[ID 20000403.026] memory leak, closures

Reply-To: sam@internal.schools.net.au

This is a bug report for perl from sam@internal.schools.net.au,
generated with the help of perlbug 1.26 running under perl 5.00503.

How to toast your memory with perl closures (minimalistic version):

my $m1;

while(1) {
    sub {
	sub {
	    return;
	    $m1
	}
    }
}

This GC misbehaviour seems to occur when closures
(i.e. anon subroutines referencing my variables from outside)
are nested two levels deep.  Here's another example:

my $m1;

while(1) {
    sub {
	my $m2 = $m1;
	my $m3 = $::c++;
	sub {
	    return;
	    $m3
	}
    }
}

Note, here the links outward are very tenuous!

Please help! or can you explain?  I can guess there is some internal
circular referencing going on.  I *care* about this, because it's
stuffing up the interesting networking project that I'm working on!

Thanks,

Sam Watkins

---
Site configuration information for perl 5.00503:

Configured by torin at Tue Feb 29 07:28:09 PST 2000.

Summary of my perl5 (5.0 patchlevel 5 subversion 3) configuration:
  Platform:
    osname=linux, osvers=2.2.14, archname=i386-linux
    uname='linux perv 2.2.14 #1 sat jan 15 20:48:59 pst 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 20000220 (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:
    /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/sam
    LANG=C
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=.:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/X11R6/bin:/home/sam/bin:/usr/local/jdk118/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash

---
sam@internal.schools.net.au
http://www.internal.schools.net.au/

• [ID 20000403.026] memory leak, closures by sam