https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106267
Bug ID: 106267
Summary: #pragma GCC diagnostic ignored not preserved for a
-Wattribute-alias warning
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: preprocessor
Assignee: unassigned at gcc dot gnu.org
Reporter: marxin at gcc dot gnu.org
Target Milestone: ---
For the following code snippet isolated from Linux kernel the ignored
-Wattribute-alias is not preserved:
$ cat posix-stubs.c
#define __diag_GCC(version, severity, s)
\
__diag_GCC_##version(__diag_GCC_##severity s)
#define __diag_GCC_ignore ignored
#define __diag_str1(s) #s
#define __diag_str(s) __diag_str1(s)
#define __diag(s) _Pragma(__diag_str(GCC diagnostic s))
#define __diag_GCC_8(s) __diag(s)
#define __diag_pop() __diag(pop)
#define __diag_push() __diag(push)
#define __diag_ignore(compiler, version, option, comment)
\
__diag_##compiler(version, ignore, option)
#define SYSCALL_ALIAS_PROTO(a) \
__diag_push(); \
__diag_ignore(GCC, 8, "-Wattribute-alias", \
"Alias to nonimplemented syscall"); \
typeof(a) a __attribute__((alias("sys_ni_posix_timers"))); \
__diag_pop()
int sys_timer_create(int);
void sys_ni_posix_timers(void) {}
#define SYS_NI(name) SYSCALL_ALIAS_PROTO(sys_##name)
SYS_NI(timer_create)
$ gcc posix-stubs.c -c -Werror
posix-stubs.c:23:42: error: ‘sys_timer_create’ alias between functions of
incompatible types ‘int(int)’ and ‘void(void)’ [-Werror=attribute-alias=]
23 | #define SYS_NI(name) SYSCALL_ALIAS_PROTO(sys_##name)
| ^~~~
posix-stubs.c:17:19: note: in definition of macro ‘SYSCALL_ALIAS_PROTO’
17 | typeof(a) a __attribute__((alias("sys_ni_posix_timers"))); \
| ^
posix-stubs.c:24:1: note: in expansion of macro ‘SYS_NI’
24 | SYS_NI(timer_create)
| ^~~~~~
posix-stubs.c:21:6: note: aliased declaration here
21 | void sys_ni_posix_timers(void) {}
| ^~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
While using pre-processed input works correctly:
$ gcc posix-stubs.c -c -Werror -E > posix-stubs.i && gcc posix-stubs.i -c
-Werror
