Re: [PATCH] gimple-ssa-sprintf: Fix typo in range check

[Jakub Jelinek <jakub@redhat.com>]

On Thu, Jul 25, 2024 at 07:48:38PM -0400, Siddhesh Poyarekar wrote:
> The code to scale ranges for wide chars in format_string incorrectly
> checks range.likely to scale range.unlikely, which is a copy-paste typo
> from the immediate previous condition.
> 
> gcc/ChangeLog:
> 
> 	gimple-ssa-sprintf.cc (format_string): Fix type in range check
> 	for UNLIKELY for wide chars.
> 
> Signed-off-by: Siddhesh Poyarekar <siddhesh@gotplt.org>

LGTM.
What exactly the code really wants to do is unclear to me, what does
the INT_MAX on the target have to do with the minimum/maximum/expected
sizes of %S or %ls printed strings is unclear, target PTRDIFF_MAX
maybe.  And why it uses this
	  if (slen.range.something < target_int_max ())
	    slen.range.something *= something_else;
rather than say
	  slen.range.something
	    = MIN (slang.range.something * something_else, target_int_max ());
perhaps with some overflow checking is also something that is hard to guess.
In any case, I think your patch is a step in the right direction.

> --- a/gcc/gimple-ssa-sprintf.cc
> +++ b/gcc/gimple-ssa-sprintf.cc
> @@ -2623,7 +2623,7 @@ format_string (const directive &dir, tree arg, pointer_query &ptr_qry)
>  	  if (slen.range.likely < target_int_max ())
>  	    slen.range.likely *= 2;
>  
> -	  if (slen.range.likely < target_int_max ())
> +	  if (slen.range.unlikely < target_int_max ())
>  	    slen.range.unlikely *= target_mb_len_max ();
>  
>  	  /* A non-empty wide character conversion may fail.  */
> -- 
> 2.45.1

	Jakub