a possible Perl bug about IO::String and $/ in Perl 5.8.6 on Linux/Solaris/MacOS X

[p5pRT]

Migrated from rt.perl.org#35929 (status was 'resolved')

Searchable as RT35929$

[p5pRT]

From hseuming@cs.nyu.edu

Dear fellow Perl lovers\,

The Perl version i use is 5.8.6 on Linux\, Mac OS X\, and Sun Solaris 8.

The following self-contained program dies with a "read failed" message​:

  #!/usr/local/bin/perl -w

  use strict;

  my $s = \<\<'EOF';   line A   line B   a third line   EOF

  open (F\, '\<'\, \$s)   or die "Could not open string as a file";   local $/ = "";   my $ln = \;   die "read failed" unless defined $ln;   close F;

However\, if I have it read from a file with the same contents as $s instead of $s itself\, it succeeds. To wit​:

  #!/usr/local/bin/perl -w

  use strict;

  my $s = \<\<'EOF';   line A   line B   a third line   EOF

  open (F\, '>'\, "/var/tmp/Z");   print F $s;   close F;

  open (F\, '\<'\, "/var/tmp/Z")   or die "Could not open string as a file";   local $/ = "";   my $ln = \;   die "read failed" unless defined $ln;   close F;

This looks like a bona-fide Perl bug. Am I missing something?

Note that reading from them works fine as long as I don't touch $/.

-- Hseuming

---

Emails :​: hseuming.chen@​citigroup.com hseuming@​cs.nyu.edu   hseuming@​gnu.mit.edu hseuming@​yahoo.com   hseuming@​gmail.com hseuming@​hotmail.com

Phones :​: (908)563-0029 (o) (973)597-1801 (h) --------------------------------------------------------------_

[p5pRT]

From @schwern

On Sun\, May 22\, 2005 at 06​:09​:41AM -0000\, Hseu-Ming Chen wrote​:

The following self-contained program dies with a "read failed" message​:

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

use strict;

my $s = \<\<'EOF'; line A line B a third line EOF

open (F\, '\<'\, \$s) or die "Could not open string as a file"; local $/ = ""; my $ln = \; die "read failed" unless defined $ln; close F;

Note that reading from them works fine as long as I don't touch $/.

Yeah\, I can repeat this bug and confirm that "local $/ = ''"; is the problem. Interestingly\, "local $/;" works as does "local $/ = undef;".

-- Michael G Schwern schwern@​pobox.com http​://www.pobox.com/~schwern Don't try the paranormal until you know what's normal.   -- "Lords and Ladies" by Terry Prachett

[p5pRT]

The RT System itself - Status changed from 'new' to 'open'

[p5pRT]

From @rgarcia

On 22 May 2005 06​:09​:41 -0000\, via RT Hseu-Ming Chen \perlbug\-followup@&#8203;perl\.org wrote​:

The following self-contained program dies with a "read failed" message​:

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

use strict;

my $s = \<\<'EOF'; line A line B a third line EOF

open (F\, '\<'\, \$s) or die "Could not open string as a file"; local $/ = ""; my $ln = \; die "read failed" unless defined $ln; close F;

The bug is in PerlIOScalar_unread\, which doesn't do what it should. The following patch solves this particular problem\, but it's obviously not sufficient... it's late and I'll try to work out a proper solution another day.

==== //depot/perl/ext/PerlIO/scalar/scalar.xs#12 - /opt/bleadperl/p4/perl/ext/PerlIO/scalar/scalar.xs ==== --- /home/rafael/tmp/tmp.21342.0 2005-05-23 00​:36​:44.351368184 +0200 +++ /opt/bleadperl/p4/perl/ext/PerlIO/scalar/scalar.xs 2005-05-23 00​:36​:37.732374424 +0200 @​@​ -105\,11 +105\,7 @​@​ SSize_t PerlIOScalar_unread(pTHX_ PerlIO * f\, const void *vbuf\, Size_t count) {   PerlIOScalar *s = PerlIOSelf(f\, PerlIOScalar); - char *dst = SvGROW(s->var\, (STRLEN)s->posn + count); - Move(vbuf\, dst + s->posn\, count\, char); - s->posn += count; - SvCUR_set(s->var\, (STRLEN)s->posn); - SvPOK_on(s->var); + s->posn -= count;   return count; }

[p5pRT]

From @rgarcia

On 5/23/05\, Rafael Garcia-Suarez \rgarciasuarez@&#8203;gmail\.com wrote​:

The bug is in PerlIOScalar_unread\, which doesn't do what it should. The following patch solves this particular problem\, but it's obviously not sufficient... it's late and I'll try to work out a proper solution another day.

Now hopefully implemented in bleadperl as :

Change 24543 on 2005/05/23 by rgs@​marais

  Fix [perl #35929] : PerlIO​::scalar didn't understand $/ = ""   because PerlIOScalar_unread was broken.   Bump version number of PerlIO​::scalar to 0.04.

[p5pRT]

@rgs - Status changed from 'open' to 'resolved'