Bug #106662 for TermReadKey: ReadKey from empty string causes segfault under cygwin/perl 5.14.4

Wed Aug 26 03:32:01 2015 Luke.Goodsell [...] ogt.com - Ticket created

Subject:	ReadKey from empty string causes segfault under cygwin/perl 5.14.4
Date:	Wed, 26 Aug 2015 07:31:35 +0000
To:	"bug-TermReadKey [...] rt.cpan.org" <bug-TermReadKey [...] rt.cpan.org>
From:	Luke Goodsell <Luke.Goodsell [...] ogt.com>

Hi, Please can you help me to diagnose this issue? I reported it first to the Cygwin mailing list, but was directed to report it to the Term::ReadKey bug tracker. Attempting Term::ReadKey from an empty string under Cygwin with Perl 5.14.4 causes perl to segmentation fault. The same command on Debian with Perl 5.14.2, or with a non-empty string, works fine. Example command: Show quoted text

> perl -MTerm::ReadKey -we 'my $input = ""; open(my $stdin, "<", \$input) or die "failed to open: $!"; local *STDIN = $stdin; ReadMode "raw"; my $response = ReadKey(1, \*STDIN); ReadMode "normal"; if(defined($response)) { print "Got \"$response\"\n"; } else { print "Got undef\n"; }'

Response under cygwin: Show quoted text

> Segmentation fault (core dumped)

Response under Debian: Show quoted text

> Got ""

Changing $input to anything non-empty works properly in both environments. Cygwin dll version: 1.7.32 Perl version: 5.14.4 Term::ReadKey version: 2.33 Kind regards, Luke

Mon Aug 31 07:38:36 2015 jns [...] gellyfish.co.uk - Correspondence added

Subject:	Re: [rt.cpan.org #106662] ReadKey from empty string causes segfault under cygwin/perl 5.14.4
Date:	Mon, 31 Aug 2015 12:38:20 +0100
To:	bug-TermReadKey [...] rt.cpan.org
From:	Jonathan Stowe <jns [...] gellyfish.co.uk>

Hi, Thanks for this. Unfortunately I am unable to test on cygwin and the code as it stands has no special provision for cygwin at all, so it might take a while to fix this. I would hazard guess that it is in fact a bug in something other than Term::ReadKey that is causing the segfault (in that the API of something or other is behaving differently with Cygwin.) If however you could provide a gdb backtrace that illustrates the seqfault this might make it easier to diagnose. Also is it possible for you to try this with a newer perl? It is entirely possible that if the bug infact resides in Perl then it has already been fixed. Thanks again. On Wed, 2015-08-26 at 03:32 -0400, Luke Goodsell via RT wrote: Show quoted text

> Wed Aug 26 03:32:01 2015: Request 106662 was acted upon. > Transaction: Ticket created by Luke.Goodsell@ogt.com > Queue: TermReadKey > Subject: ReadKey from empty string causes segfault under cygwin/perl 5.14.4 > Broken in: (no value) > Severity: (no value) > Owner: Nobody > Requestors: Luke.Goodsell@ogt.com > Status: new > Ticket <URL: https://rt.cpan.org/Ticket/Display.html?id=106662 > > > > Hi, > > Please can you help me to diagnose this issue? I reported it first to the Cygwin mailing list, but was directed to report it to the Term::ReadKey bug tracker. > > Attempting Term::ReadKey from an empty string under Cygwin with Perl 5.14.4 causes perl to segmentation fault. The same command on Debian with Perl 5.14.2, or with a non-empty string, works fine. > > Example command: >

> > perl -MTerm::ReadKey -we 'my $input = ""; open(my $stdin, "<", \$input) or die "failed to open: $!"; local *STDIN = $stdin; ReadMode "raw"; my $response = ReadKey(1, \*STDIN); ReadMode "normal"; if(defined($response)) { print "Got \"$response\"\n"; } else { print "Got undef\n"; }'

> > Response under cygwin: >

> > Segmentation fault (core dumped)

> > Response under Debian: >

> > Got ""

> > Changing $input to anything non-empty works properly in both environments. > > Cygwin dll version: 1.7.32 > Perl version: 5.14.4 > Term::ReadKey version: 2.33 > > Kind regards, > Luke > >

