Jack Shirazi > DumpStack-1.1 > Devel::DumpStack



Annotate this POD

View/Report Bugs


Devel::DumpStack - Access to the current stack of subroutine calls, and dumping the stack in a readable form. See also sigtrap.



    use Devel::DumpStack ...;
    dump_stack($depth,$indent,$print_level); #Prints to STDERR
    $stack = stack_as_string($depth,$indent,$print_level);
    $call_string = call_at_depth($depth,$print_level);
    ($args,$pack,$file,$line,$sub,$has_args,$wantarray) = caller2($depth);
    $printable_arg = printable_arg($arg,$print_level);
    dump_on_die($print_level); #dumps stack to STDERR on a 'die'


Provides functions to access and dump the current stack of subroutine calls.

Functions Available:

(Note that only 'dump_stack' is exported by default.)

dump_stack(DEPTH, INDENT)

This prints the current functions stack to STDERR. DEPTH is the depth of the stack to print from - equivalent to the depth in caller(). Note that you can use negative numbers for DEPTH if you want to include the dump_stack call and calls under it on the stack print.

PRINT_LEVEL is 0, 1 or 2, depending on the level of detail you want printed out for arguments. See Devel::CallerItem.

The lines printed are in one of the appropriate formats:

    $ = func(args) called from FILE line LINE;
    $ = &func called from FILE line LINE;
    @ = func(args) called from FILE line LINE;
    @ = &func called from FILE line LINE;

giving the context (scalar - $, array - @) and whether it was called with arguments or without (&).

INDENT is a string which is appended to the beginning of each line printed out.

stack_as_string(DEPTH, INDENT, PRINT_LEVEL)
stack_as_string(DEPTH, INDENT)

Exactly as dump_stack, but instead of printing to STDERR, returns the stack as a string.


Calling this function inserts a handler for any 'die' calls, so that when a 'die' is called, the current stack is first printed to STDERR before exiting the process. You probably don't want to do this if you are die'ing in an eval. PRINT_LEVEL is as above.

printable_arg(ANYTHING, PRINT_LEVEL)

Renders its argument printable. PRINT_LEVEL is as above.


Returns exactly what caller returns, except that the reference to the argument array for the call at that depth is prepended to the array - i.e. the first element of the returned array is a reference to the argument array of the function called at depth DEPTH, and the subsequent elements are the elements returned by caller, in the same order. Returns undef if there is no call at depth DEPTH.

call_at_depth(DEPTH, PRINT_LEVEL)

Returns a string in the format as given in dump_stack above, but just for the single function call at the given DEPTH. PRINT_LEVEL is as above.


The following is a simple example, and can be executed using perl -x Devel/DumpStack.pm


    use Devel::DumpStack qw(dump_stack);
    $c = bless [], A;
    $d = [$c];
    $c->[0] = $d;
    sub a { dump_stack(0,'    ',1); print STDERR "\n";}
    sub c { $scalar_context =  a(@_)}
    sub b { c([44,[66,{'q','hi'},\$a],$c])}

    @arr_context = &b;



Jack Shirazi

  Copyright (c) 1995 Jack Shirazi. All rights reserved.
  This program is free software; you can redistribute it and/or
  modify it under the same terms as Perl itself.


Version 1.1, 31st July - JS

Extracted out the Devel::CallerItem module, and added various functions and print level extensions. NOTE that the module produces a slightly different effect from version 1.0 - the DEPTH parameters are now all set to work as if the function being called is a replacement for caller - this means that the depths in version 1.0 are 1 or 2 different from the versions in 1.1. I felt the change was worth it - now all calls with DEPTH are consistent.

Base version, 1.0, 24th April - only posted to perl-porters - JS.

syntax highlighting: