https://github.com/mohawk2/devel-tracerun

Shows all the function calls and returns in a Perl program
https://github.com/mohawk2/devel-tracerun

debugging-tool perl

Last synced: about 1 month ago
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Shows all the function calls and returns in a Perl program

• Host: GitHub
• URL: https://github.com/mohawk2/devel-tracerun
• Owner: mohawk2
• Created: 2020-07-06T19:35:50.000Z (over 4 years ago)
• Default Branch: master
• Last Pushed: 2023-07-30T12:23:54.000Z (over 1 year ago)
• Last Synced: 2024-10-30T04:33:21.377Z (2 months ago)
• Topics: debugging-tool, perl
• Language: Perl
• Homepage: https://metacpan.org/pod/Devel::TraceRun
• Size: 12.7 KB
• Stars: 1
• Watchers: 2
• Forks: 2
• Open Issues: 2
• Metadata Files:
  • Readme: README.md
  • Changelog: Changes

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README

        
# NAME

Devel::TraceRun - Shows all the function calls and returns in a Perl program

# PROJECT STATUS

[![CPAN version](https://badge.fury.io/pl/Devel-TraceRun.svg)](https://metacpan.org/pod/Devel::TraceRun)

# SYNOPSIS

    $ perl -d -d:TraceRun -S yourscript

# DESCRIPTION

Figuring out a large system's workings is hard. Figuring out why it's

not working, and where it's going wrong, is even harder.

This tool produces an indented list of all function calls with parameters

(in a very very concise format) and return values (ditto). It aims to

minimise diffs between runs of a program that are doing the same thing,

so that differences stand out.

The output is on `STDOUT` currently. That may become overridable in

due course.

## Example

This code (from the test - `Thing::func` calls `Thing::func2` which

returns "2nd retval"):

    use Thing;

    my $f = sub { Thing::func() };

    Thing::func([2]); # void

    my @r = Thing::func([2]);

    my @r2 = $f->("very long string", 2, bless {}, 'Thing');

run with:

    perl -d -d:TraceRun script.pl

produces on perl 5.8 - 5.14 (output is slightly different from 5.16,

and again from 5.28):

    main::(script.pl:1)()

    return()

    Thing::func(ARRAY)

      Thing::func2()

      return()

    return()

    Thing::func(ARRAY)

      Thing::func2()

      return(2nd retval)

    return(2nd retval)

    main entry(very long ,2,Thing)

      Thing::func()

        Thing::func2()

        return(2nd retval)

      return(2nd retval)

    return(2nd retval)

Note that in void context, nothing is returned. Also note the `very long

string` is truncated to (currently) 10 characters, array- and hash-refs

are printed just as `ARRAY` and `HASH`, and objects as their classname.

There is currently no way to change what is printed. One thing that would

increase homogeneity across runs would be a way to specify for certain

function-names, which inputs or outputs to mask. Obvious examples where

this would help are functions that return the current time, or a random

number, or the port number of an incoming IP connection.

Another source of output variation is the change in Perl 5.18 to randomise

the order hash-keys are returned in. You can overcome this for tracing

purposes by setting the environment variable `PERL_HASH_SEED` to 0,

which also has the effect of setting `PERL_PERTURB_KEYS` to 0.

## How it works

As may be discerned from the command line, it uses Perl's debugging

functionality. However, unlike the normal use of that, it is entirely

non-interactive. Instead, it replaces `DB::DB` with a no-op, and uses

the `DB::sub` hook to report function entries and returns.

These reports are indented (currently hardcoded to two spaces), nested

according to stack depth. It is intended to be completely obvious what

everything means.

# SEE ALSO

[perldebguts](https://metacpan.org/pod/perldebguts)

# AUTHOR

Ed J

# COPYRIGHT AND LICENSE

This is free software; you can redistribute it and/or modify it under

the same terms as the Perl 5 programming language system itself.