Re: Strange code in emacs.c

[Paul Eggert <eggert@cs.ucla.edu>]

Eli Zaretskii wrote:
> We have this in 'main':
> 
>        emacs_re_safe_alloca = max
>          (min (lim - extra, SIZE_MAX) * (min_ratio / ratio),
>           MAX_ALLOCA);
> 
> This always yields MAX_ALLOCA because 'ratio' is always greater than
> 'min_ratio':
> 
>        int min_ratio = 20 * sizeof (char *);
>        int ratio = min_ratio + min_ratio / 3;
> 
> Don't we mean to set emacs_re_safe_alloca like this instead:
> 
>        emacs_re_safe_alloca = min (lim - extra, SIZE_MAX) / ratio;
>        emacs_re_safe_alloca = max (emacs_re_safe_alloca * min_ratio, MAX_ALLOCA);

Yes, that sounds better to me too. Also, that SIZE_MAX should be changed to min 
(SIZE_MAX, PTRDIFF_MAX) to avoid (unlikely) integer-overflow issues.

Should this fix be put into master or into the emacs-26 branch?