Re: [PATCH] regex: fix match with possessive quantifier

[Dmitry V. Levin]

On Mon, Jun 07, 2021 at 04:10:27AM +0300, Dmitry V. Levin wrote:
> On Mon, Jun 07, 2021 at 12:45:02AM +0300, Dmitry V. Levin wrote:
> > On Wed, May 26, 2021 at 12:08:19PM +0300, Egor Ignatov wrote:
> > > Fix behaviour introduced in 70b673e, where regexps with
> > > possessive quantifier("*+") didn't match.
> > > * lib/regexec.c
> > > (set_regs): Pop if CUR_NODE has already been checked only when
> > > we have a fail stack.
> > > 
> > > Signed-off-by: Egor Ignatov <egori@altlinux.org>
> > > ---
> > > Hi Paul,
> > > 
> > > Do you have any test cases for bug 11053(glibc) for gnulib?
> > > This patch fixes the issue with "*+", but I'm not sure it
> > > doesn't break your fix for 11053.
> > 
> > Thanks, the fix looks plausible, it doesn't break any tests
> > (including those introduced along with commit 70b673eb7),
> 
> Apparently, there are more issues with commit 70b673eb7, for example:
> 
> $ echo ab | sed -E 's/^(a*)*(.)\1/\1/'
> Segmentation fault
> 
> $ echo ab | strace -enone -- sed --debug -E 's/^(a*)*(.)\1/\1/'
> SED PROGRAM:
>   s/^(a*)*(.)\\1/\1/
> INPUT:   'STDIN' line 1
> PATTERN: ab
> COMMAND: s/^(a*)*(.)\\1/\1/
> MATCHED REGEX REGISTERS
>   regex[0] = 0-2 'ab'
>   regex[1] = 0--1 'ab!!ab
> '
> --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0x20} ---
> +++ killed by SIGSEGV +++
> Segmentation fault

And here is a tests/test-regex.c entry for this bug:

diff --git a/tests/test-regex.c b/tests/test-regex.c
index 7ea73cfb6..fdb1a1f1d 100644
--- a/tests/test-regex.c
+++ b/tests/test-regex.c
@@ -120,6 +120,8 @@ static struct
   { "^a*+(.)", "ab", REG_EXTENDED, 2, { { 0, 2 }, { 1, 2 } } },
   /* Test for ** match.  */
   { "^(a*)*(.)", "ab", REG_EXTENDED, 3, { { 0, 2 }, { 0, 1 }, { 1, 2 } } },
+  /* Test for ** match with backreferences.  */
+  { "^(a*)*\\1", "a", REG_EXTENDED, 2, { { 0, 0 }, { 0, 0 } } },
 };
 
 static void


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