perlman.pl only works in the debugger under cygwin

diamond has asked for the wisdom of the Perl Monks concerning the following question:

The book Advanced Perl Programming by Sriram Srinivasan contains a perl script to display the content of man pages in a TK window. When attempting to run the script under the current cygwin, using its version of perl, TK, X, etc. I get a stack dump:

$ perlman.pl
Scouting man directories
Starting UI ...Tk::Error: Can't set -activebackground to `undef' for T
+k::Menu=HASH(0x103a7ad0): Cannot use undef value for object of type '
+border' at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/Tk/Configure.p
+m line 46.
 at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/Tk/Derived.pm line 294
 Tk callback for .
 Tk callback for .frame
 Tk::Derived::configure at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin
+/Tk/Derived.pm line 306
 Tk::Widget::new at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/Tk/Wid
+get.pm line 205
 Tk::Widget::__ANON__ at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/T
+k/Widget.pm line 256
 Tk::Menubutton::menu at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/T
+k/Menubutton.pm line 348
 Tk::Menubutton::separator at /usr/lib/perl5/vendor_perl/5.10/i686-cyg
+win/Tk/Menubutton.pm line 358
 main::create_ui at script/perlman.pl line 105
Can't set -activebackground to `undef' for Tk::Menu=HASH(0x103a7ad0): 
+Cannot use undef value for object of type 'border' at /usr/lib/perl5/
+vendor_perl/5.10/i686-cygwin/Tk/Configure.pm line 46.
 at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/Tk/Derived.pm line 294

 at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/Tk/Derived.pm line 306
[download]

However, when invoked through the debugger the script runs just fine:

$ perl -d perlman.pl

Loading DB routines from perl5db.pl version 1.3
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(perlman.pl:8):    print STDERR "Scouting man directories\n";
  DB<1> c
Scouting man directories
Starting UI ...Done
[download]

...after which the Perlman window appears.

Any ideas?

Comment on perlman.pl only works in the debugger under cygwin Select or Download Code

Replies are listed 'Best First'.
Re: perlman.pl only works in the debugger under cygwin by Anonymous Monk on Feb 27, 2009 at 16:03 UTC
Try PerlMan - Perl/Tk based pod pick/view, Tk::Pod	[reply]
Re^2: perlman.pl only works in the debugger under cygwin by diamond (Acolyte) on Feb 27, 2009 at 18:09 UTC
Thanks for the reply. I was actually wondering why the perlman.pl script only works when being debugged rather than looking for a suggestion for an alternate, perl-based, GUI man page viewer.	[reply]
Re: perlman.pl only works in the debugger under cygwin by webfiend (Vicar) on Feb 27, 2009 at 18:03 UTC
This looks like some fairly crusty old code. You probably are better off with the suggestion of using something else. Nevertheless, I am curious. Do you get any information running this script with warnings enabled?	[reply]
Re^2: perlman.pl only works in the debugger under cygwin by diamond (Acolyte) on Feb 27, 2009 at 21:42 UTC
There is only one warning: `"my" variable $section masks earlier declaration in same scope at perl +man.pl line 179. Scouting man directories Starting UI ...Use of uninitialized value $id in hash element at /usr/ +lib/perl5/vendor_perl/5.10/i686-cygwin/Tk/After.pm line 39.` [download] etc. Removing the second my declaration does not change the result (nor should it, looking at the code). I am puzzled as to how the debugger "fixes" the code. The implication from error messages is that an undefined value is being used where it is not permitted; how can the debugger fix that? In fact, it shouldn't. The reason I even tried the script in the debugger was to see where the problem was and to try to fix it.	[reply] [d/l]
Re: perlman.pl only works in the debugger under cygwin by JadeNB (Chaplain) on Mar 01, 2009 at 02:24 UTC
It seems to be the `create_ui` call that's failing, and the only variable there that isn't set explicitly (like `$match_type` and `$ignore_case`) or wrapped (like `'-label' => "($section_name)"` on line 153) is the `$section_name` in the arrayref passed to `command` on line 154. Could you add some diagnostics before and after to see if it's this call that's the problem? (I'm a little suspicious of that call anyway, since the author seems to think that a `my $var; for $var (@array) {}` declaration makes sense, whereas in fact the `my $var` has no effect on the `for` code—not even shadowing any external occurrence of `$var`. (Also, I don't see where the hash `%sections` is initialised.))	[reply] [d/l] [select]
Re: perlman.pl only works in the debugger under cygwin by lamprecht (Friar) on Mar 01, 2009 at 15:21 UTC
Hi, I don't have Tk under cygwin to test, but what happens if you override your default activebackground like so: line90 ++ `sub create_ui { my $top = MainWindow->new(); $top->optionAdd('*activeBackground' => 'red');# or sth. # MENU STUFF` [download] Regards, Christoph	[reply] [d/l]


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