Missed optimization of strcpy(3) (or stpcpy(3))

[Alejandro Colomar via Gcc]

Hi,

The following code can be optimized to use memcpy(3), since the length
of the copy is known (we've just called strnlen(3), and discarded the
possibility of truncated lengths).

$ cat strxcpy.c
#include <stddef.h>
#include <string.h>
#include <sys/types.h>

ssize_t
strxcpy(char *restrict dst, const char *restrict src, size_t dsize)
{
        if (strnlen(src, dsize) == dsize)
                return -1;

        return stpcpy(dst, src) - dst;
}


This compiles to stpcpy(3).  Similar code written with strcpy(3) also
keeps strcpy(3).  But they could be optimized with mempcpy(3) or
memcpy(3).


Thanks,
Alex

-- 
<https://www.alejandro-colomar.es/>

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