Debugging Perl with Emacs / perldb
William L Brown
With "perl -d" on the command line, the standard perl debugger, I
see the code inside of a perl eval as I execute it. Eval'ed code is
code that is created from scratch, outside of a code file and which then
becomes part of your program. Inside if emacs, depending upon my
environment, I either see:
Nothing but an indicator of what line I am running with no view of the
line:
(eval 6)[/home/bbrown/newTmp/emacsDebugTests/foo.pl:8]:7:0
or a new buffer pops up in emacs, with name (eval x), with absolutely
no text inside of it.
How do I fix this issue? Who can I ask? The issue seems to fit
snuggly between Emacs experts and Perl experts.
Thanks very much for your time.
Bill
ps. I included some sample code just to show you how I typically
use eval. A transcript of my "perl -d" session, where I see at
least one line of the eval at a time, follows.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
my $code = "
my (\$foo, \$bar) = \@_;
print \$foo;
print \$bar;
return \$bar;
";
my $subroutine = "sub { $code }";
my $proc = eval $subroutine;
my $baz = "1\n";
my $bat = "2\n";
my $output = eval {no strict "refs"; $proc->($baz, $bat); };
print $output;
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
bbrown@parvathi:~/newTmp/emacsDebugTests$ perl -d foo.pl
Loading DB routines from perl5db.pl version 1.32
Editor support available.
Enter h or `h h' for help, or `man perldebug' for more help.
main::(foo.pl:1): my $code = "
main::(foo.pl:2): my (\$foo, \$bar) = \@_;
main::(foo.pl:3): print \$foo;
main::(foo.pl:4): print \$bar;
main::(foo.pl:5): return \$bar;
main::(foo.pl:6): ";
DB<1> n
main::(foo.pl:7): my $subroutine = "sub { $code }";
DB<1> n
main::(foo.pl:8): my $proc = eval $subroutine;
DB<1> n
main::((eval 6)[foo.pl:8]:7): ;
DB<1> n
main::(foo.pl:9): my $baz = "1\n";
DB<1> n
main::(foo.pl:10): my $bat = "2\n";
DB<1> n
main::(foo.pl:11): my $output = eval {no strict "refs";
$proc->($baz,
$bat); };
DB<1> s
main::(foo.pl:11): my $output = eval {no strict "refs";
$proc->($baz,
$bat); };
DB<1> s
main::CODE(0x8626a50)((eval 6)[foo.pl:8]:2):
2: my ($foo, $bar) = @_; <- I can see the source!!!
DB<1> n
main::CODE(0x8626a50)((eval 6)[foo.pl:8]:3):
3: print $foo;
DB<1> n
1
main::CODE(0x8626a50)((eval 6)[foo.pl:8]:4):
4: print $bar;
DB<1> n
2
main::CODE(0x8626a50)((eval 6)[foo.pl:8]:5):
5: return $bar;
DB<1> n
main::(foo.pl:12): print $output;
DB<1> n
2
Debugged program terminated. Use q to quit or R to restart,
use o inhibit_exit to avoid stopping after program termination,
h q, h R or h o to get additional info.
DB<1>
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
--
William L. Brown
______________________________________
bbr...@addtoit.com
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______________________________________
Ilya Zakharevich
> Nothing but an indicator of what line I am running with no view of the
> line:
> (eval 6)[/home/bbrown/newTmp/emacsDebugTests/foo.pl:8]:7:0
From this info, an external program cannot deduce what happens. We
know that we are on 7th line of $foo, and that
eval $foo
was called on the 8th line of
/home/bbrown/newTmp/emacsDebugTests/foo.pl. But how would Emacs know
what is the contents of $foo?
Perl's debugger is not READING scripts to find "the code on line 6 of
bar.pl"; Perl (in debugging mode) just keeps the array of lines SEEN
by the compiler (an array per each file). For Perl, this $foo becomes
just another "input file", so it has the associated array, and Perl's
debugger can inspect what is on 7th line of this $foo.
Emacs' debugging, on the other hand, is based on reading "raw files"
from the filesystem. I see no easy way to communicate the needed info by
IPC... [*]
Hope this helps,
Ilya
P.S. [*] Of course, one can extract the relevant arrays from Perl
(using, e.g., the `l' operator). But this would require some
extra parsing...
Joseph Brenner
Gary <help-gn...@garydjones.name> writes:
> William L Brown wrote:
>> With "perl -d" on the command line, the standard perl debugger, I
>> see the code inside of a perl eval as I execute it. Eval'ed code is
>> code that is created from scratch, outside of a code file and which then
>> becomes part of your program.
>
> Have you tried http://www.khngai.com/emacs/perl.php for example?
What are you talking about? There are three fairly basic subjects
discussed there, and none look like they have any bearing on what
William is asking about.