Devel::hdb

A Perl graphical debugger that uses an HTTP REST interface

Usage

Start a program with the debugger

shell> perl -d:hdb yourprogram.pl
Debugger listening on http://127.0.0.1:8080/

Tell the debugger to use a different port

shell> perl -d:hdb=port:9876 yourprogram.pl
Debugger listening on http://127.0.0.1:9876

How to use it

Operation of the interface should be straightforward, though there are a few controls that may not be obvious.

Breakpoints and actions

Clicking on a line number will toggle an unconditional breakpoint for that line. Right-clicking on a line number will bring up a form to enter a breakpoint expression and action. When the expression evaluates true, the debugger will stop on that line.

A line number with a red circle is an unconditional breakpoint. A blue circle is a conditional breakpoint. The circle is outlined if that line has an action.

Watch Expressions

Click on the "+" to add a new watch expression.

Double-click on an existing expression to edit the expression.

For arrays, hashes and globs, click on the blue circle to collapse/expand it

Features

• Single step, step over, step out, continue and exit the debugged program
• Set breakpoints dynamically in the running program
• Inspect the current position at any level in the call stack
• Watch variables/expressions
• Get control when the process exits
• Hover over a variable to see its value. Works for all stack frames.

Pretty much what you would expect from any debugger.

Planned Features

• Get notification when the debugged process forks, with options to debug the child process, or allow it to continue
• Get notification of untrapped exceptions, and stop at the exception point
• Step into an arbitrary expression
• Restart execution at some prior execution point

Implementation

The debugger is split into three major parts.

• Devel::hdb::DB - Implements the debugger functions like DB::DB and DB::sub
• Devel::hdb::App - Implements the REST interface. It is a Plack app, and uses HTTP::Server::PSGI as the web server
• The user interface is HTML and JavaScript code that lives under Devel/hdb/html/. It makes requests to the REST interface.