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From: arnold@skeeve.com
To: bug-gnulib@gnu.org, bruno@clisp.org
Cc: eggert@cs.ucla.edu, arnold@skeeve.com
Subject: Re: possible bug in regex and dfa
Date: Sun, 18 Jul 2021 13:30:57 -0600	[thread overview]
Message-ID: <202107181930.16IJUvI3011225@freefriends.org> (raw)
In-Reply-To: <3323531.JAME3IizvO@omega>

Hi.

Bruno Haible <bruno@clisp.org> wrote:

>   - if REG_NEWLINE is not set, '.' matches newline but '^' does not match
>     after the newline.

This is indeed the desired behavior, but regex isn't following it.

REG_NEWLINE being set gets translated into preg->newline_anchor. 

Starting at line 620, regexec.c relates to it:

|   /* If initial states with non-begbuf contexts have no elements,
|      the regex must be anchored.  If preg->newline_anchor is set,
|      we'll never use init_state_nl, so do not check it.  */
|   if (dfa->init_state->nodes.nelem == 0
|       && dfa->init_state_word->nodes.nelem == 0
|       && (dfa->init_state_nl->nodes.nelem == 0
| 	  || !preg->newline_anchor))
|     {
|       if (start != 0 && last_start != 0)
|         return REG_NOMATCH;
|       start = last_start = 0;
|     }

(As a side note, I don't think the comment matches the code.)

In my case, preg->newline_anchor is zero (correctly), but
dfa->init_state->nodes.nelem is not, so this body isn't executed.
Making the test for preg->newline_anchor the first thing causes my test
case to work correctly but breaks the gawk test suite.

In other words, I think the bug is somewhere in this area, but I
don't understand the regex internals enough to fix it.  dfa will also
need looking at.

Thanks,

Arnold


      parent reply	other threads:[~2021-07-18 19:31 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-15 18:48 possible bug in regex and dfa Arnold Robbins
2021-07-17  2:58 ` Paul Eggert
2021-07-18  9:01   ` Bruno Haible
2021-07-18 12:56   ` arnold
2021-07-18 16:09     ` Bruno Haible
2021-07-18 18:59       ` arnold
2021-07-18 21:45         ` regex unit tests Bruno Haible
2021-07-18 19:30       ` arnold [this message]

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