Re: [musl] [PATCH 1/1] reallocarray casting overflow check explicitally

[Szabolcs Nagy <nsz@port70.net>]

* David CARLIER <devnexen@gmail.com> [2021-05-10 20:48:26 +0100]:
> From 04e3caa580cfe501ad00d85d63040de329962823 Mon Sep 17 00:00:00 2001
> From: David Carlier <devnexen@gmail.com>
> Date: Mon, 10 May 2021 20:45:12 +0100
> Subject: [PATCH] reallocarray overflow check cast to size_t
> 
> ---
>  src/malloc/reallocarray.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/src/malloc/reallocarray.c b/src/malloc/reallocarray.c
> index 4a6ebe46..2556c917 100644
> --- a/src/malloc/reallocarray.c
> +++ b/src/malloc/reallocarray.c
> @@ -4,7 +4,7 @@
>  
>  void *reallocarray(void *ptr, size_t m, size_t n)
>  {
> -	if (n && m > -1 / n) {
> +	if (n && m > (size_t)-1 / n) {

you need to explain this change more i think.

the usual arithmetic conversion rules of c already convert both
operands of / to size_t, unless size_t has lower conversion rank
than signed int, but such a system would have problems because
size_t was always promoted to int so you would need a lot more
casts in musl (and other software) to avoid signed int overflow
and negative arithmetics.

>  		errno = ENOMEM;
>  		return 0;
>  	}
> -- 
> 2.20.1
>