Mon Aug 31 07:38:38 2015 The RT System itself - Status changed from 'new' to 'open'

Tue Sep 01 05:33:01 2015 Luke.Goodsell [...] ogt.com - Correspondence added

Subject:	RE: [rt.cpan.org #106662] ReadKey from empty string causes segfault under cygwin/perl 5.14.4
Date:	Tue, 1 Sep 2015 09:32:40 +0000
To:	"bug-TermReadKey [...] rt.cpan.org" <bug-TermReadKey [...] rt.cpan.org>
From:	Luke Goodsell <Luke.Goodsell [...] ogt.com>

Hi Jonathan, Thanks for responding. I am using the latest Perl available in Cygwin. A perl -d:Trace shows the last calls being: ... Show quoted text

>> (eval 2)[/cygdrive/c/Users/LukeG/lib/perl5/cygwin-thread-multi/Term/ReadKey.pm:501]:3: if(defined $_[0] && $_[0]>0) { >> (eval 2)[/cygdrive/c/Users/LukeG/lib/perl5/cygwin-thread-multi/Term/ReadKey.pm:501]:4: if($_[0]) {return undef if &selectfile($File,$_[0])==0} >> (eval 2)[/cygdrive/c/Users/LukeG/lib/perl5/cygwin-thread-multi/Term/ReadKey.pm:501]:4: if($_[0]) {return undef if &selectfile($File,$_[0])==0}

While running the script in gdb gives: Starting program: /usr/bin/perl test.pl [New Thread 10972.0x1ff0] [New Thread 10972.0x2db8] Program received signal SIGSEGV, Segmentation fault. 0x0000000464563df7 in selectfile () from C:/Users/LukeG/lib/perl5/cygwin-thread-multi/auto/Term/ReadKey/ReadKey.dll (gdb) bt #0 0x0000000464563df7 in selectfile () from C:/Users/LukeG/lib/perl5/cygwin-thread-multi/auto/Term/ReadKey/ReadKey.dll #1 0x0000000464563f97 in XS_Term__ReadKey_selectfile () from C:/Users/LukeG/lib/perl5/cygwin-thread-multi/auto/Term/ReadKey/ReadKey.dll #2 0x00000005e97197b0 in cygperl5_14!Perl_pp_entersub () from /usr/bin/cygperl5_14.dll #3 0x00000005e9711826 in cygperl5_14!Perl_runops_standard () from /usr/bin/cygperl5_14.dll #4 0x00000005e96a0286 in perl_run () from /usr/bin/cygperl5_14.dll #5 0x000000010040220a in perl!main () If I step inspect the selectfile input in the perl debugger I get the following: $ perl -d test.pl Loading DB routines from perl5db.pl version 1.33 Editor support available. Enter h or `h h' for help, or `man perldebug' for more help. main::(test.pl:7): my $input = ""; DB<1> b Term::ReadKey::ReadKey DB<2> c Term::ReadKey::ReadKey((eval 5)[/cygdrive/c/Users/LukeG/lib/perl5/cygwin-thread-multi/Term/ReadKey.pm:501]:2): 2: my($File) = normalizehandle((@_>1?$_[1]:\*STDIN)); DB<2> n Term::ReadKey::ReadKey((eval 5)[/cygdrive/c/Users/LukeG/lib/perl5/cygwin-thread-multi/Term/ReadKey.pm:501]:3): 3: if(defined $_[0] && $_[0]>0) { DB<2> p $File GLOB(0x600076f10) DB<3> p $_[0] 1 DB<4> step DB<5> n Term::ReadKey::ReadKey((eval 5)[/cygdrive/c/Users/LukeG/lib/perl5/cygwin-thread-multi/Term/ReadKey.pm:501]:4): 4: if($_[0]) {return undef if &selectfile($File,$_[0])==0} DB<5> n Term::ReadKey::ReadKey((eval 5)[/cygdrive/c/Users/LukeG/lib/perl5/cygwin-thread-multi/Term/ReadKey.pm:501]:4): 4: if($_[0]) {return undef if &selectfile($File,$_[0])==0} DB<5> n Signal SEGV at test.pl line 15. Aborted (core dumped) The problem appears to lie with selectfile(). I'm not sure how to debug the compiled ReadKey component; can you offer any suggestions? Kind regards, Luke