in reply to Re^3: memory leak when using tail recursion?
in thread memory leak when using tail recursion?

ikegami,
Very interesting. I am up over 200MB in 30 seconds if I use the block form of if. If I use the post modifier form of if, it stays fixed at 2MB.

Cheers - L~R

  • Comment on Re^4: memory leak when using tail recursion?

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Re^5: memory leak when using tail recursion?
by ikegami (Patriarch) on Feb 14, 2007 at 00:20 UTC
    The if statememt creates a stack frame, while the statement modifiers do not. goto must reuse the sub's frame when possible. It apparently can't when the sub's frame isn't the topmost frame on the stack.
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      That's interesting. The following code doesn't leak though: 
      #!/usr/bin/perl
use strict;
use warnings;

bar();

sub bar {
    my $result = foo();
    if ( $result ) {
        goto &bar;
    }
    return;
}

my $i = 0;
sub foo {
    return $i++ < 1_000_000_000;
}

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      Wouldn't this leak if the if-statement was creating a stack frame as you said?
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        Intersting! I'm even willing to dive into the guts to see if I can find the answer, but I can't tonight.
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        I confused "scope" with "stack frame". While if creates a lexical scope, no stack frame is created.

        Because if creates a lexical scope, the following dies: 

        >perl -e "use strict; if (my $x = foo()) { } print $x;
Global symbol "$x" requires explicit package name at -e line 1.
Execution of -e aborted due to compilation errors.

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        If if created a stack frame, the following would print abcde instead of abced: 

        sub P1::DESTROY { print 'd'; }
sub P2::DESTROY { print 'c'; }
{
   print('a');
   if (my $x = bless({}, 'P1')) {
      my $y = bless({}, 'P2');
      print('b');
   }
   print('e');
}
print("\n");

        [download]

        Anyway, I didn't find an answer to your question.

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