Re: [PATCH] lib/string.c: implement stpcpy

Arvind Sankar
2020-08-15T22:04:28Z

On Fri, Aug 14, 2020 at 05:24:15PM -0700, Nick Desaulniers wrote:
> +#ifndef __HAVE_ARCH_STPCPY
> +/**
> + * stpcpy - copy a string from src to dest returning a pointer to the new end
> + * of dest, including src's NULL terminator. May overrun dest.
> + * @dest: pointer to end of string being copied into. Must be large enough
> + * to receive copy.
> + * @src: pointer to the beginning of string being copied from. Must not overlap
> + * dest.
> + *
> + * stpcpy differs from strcpy in two key ways:
> + * 1. inputs must not overlap.
> + * 2. return value is the new NULL terminated character. (for strcpy, the
> + * return value is a pointer to src.
> + */
> +#undef stpcpy
> +char *stpcpy(char *__restrict__ dest, const char *__restrict__ src)
> +{
> + while ((*dest++ = *src++) != '\0')
> + /* nothing */;
> + return dest;
> +}
> +#endif
> +

Won't this return a pointer that's one _past_ the terminating NUL? I
think you need the increments to be inside the loop body, rather than as
part of the condition.

Nit: NUL is more correct than NULL to refer to the string terminator.