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From: Ilya Zakharevich <nospam-abuse@ilyaz.org>
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Subject: Re: Debugging Perl with Emacs / perldb
Date: Mon, 2 Aug 2010 21:42:25 +0000 (UTC)
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On 2010-08-01, William L Brown <bbrown@addtoit.com> wrote:
>   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...