$ 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
