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/stpncpy.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'src/string/stpncpy.c') diff --git a/src/string/stpncpy.c b/src/string/stpncpy.c index d6d92ffc..f57fa6b7 100644 --- a/src/string/stpncpy.c +++ b/src/string/stpncpy.c @@ -9,9 +9,10 @@ char *__stpncpy(char *restrict d, const char *restrict s, size_t n) { - size_t *wd; - const size_t *ws; - +#ifdef __GNUC__ + typedef size_t __attribute__((__may_alias__)) word; + word *wd; + const word *ws; if (((uintptr_t)s & ALIGN) == ((uintptr_t)d & ALIGN)) { for (; ((uintptr_t)s & ALIGN) && n && (*d=*s); n--, s++, d++); if (!n || !*s) goto tail; @@ -20,6 +21,7 @@ char *__stpncpy(char *restrict d, const char *restrict s, size_t n) n-=sizeof(size_t), ws++, wd++) *wd = *ws; d=(void *)wd; s=(const void *)ws; } +#endif for (; n && (*d=*s); n--, s++, d++); tail: memset(d, 0, n); -- cgit v1.2.1