Re: [PATCH 6/6] qemu-io-cmds: Silent GCC9 format-overflow warning

[Richard Henderson]

On 12/17/19 7:34 AM, Philippe Mathieu-Daudé wrote:
> GCC9 is confused when building with CFLAG -O3:
> 
>   In function ‘help_oneline’,
>       inlined from ‘help_all’ at qemu-io-cmds.c:2414:9,
>       inlined from ‘help_f’ at qemu-io-cmds.c:2424:9:
>   qemu-io-cmds.c:2389:9: error: ‘%s’ directive argument is null 
> [-Werror=format-overflow=]
>    2389 |         printf("%s ", ct->name);
>         |         ^~~~~~~~~~~~~~~~~~~~~~~
> 
> Audit shows this can't happen. Give a hint to GCC adding an
> assert() call.

This deserves more investigation.  From my glance it appears you are right --
and moreover impossible for gcc to have come to this conclusion.  Which begs
the question of how that is.

Did you file a gcc bug report?


r~

> 
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> ---
> Cc: Kevin Wolf <address@hidden>
> Cc: Max Reitz <address@hidden>
> Cc: address@hidden
> ---
>  qemu-io-cmds.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
> index 1b7e700020..9e956a5dd4 100644
> --- a/qemu-io-cmds.c
> +++ b/qemu-io-cmds.c
> @@ -2411,6 +2411,7 @@ static void help_all(void)
>      const cmdinfo_t *ct;
>  
>      for (ct = cmdtab; ct < &cmdtab[ncmds]; ct++) {
> +        assert(ct->name);
>          help_oneline(ct->name, ct);
>      }
>      printf("\nUse 'help commandname' for extended help.\n");
>