Re: [PATCH] meson: -Wno-error=format-overflow for ubsan

[Philippe Mathieu-Daudé]

Hi Akihiko,

On 20/11/23 12:23, Akihiko Odaki wrote:
> ubsan causes wrong -Wformat-overflow warnings as follows:
>
> In file included from /usr/include/stdio.h:906,
>                   from /home/alarm/q/var/qemu/include/qemu/osdep.h:114,
>                   from ../disas/cris.c:21:
> In function 'sprintf',
>      inlined from 'format_dec' at ../disas/cris.c:1737:3,
>      inlined from 'print_with_operands' at ../disas/cris.c:2477:12,
>      inlined from 'print_insn_cris_generic.constprop' at ../disas/cris.c:2690:8:
> /usr/include/bits/stdio2.h:30:10: warning: null destination pointer 
> [-Wformat-overflow=]
>     30 |   return __builtin___sprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
>        |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>     31 |                                   __glibc_objsize (__s), __fmt,
>        |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>     32 |                                   __va_arg_pack ());
>        |                                   ~~~~~~~~~~~~~~~~~
>
> Don't let these errors stop the build.

Which compiler/version?

> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> ---
>   meson.build | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/meson.build b/meson.build
> index d7d841e71e..02f1a18080 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -365,7 +365,9 @@ if get_option('sanitizers')
>     # Detect static linking issue with ubsan - 
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84285
>     if cc.links('int main(int argc, char **argv) { return argc + 1; }',
>                 args: [qemu_ldflags, '-fsanitize=undefined'])
> -    qemu_cflags = ['-fsanitize=undefined'] + qemu_cflags
> +    # 87884 – ubsan causes wrong -Wformat-overflow warning
> +    # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87884
> +    qemu_cflags = ['-fsanitize=undefined', '-Wno-error=format-overflow'] + 
> qemu_cflags
>       qemu_ldflags = ['-fsanitize=undefined'] + qemu_ldflags
>     endif
>   endif