[Bug preprocessor/48192] New: Conditional macros should not pass #ifdef

["meissner at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48192

           Summary: Conditional macros should not pass #ifdef
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
        AssignedTo: meissner@gcc.gnu.org
        ReportedBy: meissner@gcc.gnu.org
              Host: powerpc64-linux
            Target: powerpc64-linux
             Build: powerpc64-linux


The PowerPC port defines 3 conditional macros, vector, bool, and pixel in
non-standards complaint mode to implement the Altivec/VSX vector keywords.  The
rs6000 backend only expands these keywords if the next token is a type or
keyword that would be used for the Altivec/VSX vector support, to allow the
user to use these 'keywords' as normal identifiers.  So vector int foo; would
expand vector to the vector __attribute__ to define a vector type, but int
vector = 0 would not be expanded.

The Spu also defines vector as a conditional macro.

No other port currently uses conditional macros.

The problem is if the user does:
#ifndef bool
#define bool char
#endif
static bool variable = 0;

The #ifndef case will not succeed because 'bool' is a macro, but 'bool' will
not be expanded because it was not preceded with 'vector'.