path: root/src/string/strlen.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/strlen.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/strlen.c')
1 files changed, 6 insertions, 2 deletions
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;
+ for (; *s; s++);
return s-a;