diff options
authorRich Felker <>2014-07-01 18:27:19 -0400
committerRich Felker <>2014-07-28 00:27:58 -0400
commit726df5a8bc03a30afdb123edfeae5da180b77f79 (patch)
parent37eb19e0908697e8ef810cf350a52d2009959f1a (diff)
fix aliasing violations in mbtowc and mbrtowc
these functions were setting wc to point to wchar_t aliasing itself as a "cheap" way to support null wc arguments. doing so was anything but cheap, since even without the aliasing violation, it would limit the compiler's ability to optimize. making wc point to a dummy object is equally easy and does not suffer from the above problems. (cherry picked from commit e89cfe51d2001af08fc2a13e5133ba8157f90beb)
2 files changed, 4 insertions, 2 deletions
diff --git a/src/multibyte/mbrtowc.c b/src/multibyte/mbrtowc.c
index 35e834ee..e7b36540 100644
--- a/src/multibyte/mbrtowc.c
+++ b/src/multibyte/mbrtowc.c
@@ -14,6 +14,7 @@ size_t mbrtowc(wchar_t *restrict wc, const char *restrict src, size_t n, mbstate
unsigned c;
const unsigned char *s = (const void *)src;
const unsigned N = n;
+ wchar_t dummy;
if (!st) st = (void *)&internal_state;
c = *(unsigned *)st;
@@ -21,7 +22,7 @@ size_t mbrtowc(wchar_t *restrict wc, const char *restrict src, size_t n, mbstate
if (!s) {
if (c) goto ilseq;
return 0;
- } else if (!wc) wc = (void *)&wc;
+ } else if (!wc) wc = &dummy;
if (!n) return -2;
if (!c) {
diff --git a/src/multibyte/mbtowc.c b/src/multibyte/mbtowc.c
index 6710637a..803d2213 100644
--- a/src/multibyte/mbtowc.c
+++ b/src/multibyte/mbtowc.c
@@ -12,10 +12,11 @@ int mbtowc(wchar_t *restrict wc, const char *restrict src, size_t n)
unsigned c;
const unsigned char *s = (const void *)src;
+ wchar_t dummy;
if (!s) return 0;
if (!n) goto ilseq;
- if (!wc) wc = (void *)&wc;
+ if (!wc) wc = &dummy;
if (*s < 0x80) return !!(*wc = *s);
if (*s-SA > SB-SA) goto ilseq;