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[ID 20000927.002] map & objects not destroyed when leaving scope

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From:
pimlott
Date:
September 27, 2000 21:55
Subject:
[ID 20000927.002] map & objects not destroyed when leaving scope
Message ID:
m13eW5a-000SEmC@nolfolan.idiomtech.com
This is a bug report for perl from pimlott@idiomtech.com,
generated with the help of perlbug 1.26 running under perl 5.00503.


-----------------------------------------------------------------
[Please enter your report here]

I'm not positive this is a bug, but it's surprising and it smells like an
over-eager optimization.  Say I have

    sub foo { my $foo = new Foo; return; }
    @res = map { foo() } 1..2;

Then the Foo instances, which go out of scope when foo returns, are not
destroyed until after the map finishes.  However, with a small change,

    @res = map { foo(); 1 } 1..2;

the instances are destroyed as expected.  The following complete example
demonstrates.

    package Foo;

    sub new { $count++; print "$count Foo objects\n"; bless {} => 'Foo'; }
    sub DESTROY { $count--; print "$count Foo objects\n"; }

    package main;

    sub foo { my $foo = new Foo; return; }
    @res = map { foo() } 1..2;

This prints

    1 Foo objects
    2 Foo objects
    1 Foo objects
    0 Foo objects

but when I make the change mentioned above, it prints

    1 Foo objects
    0 Foo objects
    1 Foo objects
    0 Foo objects

Andrew

[Please do not change anything below this line]
-----------------------------------------------------------------

---
Site configuration information for perl 5.00503:

Configured by drow at Sun Apr 30 12:07:23 EDT 2000.

Summary of my perl5 (5.0 patchlevel 5 subversion 3) configuration:
  Platform:
    osname=linux, osvers=2.2.15pre14, archname=i386-linux
    uname='linux them 2.2.15pre14 #2 smp mon mar 13 14:29:00 est 2000 i686 unknown '
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=undef useperlio=undef d_sfio=undef
  Compiler:
    cc='cc', optimize='-O2 ', gccversion=2.95.2 20000313 (Debian GNU/Linux)
    cppflags='-Dbool=char -DHAS_BOOL -D_REENTRANT -DDEBIAN -I/usr/local/include'
    ccflags ='-Dbool=char -DHAS_BOOL -D_REENTRANT -DDEBIAN -I/usr/local/include'
    stdchar='char', d_stdstdio=undef, 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 /lib /usr/lib
    libs=-lnsl -lndbm -lgdbm -ldbm -ldb -ldl -lm -lc -lposix -lcrypt
    libc=, 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:
    /home/pimlott/idiom/perl
    /usr/lib/perl5/5.005/i386-linux
    /usr/lib/perl5/5.005
    /usr/local/lib/site_perl/i386-linux
    /usr/local/lib/site_perl
    /usr/lib/perl5
    .

---
Environment for perl 5.00503:
    HOME=/home/pimlott
    LANG (unset)
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/pimlott/bin:/usr/local/atria/bin:/usr/sbin:/sbin:/home/pimlott/bin:/usr/local/atria/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games
    PERL5LIB=/home/pimlott/idiom/perl
    PERL_BADLANG (unset)
    SHELL=/usr/bin/zsh


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