linux-kernel - Re: CONFIG_KPROBES=y build requires gawk

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Date:	Wed, 16 Dec 2009 23:56:51 -0500
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Roland Dreier <rdreier@...co.com>
CC:	Andrew Isaacson <adi@...are.com>, Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
	Rob Landley <rob@...dley.net>
Subject: Re: CONFIG_KPROBES=y build requires gawk

Roland Dreier wrote:
> 
>  >        For  example,  before the POSIX standard, to match alphanumeric charac-
>  >        ters, you would have had to write /[A-Za-z0-9]/.  If your character set
>  >        had  other  alphabetic characters in it, this would not match them, and
>  >        if your character set collated differently from ASCII, this  might  not
>  >        even match the ASCII alphanumeric characters.  With the POSIX character
>  >        classes, you can write /[[:alnum:]]/, and this matches  the  alphabetic
>  >        and numeric characters in your character set, no matter what it is.
> 
> I'm not sure I understand this, although I'm not a character set expert.
> But is there really some possible locale + awk implementation where an
> awk script, written in pure ASCII, operating on a pure ASCII input file,
> will have [A-Za-z0-9] match a different set of ASCII characters than
> [[:alnum:]] will match?

I assume that in utf-8 locale(nowadays default in most of distro) alphabets
may be sorted as aAbBcC...zZ(or AaBb...), and in this case a-z means
aAbBcC...z.

As Al Viro said, if we run awk with LC_ALL=C, then the characters will be
sorted as ASCII. So, your patch is OK if you can add LC_ALL=C just before
$(AWK). (I'm not so sure whether Makefile can accept it...)

Thank you,

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com

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