fix aliasing-based undefined behavior in string functions

[musl] / src / string / stpcpy.c

diff --git a/src/string/stpcpy.c b/src/string/stpcpy.c
index 10ca493..4db46a9 100644 (file)
--- a/src/string/stpcpy.c
+++ b/src/string/stpcpy.c
@@ -1,26 +1,26 @@
 #include <string.h>
-#include <stdlib.h>
 #include <stdint.h>
 #include <limits.h>
-#include "libc.h"
 
-#define ALIGN (sizeof(size_t)-1)
+#define ALIGN (sizeof(size_t))
 #define ONES ((size_t)-1/UCHAR_MAX)
 #define HIGHS (ONES * (UCHAR_MAX/2+1))
 #define HASZERO(x) ((x)-ONES & ~(x) & HIGHS)
 
-char *__stpcpy(char *d, const char *s)
+char *__stpcpy(char *restrict d, const char *restrict s)
 {
-       size_t *wd;
-       const size_t *ws;
-
-       if (((uintptr_t)s & ALIGN) == ((uintptr_t)d & ALIGN)) {
-               for (; (*d=*s) && ((uintptr_t)s & ALIGN); s++, d++);
-               if (!*s) return d;
+#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;
                wd=(void *)d; ws=(const void *)s;
                for (; !HASZERO(*ws); *wd++ = *ws++);
                d=(void *)wd; s=(const void *)ws;
        }
+#endif
        for (; (*d=*s); s++, d++);
 
        return d;