in reply to Re^2: Splitting program into modules
in thread Splitting program into modules

So I've put together a very basic display of how the Devel::Trace::Subs works. Again, it's intrusive; it actually writes into the files you want to capture tracing info from (I wrote this software that another piece of software required, primarily out of sheer curiosity).

Here's the original Perl file we're working with (./

use warnings; use strict; three(5); sub three { return two(shift); } sub two { return one(_helper(shift)); } sub one { my $num = calc(shift); display($num); } sub calc { my $num = shift; return $num ** 3; } sub display { my $num = shift; print "$num\n"; } sub _helper { my $num = shift; return ++$num; }

When run, it produces this output:


Very basic. Now, install Devel::Trace::Subs, and from the command line, tell it to become traceable:

perl -MDevel::Trace::Subs=install_trace -e 'install_trace(file => "")' the file looks like this:

use warnings; use Devel::Trace::Subs qw(trace trace_dump); # injected by Devel::Trac +e::Subs use strict; three(5); sub three { trace() if $ENV{DTS_ENABLE}; # injected by Devel::Trace::Subs return two(shift); } sub two { trace() if $ENV{DTS_ENABLE}; # injected by Devel::Trace::Subs return one(_helper(shift)); } sub one { trace() if $ENV{DTS_ENABLE}; # injected by Devel::Trace::Subs my $num = calc(shift); display($num); } sub calc { trace() if $ENV{DTS_ENABLE}; # injected by Devel::Trace::Subs my $num = shift; return $num ** 3; } sub display { trace() if $ENV{DTS_ENABLE}; # injected by Devel::Trace::Subs my $num = shift; print "$num\n"; } sub _helper { trace() if $ENV{DTS_ENABLE}; # injected by Devel::Trace::Subs my $num = shift; return ++$num; }

I'd like to point out that the design for this software was to be used within modules not normal scripts, but I digress. In order to get the output from the tracing, you have to add a couple of things to your calling script (in this case, it's the original script itself). We'll pretend we're calling modules infected with the trace software here. Add the trace enabling flag, then after all of your calls have been made you want to get the trace info from, call the dump_trace() function::wq

$ENV{DTS_ENABLE} = 1; three(5); # this is the original call stack you're running trace_dump();

Now, you get the original output, but you also get the code flow and stack trace information:

216 Code flow: 1: main::three 2: main::two 3: main::_helper 4: main::one 5: main::calc 6: main::display Stack trace: in: main::three sub: - file: line: 7 package: main in: main::two sub: main::three file: line: 13 package: main in: main::_helper sub: main::two file: line: 17 package: main in: main::one sub: main::two file: line: 17 package: main in: main::calc sub: main::one file: line: 21 package: main in: main::display sub: main::one file: line: 22 package: main

You can opt via parameters to trace_dump to display just the code flow or the stack trace or both (as is the default as shown above), in text or HTML output formats.

This is a *very* basic example of how I've used this software. Again, we're using it in a single file here. Normally I'd have a test script using external modules, so the command to return your original code is this:

perl -MDevel::Trace::Subs=remove_trace -e 'remove_trace(file => "")'

...which returns the script back to default, except for the manual lines (which wouldn't normally be in an original .pl file). Delete these lines manually:

$ENV{DTS_ENABLE} = 1; trace_dump();

I'll try to put together a much better example of how I really use it in the coming days.

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Re^4: Splitting program into modules
by LanX (Sage) on Nov 14, 2018 at 13:44 UTC
    > Again, it's intrusive;

    I wonder why you prefer it that way, there are at least two alternatives

    • running under the debugger and activating the trace option
    • inspecting the stash of the included packages and dynamically monkey patching the subs with tracing wrappers.

    Am I missing something?

    Cheers Rolf
    (addicted to the Perl Programming Language :)
    Wikisyntax for the Monastery FootballPerl is like chess, only without the dice

      I definitely don't prefer it this way. This was a project I started many, many years ago actually. It was one of the very first projects I ever thought of when I started writing Perl, and it took many years to put together. It was more a "can I do this" thing :)

      As a matter of fact, another project I went on for the sake of learning how is monkey patching on the fly with my Mock::Sub and Wrap::Sub, so updating Devel::Trace::Subs is something I definitely could do to remove the actual writing to files. I'll create myself an issue so I don't forget to do this someday.