Re: Interactive scripting with DB

There's sure no better way to "become one" with a program, putting yourself "in its shoes" than running it inside an interactive debugger.

You might also like these tips and tricks;

Putting the line kill 2, $$ will cause the debugger to break at that point in the source (on Unix, anyway). This works by emulating pressing Ctrl+C (it's the interrupt signal). This is great for setting breakpoints deep down in your code.
If you ever turn strings into real functions via eval, then make sure to add a 'magic line number comment': eg,
```
sub some_auto_generated_function {
    my $self = shift;
# line 1 "some/preprocessedfile.foo"
    print $self->frop;
# line 7 "originalfile.pm"
}
[download]
```
If you do this, the emacs debugger will correctly step through the right source files. Sadly, though, the old perl5db.pl interactive debugger doesn't actually display the source properly.
Devel::ebug is a brand new debugger that doesn't have a lot of the limitations of the old debugger, in particular the segfaults, but instead brings a whole lot more new Storable related ones! Joy! But, anyway, this debugger is client/server with a very lightweight in-program "server", so you can debug remote programs. If you could write an emacs-compatible communication layer for it, you could bring this debugging to the "next level" of perl debuggers, which might include the debugger for Perl 6.

$h=$ENV{HOME};my@q=split/\n\n/,`cat $h/.quotes`;$s="$h/."
."signature";$t=`cat $s`;print$t,"\n",$q[rand($#q)],"\n";
[download]

Comment on Re: Interactive scripting with DB Select or Download Code

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Re^2: Interactive scripting with DB by tlm (Prior) on May 26, 2005 at 03:42 UTC
Putting the line kill 2, $$ will cause the debugger to break at that point in the source (on Unix, anyway). I had never seen that trick before. Cool. I have been using this one instead: `$DB::single = 1;` [download] That causes the debugger to enter "single-step" mode, which amounts to programmatically setting a breakpoint in the next executable line. This is particularly useful for causing the debugger to stop at places that happen before the first executable line, e.g.: `BEGIN { $DB::single = 1; } use Foo;` [download] The code above will enable stepping through the loading of 'Foo', which otherwise would happen before the place at which DB normally starts (i.e. the first executable line). I see that `kill 2, $$` works well for this too. One more trick for the bag. the lowliest monk	[reply] [d/l] [select]

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Re^2: Interactive scripting with DB
by tlm (Prior) on May 26, 2005 at 03:42 UTC

Putting the line kill 2, $$ will cause the debugger to break at that point in the source (on Unix, anyway).

I had never seen that trick before. Cool. I have been using this one instead:

$DB::single = 1;
[download]

before

BEGIN {
  $DB::single = 1;
}
use Foo;
[download]

kill 2, $$

the lowliest monk