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.

diff --git a/src/multibyte/mbrtowc.c b/src/multibyte/mbrtowc.c
index 35e834ee6af711da7d6ab077d0674966d690bba7..e7b365403bbb0532a161b95a14f15931d3bf2521 100644 (file)
--- 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 6710637ade41ee0cc1f8bc5d3d07b333561ac11c..803d2213d7bd3238fa9bb31cf5269d0da7ab612c 100644 (file)
--- 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;