[PATCH] CodeGen: __uuidof should work even with an incomplete _GUID type

[David Majnemer]

================
Comment at: test/CodeGenCXX/microsoft-uuidof.cpp:8
@@ +7,3 @@
+#ifdef WRONG_GUID
+    unsigned int SomethingWentWrong[4];
+#else
----------------
Reid Kleckner wrote:
> I was expecting a diagnostic.  :)
> 
> Previously clang would reject this code:
> struct __declspec(uuid("12345678-1234-1234-1234-1234567890aB")) S { };
> typedef struct _GUID { int x; int y; } GUID;
> GUID g = __uuidof(S);
> 
> cl.exe accepts and only copies the first 8 bytes, but I'd like to preserve the original clang behavior.  Can we at least check that the sizeof() the user's type is 16?
Are we going into the business of making sure system-types are well formed? It isn't really a user type, it starts with an underscore and a capital letter... We don't make sure the std::type_info type is proper.

That said, consider it done if you guys feel strongly about it.

================
Comment at: lib/CodeGen/CodeGenModule.cpp:1063
@@ -1074,3 +1062,3 @@
       /*isConstant=*/true, llvm::GlobalValue::ExternalLinkage, Init, Name);
   GV->setUnnamedAddr(true);
   return GV;
----------------
Richard Smith wrote:
> Is unnamed_addr really correct for these things?
That was there when I got here. ;)

LangRef makes it sound like appropriate for this case:
> Global variables can be marked with unnamed_addr which indicates that the address is not significant, only the content. Constants marked like this can be merged with other constants if they have the same initializer. Note that a constant with significant address can be merged with a unnamed_addr constant, the result being a constant whose address is significant."

What was your thinking?


http://llvm-reviews.chandlerc.com/D1375