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 dimmed if the breakpoint is inactive, and outlined if that line has an action.
Click on the thick border between the code and watch expression panes to slide out the breakpoint list.
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
Child Processes
If the debugged program forks, it will pop up a dialog giving the option to "Open" a new debugger window, or "Detach" and allow it to run without stopping.
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.
- Get notification of untrapped exceptions, and stop at the exception point
- Stop execution when execution reaches a different point than a previous run
Pretty much what you would expect from any debugger.
Planned Features
- 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.