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/memmove.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'src/string/memmove.c') diff --git a/src/string/memmove.c b/src/string/memmove.c index f225bb30..5dc9cdb9 100644 --- a/src/string/memmove.c +++ b/src/string/memmove.c @@ -1,8 +1,10 @@ #include #include -#define WT size_t +#ifdef __GNUC__ +typedef __attribute__((__may_alias__)) size_t WT; #define WS (sizeof(WT)) +#endif void *memmove(void *dest, const void *src, size_t n) { @@ -13,6 +15,7 @@ void *memmove(void *dest, const void *src, size_t n) if ((uintptr_t)s-(uintptr_t)d-n <= -2*n) return memcpy(d, s, n); if (d=WS; n-=WS, d+=WS, s+=WS) *(WT *)d = *(WT *)s; } +#endif for (; n; n--) *d++ = *s++; } else { +#ifdef __GNUC__ if ((uintptr_t)s % WS == (uintptr_t)d % WS) { while ((uintptr_t)(d+n) % WS) { if (!n--) return dest; @@ -29,6 +34,7 @@ void *memmove(void *dest, const void *src, size_t n) } while (n>=WS) n-=WS, *(WT *)(d+n) = *(WT *)(s+n); } +#endif while (n) n--, d[n] = s[n]; } -- cgit v1.2.1