[Bug libgcc/65281] New: Lots of macros using non-reserved names in gthr headers

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65281

            Bug ID: 65281
           Summary: Lots of macros using non-reserved names in gthr
                    headers
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: libgcc
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org

See Bug 64885 comment 6 (referring to libgcc/gthr-single.h and others):

Note the UNUSED macro (whether function-like or not) certainly doesn't belong
to headers included from STL headers either.
It should have been __gthr_unused or something similar.

and Bug 64885 comment 7:

Ditto the header guards like
GCC_GTHR_POSIX_H
GCC_GTHR_SINGLE_H
GCC_GTHR_H
and macros like
GTHREAD_USE_WEAK
HIDE_EXPORTS



This breaks valid programs such as:

#define UNUSED 1
#include <mutex>
int main() { }