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 22:23:33 -0500 [thread overview]
Message-ID: <20181222222333.78eaa7ce@vmware.local.home> (raw)
In-Reply-To: <20181223031343.GB11421@danjae.aot.lge.com>
On Sun, 23 Dec 2018 12:13:43 +0900
Namhyung Kim <namhyung@kernel.org> wrote:
> > Also, I believe there are some memcmp implementations that start at the
> > end of the memory locations, not the beginning. That is, it compares
> > backwards. Which is also legit for memcmp to do.
>
> I'm not sure, the man page says:
>
> RETURN VALUE
> The memcmp() function returns an integer less than, equal to,
> or greater than zero if the first n bytes of s1 is found,
> respectively, to be less than, to match, or be greater than
> the first n bytes of s2.
>
> For a nonzero return value, the sign is determined by the sign
> of the difference between the first pair of bytes (interpreted
> as unsigned char) that differ in s1 and s2.
>
> If n is zero, the return value is zero.
>
>
> It should return difference in the first pair of bytes that differ so
> I guess implementations should compare from the beginning.
Ah, makes sense. I think I'm thinking of memcpy() which can start at
the end, or maybe even the deprecated bcmp(). It's been a long time
since I had to deal with the implementations of these.
-- Steve
next prev parent reply other threads:[~2018-12-23 3:23 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
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 [this message]
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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