Rich Felker
4d0a82170a
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.
30 lines
685 B
C
30 lines
685 B
C
#include <string.h>
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#include <stdint.h>
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#include <limits.h>
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#define ALIGN (sizeof(size_t))
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#define ONES ((size_t)-1/UCHAR_MAX)
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#define HIGHS (ONES * (UCHAR_MAX/2+1))
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#define HASZERO(x) ((x)-ONES & ~(x) & HIGHS)
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char *__stpcpy(char *restrict d, const char *restrict s)
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{
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#ifdef __GNUC__
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typedef size_t __attribute__((__may_alias__)) word;
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word *wd;
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const word *ws;
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if ((uintptr_t)s % ALIGN == (uintptr_t)d % ALIGN) {
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for (; (uintptr_t)s % ALIGN; s++, d++)
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if (!(*d=*s)) return d;
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wd=(void *)d; ws=(const void *)s;
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for (; !HASZERO(*ws); *wd++ = *ws++);
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d=(void *)wd; s=(const void *)ws;
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}
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#endif
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for (; (*d=*s); s++, d++);
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return d;
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}
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weak_alias(__stpcpy, stpcpy);
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