linux-kernel - Re: [PATCH] tags: fix use of parenthesis in regex

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Message-ID: <20120224165602.6fe303d3@nehalam.linuxnetplumber.net>
Date:	Fri, 24 Feb 2012 16:56:02 -0800
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Michal Marek <mmarek@...e.cz>
Cc:	Stephen Boyd <sboyd@...eaurora.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tags: fix use of parenthesis in regex

On Sat, 25 Feb 2012 01:34:12 +0100
Michal Marek <mmarek@...e.cz> wrote:

> On Mon, Feb 06, 2012 at 03:15:43PM -0800, Stephen Hemminger wrote:
> > Several of the regular expressions passed to etags and ctags where incorrect
> > and missing the backslash before the closing paren, and matching the wrong
> > part of the start of the function causing warning:
> >   etags: Unmatched ( or \( while compiling pattern
> 
> But your patch introduces another imbalances, e.g.
> 
> 
> > @@ -129,31 +129,31 @@ exuberant()
> ...
> > -	--regex-c++='/^TRACE_EVENT\(([^,)]*).*/trace_\1/'		\
> ...
> > +	--regex-c++='/^TRACE_EVENT(\([^,)]*\).*/trace_\1/'		\
> 
> The old version had left paren, start of group, ..., end of group
> The new version has start of group, left paren, ..., right paren
> 
> Where left / right paren means the character without any special
> meaning. I actually can't see anything wrong with the old TRACE_EVENT matching, the regular expression is correct and I think it does what it should do (turn
> TRACE_EVENT(foo) into trace_foo).
> 
> Below is the full list of warnings I get from
> 
> Exuberant Ctags 5.8, Copyright (C) 1996-2009 Darren Hiebert
>   Addresses: <dhiebert@...rs.sourceforge.net>, http://ctags.sourceforge.net
>   Optional compiled features: +wildcards, +regex
> 
> 
>   GEN     tags
> ctags: Warning: regcomp ^SYSCALL_DEFINE[[:digit:]]?(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp ^TRACE_EVENT(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp ^DEFINE_EVENT\([^,)]*, *([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp PAGEFLAG(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp PAGEFLAG(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp PAGEFLAG(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp TESTSETFLAG(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp TESTPAGEFLAG(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp SETPAGEFLAG(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp __SETPAGEFLAG(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp TESTCLEARFLAG(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp __TESTCLEARFLAG(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp CLEARPAGEFLAG(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp __CLEARPAGEFLAG(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp __PAGEFLAG(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp __PAGEFLAG(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp PAGEFLAG_FALSE(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp TESTSCFLAG(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp TESTSCFLAG(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp SETPAGEFLAG_NOOP(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp CLEARPAGEFLAG_NOOP(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp __CLEARPAGEFLAG_NOOP(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp TESTCLEARFLAG_FALSE(\([^,)]*\).*: Unmatched ( or \(
> ctags: Warning: regcomp __TESTCLEARFLAG_FALSE(\([^,)]*\).*: Unmatched ( or \(
> 
> The same list repeats, as ctags is called multiple times.
> 
> Michal

The problem is that in proper regex each start of sub-expression \(
needs to have a matching end of sub-expression \)
The old version had no matching-end of sub-expression and therefore was technically
malformed, probably old tools just ignored it.

   --regex='/PAGEFLAG\(([^,)]*).*/Page\1/'
                      ^
                      start but no end?

My initial patch just fixed those, but others kept wanting more.

  

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