[Bug middle-end/84831] Invalid memory read in parse_output_constraint

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84831

--- Comment #5 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Jakub Jelinek from comment #4)
> diff -upbd of that for better readability.
> 
> --- gcc/stmt.c.jj	2018-01-03 10:19:55.150533956 +0100
> +++ gcc/stmt.c	2018-03-12 13:25:03.790733765 +0100
> @@ -247,7 +247,8 @@ parse_output_constraint (const char **co
>      }
>  
>    /* Loop through the constraint string.  */
> -  for (p = constraint + 1; *p; p += CONSTRAINT_LEN (*p, p))
> +  for (p = constraint + 1; *p; )
> +    {
>      switch (*p)
>        {
>        case '+':
> @@ -304,6 +305,11 @@ parse_output_constraint (const char **co
>  	break;
>        }
>  
> +      for (size_t len = CONSTRAINT_LEN (*p, p); len; len--, p++)
> +	if (*p == '\0')
> +	  break;
> +    }
> +
>    return true;
>  }
>  
> 

Both patches should work.  I have no preference.  Thanks.