Messages in this thread | ![/](/images/icornerl.gif) | | Date | Sun, 23 Dec 2018 17:56:21 -0500 | From | Steven Rostedt <> | Subject | Re: [for-next][PATCH 23/24] string.h: Add strncmp_prefix() helper macro |
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On Sun, 23 Dec 2018 23:01:52 +0100 Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:
> 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().
It's not exact.
> > 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')
Well, one thing that str_has_prefix() does that strstarts() does not, is to return the prefix length which gets rid of the duplication.
Would it be OK to convert strstarts() to return the length of prefix?
-- Steve
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