From 4d0a82170a25464c39522d7190b9fe302045ddb2 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 26 Sep 2018 14:39:10 -0400 Subject: fix aliasing-based undefined behavior in string functions use the GNU C may_alias attribute if available, and fallback to naive byte-by-byte loops if __GNUC__ is not defined. this patch has been written to minimize changes so that history remains reviewable; it does not attempt to bring the affected code into a more consistent or elegant form. --- src/string/strchrnul.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'src/string/strchrnul.c') diff --git a/src/string/strchrnul.c b/src/string/strchrnul.c index f2b9ae11..39e2635b 100644 --- a/src/string/strchrnul.c +++ b/src/string/strchrnul.c @@ -9,16 +9,19 @@ char *__strchrnul(const char *s, int c) { - size_t *w, k; - c = (unsigned char)c; if (!c) return (char *)s + strlen(s); +#ifdef __GNUC__ + typedef size_t __attribute__((__may_alias__)) word; + const word *w; for (; (uintptr_t)s % ALIGN; s++) if (!*s || *(unsigned char *)s == c) return (char *)s; - k = ONES * c; + size_t k = ONES * c; for (w = (void *)s; !HASZERO(*w) && !HASZERO(*w^k); w++); - for (s = (void *)w; *s && *(unsigned char *)s != c; s++); + s = (void *)w; +#endif + for (; *s && *(unsigned char *)s != c; s++); return (char *)s; } -- cgit v1.2.1