[Bug middle-end/109990] [12/13/14 Regression] Bogus -Wuse-after-free warning after realloc

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109990

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> ```
> 
>                   char *new_pool = (char *) realloc (string_space, new_size);
>                   if (new_pool == ((void *)0))
>                     goto out;
>                   if (__builtin_expect (string_space != new_pool, 0))
>                     {
>                       size_t i;
>                       for (i = 0; i < nmap; i++)
>                         {
>                           map[i].alias += new_pool - string_space;
>                           map[i].value += new_pool - string_space;
>                         }
>                     }
>                   string_space = new_pool;
> ```
> 
> Hmmm

Also I think `new_pool - string_space` is undefined really.  That is
subtracting two unrelated arrays is undefined. You can only compare equality on
them.