Re: [TRIVIAL] strlen("literal string") -> (sizeof("literal string")-1)

Jim Treadway
2002-08-28T21:51:29Z

On Wed, 28 Aug 2002 junkio@cox.net wrote:

> Here is a patch that does the same as what Keith Owens did in
> his patch recently.
>
> Message-ID: <fa.iks3ohv.1flge08@ifi.uio.no>
> From: Keith Owens <kaos@ocs.com.au>
> Subject: [patch] 2.4.19 Generate better code for nfs_sillyrename
> Date: Wed, 28 Aug 2002 07:08:17 GMT
>
> Using strlen() generates an unnecessary inline function expansion plus
> dynamic stack adjustment. For constant strings, strlen() == sizeof()-1
> and the object code is better.
>
> The patch is against 2.4.19.
>
> diff -ru 2.4.19/arch/mips/hp-lj/utils.c 2.4.19-strlen/arch/mips/hp-lj/utils.c
> --- 2.4.19/arch/mips/hp-lj/utils.c 2002-08-02 10:48:43.000000000 -0700
> +++ 2.4.19-strlen/arch/mips/hp-lj/utils.c 2002-08-28 01:17:20.000000000 -0700
> @@ -48,7 +48,7 @@
> {
> char* pos = strstr(cl, "reserved_buffer=");
> if (pos) {
> - buffer_size = simple_strtol(pos+strlen("reserved_buffer="),
> + buffer_size = simple_strtol(pos+(sizeof("reserved_buffer=")-1),
> 0, 10);
> buffer_size <<= 20;
> if (buffer_size + MIN_GEN_MEM > base_mem)

Would redefining strlen() as __strlen() and then using

#define strlen(x) (__builtin_constant_p(x) ? (sizeof(x) - 1) : __strlen(x))

work in this situation?

Jim