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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.
This commit is contained in:
Rich Felker 2014-07-01 18:27:19 -04:00
parent 2d8cc92a7c
commit e89cfe51d2
2 changed files with 4 additions and 2 deletions
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3
src/multibyte/mbrtowc.c
View File

@ -14,6 +14,7 @@ size_t mbrtowc(wchar_t *restrict wc, const char *restrict src, size_t n, mbstate
unsigned c; unsigned c;
const unsigned char *s = (const void *)src; const unsigned char *s = (const void *)src;
const unsigned N = n; const unsigned N = n;
wchar_t dummy;
if (!st) st = (void *)&internal_state; if (!st) st = (void *)&internal_state;
c = *(unsigned *)st; 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 (!s) {
if (c) goto ilseq; if (c) goto ilseq;
return 0; return 0;
} else if (!wc) wc = (void *)&wc; } else if (!wc) wc = &dummy;
if (!n) return -2; if (!n) return -2;
if (!c) { if (!c) {

3
src/multibyte/mbtowc.c
View File

@ -12,10 +12,11 @@ int mbtowc(wchar_t *restrict wc, const char *restrict src, size_t n)
{ {
unsigned c; unsigned c;
const unsigned char *s = (const void *)src; const unsigned char *s = (const void *)src;
wchar_t dummy;
if (!s) return 0; if (!s) return 0;
if (!n) goto ilseq; if (!n) goto ilseq;
if (!wc) wc = (void *)&wc; if (!wc) wc = &dummy;
if (*s < 0x80) return !!(*wc = *s); if (*s < 0x80) return !!(*wc = *s);
if (*s-SA > SB-SA) goto ilseq; if (*s-SA > SB-SA) goto ilseq;