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/strlen.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'src/string/strlen.c') diff --git a/src/string/strlen.c b/src/string/strlen.c index 929ddcbc..309990f0 100644 --- a/src/string/strlen.c +++ b/src/string/strlen.c @@ -10,9 +10,13 @@ size_t strlen(const char *s) { const char *a = s; - const size_t *w; +#ifdef __GNUC__ + typedef size_t __attribute__((__may_alias__)) word; + const word *w; for (; (uintptr_t)s % ALIGN; s++) if (!*s) return s-a; for (w = (const void *)s; !HASZERO(*w); w++); - for (s = (const void *)w; *s; s++); + s = (const void *)w; +#endif + for (; *s; s++); return s-a; } -- cgit v1.2.1