NAME¶

DB - programmatic interface to the Perl debugging API

SYNOPSIS¶

    package CLIENT;
    use DB;
    @ISA = qw(DB);
    # these (inherited) methods can be called by the client
    CLIENT->register()      # register a client package name
    CLIENT->done()          # de-register from the debugging API
    CLIENT->skippkg('hide::hide')  # ask DB not to stop in this package
    CLIENT->cont([WHERE])       # run some more (until BREAK or another breakpt)
    CLIENT->step()              # single step
    CLIENT->next()              # step over
    CLIENT->ret()               # return from current subroutine
    CLIENT->backtrace()         # return the call stack description
    CLIENT->ready()             # call when client setup is done
    CLIENT->trace_toggle()      # toggle subroutine call trace mode
    CLIENT->subs([SUBS])        # return subroutine information
    CLIENT->files()             # return list of all files known to DB
    CLIENT->lines()             # return lines in currently loaded file
    CLIENT->loadfile(FILE,LINE) # load a file and let other clients know
    CLIENT->lineevents()        # return info on lines with actions
    CLIENT->set_break([WHERE],[COND])
    CLIENT->set_tbreak([WHERE])
    CLIENT->clr_breaks([LIST])
    CLIENT->set_action(WHERE,ACTION)
    CLIENT->clr_actions([LIST])
    CLIENT->evalcode(STRING)  # eval STRING in executing code's context
    CLIENT->prestop([STRING]) # execute in code context before stopping
    CLIENT->poststop([STRING])# execute in code context before resuming
    # These methods will be called at the appropriate times.
    # Stub versions provided do nothing.
    # None of these can block.
    CLIENT->init()          # called when debug API inits itself
    CLIENT->stop(FILE,LINE) # when execution stops
    CLIENT->idle()          # while stopped (can be a client event loop)
    CLIENT->cleanup()       # just before exit
    CLIENT->output(LIST)    # called to print any output that API must show

DESCRIPTION¶

Perl debug information is frequently required not just by debuggers, but also by modules that need some "special" information to do their job properly, like profilers.

This module abstracts and provides all of the hooks into Perl internal debugging functionality, so that various implementations of Perl debuggers (or packages that want to simply get at the "privileged" debugging data) can all benefit from the development of this common code. Currently used by Swat, the perl/Tk GUI debugger.

Note that multiple "front-ends" can latch into this debugging API simultaneously. This is intended to facilitate things like debugging with a command line and GUI at the same time, debugging debuggers etc. [Sounds nice, but this needs some serious support -- GSAR]

In particular, this API does not provide the following functions:

• data display
• command processing
• command alias management
• user interface (tty or graphical)

These are intended to be services performed by the clients of this API.

This module attempts to be squeaky clean w.r.t "use strict;" and when warnings are enabled.

BUGS¶

The interface defined by this module is missing some of the later additions to perl's debugging functionality. As such, this interface should be considered highly experimental and subject to change.

AUTHOR¶

Gurusamy Sarathy gsar@activestate.com

This code heavily adapted from an early version of perl5db.pl attributable to Larry Wall and the Perl Porters.