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author | Rich Felker <dalias@aerifal.cx> | 2018-09-26 14:39:10 -0400 |
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committer | Rich Felker <dalias@aerifal.cx> | 2018-09-26 14:39:10 -0400 |
commit | 4d0a82170a25464c39522d7190b9fe302045ddb2 (patch) | |
tree | b3a469567ed3a995300c9751b824ef20b84f154d /src/string/memmove.c | |
parent | 8cd738bbee3b4e60a99b71599c338bf444070f18 (diff) | |
download | musl-4d0a82170a25464c39522d7190b9fe302045ddb2.tar.gz |
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.
Diffstat (limited to 'src/string/memmove.c')
-rw-r--r-- | src/string/memmove.c | 8 |
1 files changed, 7 insertions, 1 deletions
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 <string.h> #include <stdint.h> -#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<s) { +#ifdef __GNUC__ if ((uintptr_t)s % WS == (uintptr_t)d % WS) { while ((uintptr_t)d % WS) { if (!n--) return dest; @@ -20,8 +23,10 @@ void *memmove(void *dest, const void *src, size_t n) } for (; n>=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]; } |