Regular expression match (?:XX|X)* dumps core

[p5pRT]

Migrated from rt.perl.org#938 (status was 'resolved')

Searchable as RT938$

[p5pRT]

From garethr@cre.canon.co.uk

The following program causes a segmentation violation​:

  $_ = 'X' x 50000;   /(?​:XX|X)*/;

Perl Info

``` Site configuration information for perl 5.00502: Configured by abw at Thu Nov 19 10:50:08 GMT 1998. Summary of my perl5 (5.0 patchlevel 5 subversion 2) configuration: Platform: osname=solaris, osvers=2.6, archname=sun4-solaris uname='sunos bandanna 5.6 generic_105181-03 sun4u sparc sunw,ultra-1 ' hint=previous, useposix=true, d_sigaction=define usethreads=undef useperlio=undef d_sfio=undef Compiler: cc='gcc', optimize='-O', gccversion=2.8.0 cppflags='-I/opt/gnu/include -I/user/perl/build/include' ccflags ='-I/opt/gnu/include -I/user/perl/build/include' stdchar='unsigned char', d_stdstdio=define, usevfork=false intsize=4, longsize=4, ptrsize=4, doublesize=8 d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16 alignbytes=8, usemymalloc=n, prototype=define Linker and Libraries: ld='gcc', ldflags ='-L/opt/gnu/lib -L/user/perl/build/lib' libpth=/opt/gnu/lib /lib /usr/lib /usr/ccs/lib /user/perl/build/lib libs=-lsocket -lnsl -lgdbm -ldl -lm -lc -lcrypt -ldb libc=/lib/libc.so, so=so, useshrplib=false, libperl=libperl.a Dynamic Linking: dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags=' ' cccdlflags='-fPIC', lddlflags='-G -L/opt/gnu/lib -L/user/perl/build/lib' Locally applied patches: @INC for perl 5.00502: /apps/perl5/lib/5.00502/sun4-solaris /apps/perl5/lib/5.00502 /apps/perl5/lib/site_perl/5.005/sun4-solaris /apps/perl5/lib/site_perl/5.005 . Environment for perl 5.00502: HOME=/user/garethr LANG=C LD_LIBRARY_PATH=/usr/dt/lib:/usr/openwin/lib:/apps/X11R5/lib:/usr/lib LOGDIR (unset) PATH=/usr/dt/bin:/usr/openwin/bin:/bin:/usr/bin:/usr/ucb:/bin:/usr/bin:/cre/bin:/apps/gcc-2.8.0/bin:/apps/frame5/bin:/apps/emacs/bin:/apps/tex/bin:/apps/perl5/bin:/user/web/bin/scripts:/user/web/bin/SunOS-5.6:/apps/gnu/bin:/apps/mysql/bin:/usr/ccs/bin:/apps/X11R5/bin:/usr/openwin/bin PERL_BADLANG (unset) SHELL=/cre/bin/bash ```

[p5pRT]

From [Unknown Contact. See original ticket]

This regexp bug can _still_ cause a segfault in bleadperl as of today.

--cut-- #!/usr/local/bin/perl

$_ = 'X' x 50000; /(?​:XX|X)*/; --cut--

[p5pRT]

From @vanstyn

In \20000918115335\.A27376@​athenaeum\.globnix\.org\, Michael Stevens writes​: :This regexp bug can _still_ cause a segfault in bleadperl as of today. : :--cut-- :#!/usr/local/bin/perl : :$_ = 'X' x 50000; :/(?​:XX|X)*/;

Yes\, this is not likely to be fixed any time soon​: the recursion exceeds your stack size. Increasing the stack size for perl may allow you to match longer strings before it breaks\, but a fix involves flattening the recursion out of the regexp matcher\, which is a) difficult and b) not of the highest priority. But patches welcome\, of course. :)

Hugo

[p5pRT]

From [Unknown Contact. See original ticket]

On Mon\, Sep 18\, 2000 at 01​:33​:17PM +0100\, Hugo wrote​:

Yes\, this is not likely to be fixed any time soon​: the recursion exceeds your stack size. Increasing the stack size for perl may allow you to match longer strings before it breaks\, but a fix involves flattening the recursion out of the regexp matcher\, which is a) difficult and b) not of the highest priority. But patches welcome\, of course. :)

It would be nice if it could at least say "this is too big\, I give up".

Code wise\, the regexp stuff scares me.

Michael.

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From @vanstyn

In \20000918141050\.A29064@​athenaeum\.globnix\.org\, Michael Stevens writes​: :On Mon\, Sep 18\, 2000 at 01​:33​:17PM +0100\, Hugo wrote​: :> Yes\, this is not likely to be fixed any time soon​: the recursion exceeds :> your stack size. Increasing the stack size for perl may allow you to :> match longer strings before it breaks\, but a fix involves flattening :> the recursion out of the regexp matcher\, which is a) difficult and b) :> not of the highest priority. But patches welcome\, of course. :) : :It would be nice if it could at least say "this is too big\, I give up". : :Code wise\, the regexp stuff scares me.

It should do​: that is what the REG_INFTY stuff is there for. However it is difficult (impossible?) for Configure to determine the right value to set REG_INFTY to - I believe it is usually too high under Linux\, for example - and I have seen suggestions that the REG_INFTY check may not be triggered when it should in all cases.

HTH\,

Hugo

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From The RT System itself

still core dumps in bleadperl as of 18/sep/2000\, perl 5.7.0 DEVEL7093