Messages in this thread | | | Subject | Re: [for-next][PATCH 23/24] string.h: Add strncmp_prefix() helper macro | From | Rasmus Villemoes <> | Date | Sun, 23 Dec 2018 23:01:52 +0100 |
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On 21/12/2018 23.20, Joe Perches wrote: > On Fri, 2018-12-21 at 16:08 -0500, Steven Rostedt wrote: >> On Fri, 21 Dec 2018 21:58:32 +0100 >> Andreas Schwab <schwab@linux-m68k.org> wrote: >> >> >>>> Well, perhaps I can just remove the ending ones. I get paranoid with >>>> macro variables, and tend to over do it so that there's no question. >>> >>> Why not make it an inline function? >> >> Matters if that removes the strlen(const) optimization. I could try it >> and see what happens. > > Using > > static inline bool str_has_prefix(const char *str, const char prefix[]) > { > return !strncmp(str, prefix, strlen(prefix)); > } >
We already have exactly that function, it's called strstarts().
commit 66f92cf9d415e96a5bdd6c64de8dd8418595d2fc Author: Rusty Russell <rusty@rustcorp.com.au> Date: Tue Mar 31 13:05:36 2009 -0600
strstarts: helper function for !strncmp(str, prefix, strlen(prefix))
Please don't add a copy under another name.
As for converting existing users, go for it. FWIW, I ran a cocci script a few years ago to find suspicious strncmp() cases, and there were some (e87c3f, ca957b6), but fewer than I expected. There are some confused/confusing ones that apparently deliberately do strncmp(a, b, sizeof(b)) instead of the equivalent to strcmp(a, b) (e.g. 'strncmp(str, "hwc", 4) == 0')
Rasmus
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