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Date: Tue, 13 Jul 2021 11:49:35 -0300
From: √Črico Nogueira <ericonr@...root.org>
To: <musl@...ts.openwall.com>
Subject: Re: Changes for strcspn(), strspn(), strtok() and strtok_r()

On Tue Jul 13, 2021 at 9:02 AM -03, Stefan Kanthak wrote:
> <https://git.musl-libc.org/cgit/musl/plain/src/string/strcspn.c>
>
> #include <string.h>
>  
> #define BITOP(a,b,op) \
> ((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof
> *(a))))
>  
> -size_t strcspn(const char *s, const char *c)
> +size_t strcspn(const char *restrict s, const char *c)
> {
> - const char *a = s;
> + const char *a;
> - size_t byteset[32/sizeof(size_t)];
> + size_t byteset[32/sizeof(size_t)] = { 0 };
>  
> - if (!c[0] || !c[1]) return __strchrnul(s, *c)-a;
> + if (!c[0] || !c[1]) return __strchrnul(a=s, *c)-a;

This is unspecified behavior and could lead to UB (reading from
uninitialized a). musl enables -Wsequence-point, so building with
--enable-warnings is important to catch such issues.

>  
> - memset(byteset, 0, sizeof byteset);
> for (; *c && BITOP(byteset, *(unsigned char *)c, |=); c++);
> - for (; *s && !BITOP(byteset, *(unsigned char *)s, &); s++);
> - return s-a;
> + for (a=s; *a && !BITOP(byteset, *(unsigned char *)a, &); a++);
> + return a-s;
> }

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