path: root/src/string/stpcpy.c
diff options
authorRich Felker <>2018-09-26 14:39:10 -0400
committerRich Felker <>2018-09-26 14:39:10 -0400
commit4d0a82170a25464c39522d7190b9fe302045ddb2 (patch)
treeb3a469567ed3a995300c9751b824ef20b84f154d /src/string/stpcpy.c
parent8cd738bbee3b4e60a99b71599c338bf444070f18 (diff)
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/stpcpy.c')
1 files changed, 5 insertions, 3 deletions
diff --git a/src/string/stpcpy.c b/src/string/stpcpy.c
index 54cf9ca5..4db46a9e 100644
--- a/src/string/stpcpy.c
+++ b/src/string/stpcpy.c
@@ -9,9 +9,10 @@
char *__stpcpy(char *restrict d, const char *restrict s)
- 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; s++, d++)
if (!(*d=*s)) return d;
@@ -19,6 +20,7 @@ char *__stpcpy(char *restrict d, const char *restrict s)
for (; !HASZERO(*ws); *wd++ = *ws++);
d=(void *)wd; s=(const void *)ws;
for (; (*d=*s); s++, d++);
return d;