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Globref locally assigned to glob in method doesn't work #1087

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p5pRT opened this issue Jan 25, 2000 · 5 comments
Closed

Globref locally assigned to glob in method doesn't work #1087

p5pRT opened this issue Jan 25, 2000 · 5 comments

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@p5pRT
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p5pRT commented Jan 25, 2000

Migrated from rt.perl.org#2040 (status was 'resolved')

Searchable as RT2040$

@p5pRT
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p5pRT commented Jan 25, 2000

From @mjdominus

I have a trivial module, Mod.pm. It has two methods. The constructor
accepts a globref and creates an object that contains the globref as
member data. The other tries to read a line of data from the
filehandle associated with the globref. However, the data is not
forthcoming.

Here is file '/tmp/t1', my test script​:

================================================================
use Mod;
open TF, "< /tmp/t1" or die;
my $o = Mod->new(FH => \*TF);
my $data = $o->readit;
print $data;

================================================================

Here is file '/tmp/Mod.pm', the module​:

================================================================

package Mod;

sub new {
  my ($pkg, $fh) = @​_;
  my $self = {FH => $fh};
  bless $self => $pkg;
}

sub readit {
  my $self = shift;
  local *FH = $self->{FH};
  my $str = <FH>;
  return $str;
}

1;

================================================================

When I run the program /tmp/t1, I expect it to print out
its own first line​:

  use Mod;

instead, it prints nothing.

Perl Info


Site configuration information for perl 5.00503:

Configured by mjd at Sun Jan 23 14:15:22 EST 2000.

Summary of my perl5 (5.0 patchlevel 5 subversion 3) configuration:
  Platform:
    osname=linux, osvers=2.2.12, archname=i586-linux
    uname='linux plover 2.2.12 #10 mon nov 1 17:02:09 est 1999 i586 unknown '
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=undef useperlio=undef d_sfio=undef
  Compiler:
    cc='cc', optimize='-O2', gccversion=egcs-2.90.29 980515 (egcs-1.0.3 release)
    cppflags='-Dbool=char -DHAS_BOOL -I/usr/local/include'
    ccflags ='-Dbool=char -DHAS_BOOL -I/usr/local/include'
    stdchar='char', d_stdstdio=define, usevfork=false
    intsize=4, longsize=4, ptrsize=4, doublesize=8
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    alignbytes=4, usemymalloc=n, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /shlib /lib /usr/lib
    libs=-lndbm -lgdbm -ldbm -ldb -ldl -lm -lc
    libc=/lib/libc.so.6, so=so, useshrplib=false, libperl=libperl.a
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic'
    cccdlflags='-fpic', lddlflags='-shared -L/usr/local/lib'

Locally applied patches:
    


@INC for perl 5.00503:
    /usr/lib/perl5/5.00503/i586-linux
    /usr/lib/perl5/5.00503
    /usr/lib/perl5/site_perl/5.005/i586-linux
    /usr/lib/perl5/site_perl/5.005
    .


Environment for perl 5.00503:
    HOME=/home/mjd
    LANG (unset)
    LANGUAGE (unset)
    LD_LIBRARY_PATH=/lib:/usr/lib:/usr/X11R6/lib
    LOGDIR (unset)
    PATH=/home/mjd/bin:/usr/local/bin:/bin:/usr/bin:/usr/X11/bin:/usr/games:/sbin:/usr/sbin:/usr/local/bin/X11:/usr/local/bin/mh:/data/mysql/bin:/home/mjd/TPI/bin:/usr/local/mysql/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash

@p5pRT
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p5pRT commented Jan 25, 2000

From @mjdominus

my $o = Mod->new(FH => \*TF);
my ($pkg, $fh) = @​_;

Gee, that was pretty stupid.

There really is a bug somewhere, but this doesn't demonstrate it.

I'll try again in the morning.

@p5pRT
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p5pRT commented Jan 26, 2000

From [Unknown Contact. See original ticket]

If you change your call from

  my $o = Mod->new(FH => \*TF);

to

  my $o = Mod->new(\*TF);

it works fine. It also works fine if you make it

  my $o = Mod->new(*TF);

I don't know why

  *X = *FH
and
  *X = \*FH

are the same, although I do know why

  *X = "FH"

is the same, because it actually means *X = *{"FH"}. Apparently,
*X = \*FH really means *X = *{ \*FH }. I'd say this breaks the
no implicit dereffing rule, but with stars, all bets are off.

Also, you wouldn't need the local *FH if you just called

  readline($self->{FH});

since readline() is a proper function not subject to the
sillinesses stopping < $self->{FH} > from working.

But I don't know if readline got fixed yet so it accepts
other than *FH. It should also accept anything <> does,
like FH and \*FH.

--tom

@p5pRT
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p5pRT commented Jul 13, 2003

From @rspier

chromatic says​:
Bug #2040 looks like it can be closed; the constructor was called
incorrectly in the test case, as Tom's comment points out.

@p5pRT
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p5pRT commented Jul 13, 2003

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

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