[MS Bugs] char/signed char decl compatibility.

[Bigcheese]

Bugzilla Link	8888
Resolution	FIXED
Resolved on	Jul 26, 2014 14:16
Version	trunk
OS	All
Blocks	llvm/llvm-bugzilla-archive#13707
CC	@AaronBallman,@tritao,@nico

Extended Description

MSVC allows the following in C mode (in C++ it's always legal because of overloading) while clang (correctly) does not. Clang should support this in ms-extensions mode, although I do not yet know the exact semantics (does it use signed or unsigned?).

int __cdecl _access( const char * _Filename, int _AccessMode);
int __cdecl _access( const signed char *path,int amode)
{
return 0;
}

C:\Users\Michael\Projects\msvcrt\research>clang -fsyntax-only double-decl.c
double-decl.c(2) : error: conflicting types for '_access'
int __cdecl _access( const signed char *path,int amode)
^
double-decl.c(1) : note: previous declaration is here
int __cdecl _access( const char * _Filename, int _AccessMode);
^
1 error generated.

C:\Users\Michael\Projects\msvcrt\research>clang++ -fsyntax-only -x c++ double-decl.c

C:\Users\Michael\Projects\msvcrt\research>cl -Zs double-decl.c -nologo

[AaronBallman]

The semantics depend on the presence of the /J switch.

http://msdn.microsoft.com/en-us/library/0d294k5z.aspx

By default (without /J), char is signed. With /J, it sets _CHAR_UNSIGNED and char defaults to unsigned.

[nico]

Looks like we fixed this:

Nicos-MacBook-Pro:llvm-rw thakis$ cat test.cc
int __cdecl _access( const char * _Filename, int _AccessMode);
int __cdecl _access( const signed char *path,int amode)
{
return 0;
}
Nicos-MacBook-Pro:llvm-rw thakis$ ../llvm-build/bin/clang-cl /c test.cc

(clang-cl supports /J too.)