Re: [9front] strndup should use strnlen and memcpy

[tlaronde@polynum.com]

On Fri, Dec 18, 2020 at 09:38:00AM +0100, Sigrid Solveig Haflínudóttir wrote:
> In 9front, memcpy == memmove.
> 
> Why is strlen dangerous?

Because the terminating '\0' may not be here. But it's simpler to inline:

size_t l;

for (l = 0; l < n && s[l]; l++)
	;

preceeded by an assertion about the not 'nil'ity of s.

FWIW,

T. Laronde

> Date: Fri, 18 Dec 2020 02:22:25 -0600
> From: Xiao-Yong Jin <meta.jxy@gmail.com>
> Subject: [9front] strndup should use strnlen and memcpy
> To: 9front@9front.org
> X-Mailer: Apple Mail (2.3654.40.0.2.32)
> 
> I just saw the new commit of strndup that uses strlen and memmove.
> memmove is unnecessary.
> strlen is dangerous.
> 
> Here is a reference implementation from musl.
> 
> http://git.musl-libc.org/cgit/musl/tree/src/string/strndup.c
> 
> #include <stdlib.h>
> #include <string.h>
> 
> char *strndup(const char *s, size_t n)
> {
> 	size_t l = strnlen(s, n);
> 	char *d = malloc(l+1);
> 	if (!d) return NULL;
> 	memcpy(d, s, l);
> 	d[l] = 0;
> 	return d;
> }


-- 
        Thierry Laronde <tlaronde +AT+ polynum +dot+ com>
                     http://www.kergis.com/
                    http://kertex.kergis.com/
                       http://www.sbfa.fr/
Key fingerprint = 0FF7 E906 FBAF FE95 FD89  250D 52B1 AE95 6006 F40C