtm.

[sberg]

Can you please push this, I do not have commit access. Thanks

[sberg]

friendly ping

lib/Parse/ParseDeclCXX.cpp

bool Parser::isValidAfterTypeSpecifier(bool CouldBeBitfield) {
   case tok::l_square:           // void f(struct f  [         3])
   case tok::ellipsis:           // void f(struct f  ...       [Ns])
   // FIXME: we should emit semantic diagnostic when declaration
   // attribute is in type attribute position.
   case tok::kw___attribute:     // struct foo __attribute__((used)) x;
     return true;
   case tok::colon:
     return CouldBeBitfield;     // enum E { ... }   :         2;
+  // Microsoft compatibility
+  case tok::kw___cdecl:         // struct foo {...} __cdecl   x; // C4229
+    if (!getLangOpts().MicrosoftExt)
+      break;
+    // fall through
   // Type qualifiers
   case tok::kw_const:           // struct foo {...} const     x;
   case tok::kw_volatile:        // struct foo {...} volatile  x;
   case tok::kw_restrict:        // struct foo {...} restrict  x;
   case tok::kw__Atomic:         // struct foo {...} _Atomic   x;
   case tok::kw___unaligned:     // struct foo {...} __unaligned *x;
   // Function specifiers
   // Note, no 'explicit'. An explicit function must be either a conversion

test/Parser/ms-anachronism.c

+// RUN: %clang_cc1 -triple i686-windows-msvc -fms-extensions -fsyntax-only -verify %s
+
+struct {} __cdecl s; // expected-warning {{'__cdecl' only applies to function types; type here is 'struct}}