From: Steven Rostedt <rostedt@goodmis.org>
To: Namhyung Kim <namhyung@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Joe Perches <joe@perches.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Tom Zanussi <zanussi@kernel.org>,
Andreas Schwab <schwab@linux-m68k.org>,
kernel-team@lge.com
Subject: Re: [PATCH v4] string.h: Add str_has_prefix() helper function
Date: Sat, 22 Dec 2018 07:24:04 -0500 [thread overview]
Message-ID: <20181222072404.27a7e9a3@vmware.local.home> (raw)
In-Reply-To: <20181222093346.GB7610@danjae.aot.lge.com>
On Sat, 22 Dec 2018 18:33:46 +0900
Namhyung Kim <namhyung@kernel.org> wrote:
> > +static __always_inline size_t str_has_prefix(const char *str, const char *prefix)
> > +{
> > + size_t len = strlen(prefix);
> > + return strncmp(str, prefix, len) == 0 ? len : 0;
>
> As it already knows the length (and it needs to use it for return
> value), isn't it (slightly) better using memcmp() instead?
No, because we don't know the length of str.
[ str = "h\0[bad memory]" ]
str_has_prefix(str, "TEST THIS BIG STRING AT FRONT")
If we use memcmp(), then we are testing way after str has ended, and
that can cause a memory fault.
-- Steve
next prev parent reply other threads:[~2018-12-22 17:48 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-22 4:19 [PATCH v4] string.h: Add str_has_prefix() helper function Steven Rostedt
2018-12-22 4:42 ` Steven Rostedt
2018-12-22 9:33 ` Namhyung Kim
2018-12-22 12:24 ` Steven Rostedt [this message]
2018-12-22 14:24 ` Namhyung Kim
2018-12-22 15:12 ` Steven Rostedt
2018-12-22 16:16 ` Steven Rostedt
2018-12-22 16:46 ` Namhyung Kim
2018-12-22 17:19 ` Steven Rostedt
2018-12-22 17:23 ` Steven Rostedt
2018-12-22 17:24 ` Steven Rostedt
2018-12-23 3:13 ` Namhyung Kim
2018-12-23 3:23 ` Steven Rostedt
2018-12-23 3:05 ` Namhyung Kim
2019-01-11 8:10 ` [utility perl script] strncmp() -> str_has_prefix() conversions Joe Perches
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