[Bug preprocessor/36279] New: division by zero in #if

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

$ cat argh.h 
#define __x(y) __NR_##y
#define x(y) __x(y)
/* define HAVE_FOO if __NR_XXX is defined: */
#define __NR_read 0
#undef __NR_write
#ifdef BUG2
#define __NR_ac%scess 1
#endif

#if defined XXX
# if x(XXX) >= 0
#  define HAVE_FOO 1
#  warning HAVE_FOO
# else
#  undef HAVE_FOO
#  warning no FOO
# endif
#endif

$ echo | gcc-4.4-trunk -DXXX=acce%ss -include argh.h -c - -E -P
In file included from <command-line>:0:
./argh.h:11:13: error: division by zero in #if
./argh.h:13:4: warning: #warning HAVE_FOO



Another (alleged) one, BUG2:
$ echo | gcc-4.4-trunk -DBUG2 -DXXX=read -include argh.h -c - -E -P
In file included from <command-line>:0:
./argh.h:7:16: warning: missing whitespace after the macro name
./argh.h:13:4: warning: #warning HAVE_FOO


And something that would be handy to have but that doesn't seem to work for me:
This is Ok, __NR_read is defined:
$ echo | gcc-4.4-trunk -DXXX=read -include argh.h -c - -E -P
In file included from <command-line>:0:
./argh.h:13:4: warning: #warning HAVE_FOO

This is not OK, i'd expect this to be "no FOO" since __NR_write is *not*
defined:
$ echo | gcc-4.4-trunk -DXXX=write -include argh.h -c - -E -P
In file included from <command-line>:0:
./argh.h:13:4: warning: #warning HAVE_FOO


-- 
           Summary: division by zero in #if
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: aldot at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36279