Re: [PATCH] fix printf positional arguments for !_MB_CAPABLE case

[Corinna Vinschen <vinschen at redhat dot com>]

On Jan  9 14:50, Ivan Grokhotkov wrote:
> Hi,
> In newlib builds with multibyte support disabled and positional arguments support enabled, positional arguments sometimes are not printed correctly. For example,
> 
>     printf(“%1$f”, 1.0);
> 
> may print garbage value on a 32-bit platform.
> 
> This issue happens because the code path in get_arg, which looks for ‘%’ character, does not work correctly for the ! _MB_CAPABLE case. In _MB_CAPABLE case, fmt pointer is advanced to the next character, and then the check for ‘%’ is performed. In !_MB_CAPABLE case, the check is performed before advancing ‘fmt’ pointer. Net result is that in !_MB_CAPABLE case fmt still points to ‘%’ character, which causes the subsequent state machine to go from START to DONE state immediately. ‘spec_type’ defaults to INT, so arguments which are longer than int (for example, double) are not fetched correctly using va_arg.
> 
> Patch is attached.
> 
> Thanks,
> Ivan

Pushed.


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat

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