lightsoff in gdb

[marja]

I don't yet manage to see how I can run lightsoff inside gdb. I only want to, because I want to learn more about how to get backtraces.
(It's a known bug https://bugs.mageia.org/show_bug.cgi?id=1078 and AL13N is already working on a patch)

Is the information I need in this line from lightsoff.strace:

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6447  execve("/usr/bin/env", ["/usr/bin/env", "seed", "/usr/share/gnome-games/lightsoff"...], [/* 80 vars */]) = 0

? 6447 was a child PID and the one that segfaulted. If this is the needed info, how do I use it with gdb?

Or was this information I need already in here:

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[marja@DenkBlok2 ~]$ lightsoff
/usr/bin/lightsoff: regel 4: 10694 Segmentatiefout         /usr/bin/env seed /usr/share/gnome-games/lightsoff/main.js
[marja@DenkBlok2 ~]$

BTW, I did install gnomes-games-debug

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[marja@DenkBlok2 ~]$ rpm -qf --qf "%{SOURCERPM}\n" /usr/bin/lightsoff | sed 's/-[^-]*-[^-]*$/-debug/'
gnome-games-debug
[marja@DenkBlok2 ~]$

[dubigrasu]

I would try something like:

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gdb lightsoff

or eventually in the same directory where the executable is located:

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gdb ./lightsoff

at the gdb prompt type:

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run

and after the segfault type:

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backtrace full

[marja]

Thx for answering, but I tried that before and that doesn't work:

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[marja@DenkBlok2 ~]$ gdb lightsoff
GNU gdb (GDB) 7.1-6.mga1 (Mageia release 1)
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-mageia-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
"/usr/bin/lightsoff": not in executable format: File format not recognized
(gdb) Quit


/usr/bin/lightsoff is a shellscript:

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#!/usr/bin/env sh

export LD_LIBRARY_PATH="/usr/lib64/gnome-games${LD_LIBRARY_PATH+:$LD_LIBRARY_PATH}"
/usr/bin/env seed /usr/share/gnome-games/lightsoff/main.js


and when you look in the folder /usr/share/gnome-games/lightsoff/ you see a lot of javascript files.

[doktor5000]

Well lightsoff, as you have experienced, is no good start to learn using GDB

BTW: If you experience errors, and want to provide the error messages to someone else
trying to help you, it's generally best to run every command prefixed by LC_ALL=C.
This sets C locale, so every output will not be localised in you systems current locale (language)
but in english, which is easier or more helpful to developers.

[marja]

2x thanks

I'm often not aware that it's better to stop trying something, so thanks for concluding that lightsoff isn't a good start to learn to use GDB. You're right!
And I wasn't aware that the code was partially in Dutch, I even had to edit another post twice today, because two seperate lines that I had written turned out to be in Dutch
I guess I was too much in a party mood because of Mageia's first birthday

[doktor5000]

No problem for me

[doktor5000]

Because i needed to use gdb myself now, actually for the first time, here's a good step-by-step guide to do this:
http://www.thegeekstuff.com/2010/03/deb ... using-gdb/
*hint* Look for the middle part of the headline of that page, see what i mean

[marja]

C Program

Apparently, the best way to start to know GDB, is try it on a program written in C

Here http://www.gnu.org/software/gdb/download/ANNOUNCEMENT I read GDB is a source-level debugger for Ada, C, C++, Objective-C,
Pascal and many other languages.

If it would be both possible and easy to use it on Java Script, I guess Java Script would be in the list.

[doktor5000]

Exactly.
Maybe you want to try valgrind?

[marja]

Maybe you want to try valgrind?

Good idea. Of course, I shouldn't start trying it with lightsoff, but I did anyway. At first I got this weird message

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valgrind Warning: Can't execute setuid/setgid executable:

that disappeared after I had changed the permissions for /usr/bin/lightsoff from 555 (that should have been enough permission, shouldn't it?) to 777. Later, when I changed them back to 555, the message didn't come back, Valgrind just kept working. It gives an enormous amount of output, though, so I couldn't scroll back to the beginning. Putting

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| less

behind the command string didn't work: the output disappeared the moment I tried to scroll through it.

And when I try

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valgrind -v --tool=memcheck --leak-check=yes --show-reachable=yes --num-callers=20 --track-fds=yes --trace-children=yes ./lightsoff | tee /home/marja/valgrindlightsoff.txt

or

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valgrind -v --tool=memcheck --leak-check=yes --show-reachable=yes --num-callers=20 --track-fds=yes --trace-children=yes ./lightsoff > /home/marja/valgrindlightsoff2.txt

I only create empty textfiles.

[marja]

But putting 2 before > works!

[marja]

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[marja@DenkBlok2 bin]$ valgrind -v --tool=memcheck --leak-check=yes --show-reachable=yes --num-callers=20 --track-fds=yes --trace-children=yes ./lightsoff 2> /home/marja/valgrindlightsoff3.txt
[marja@DenkBlok2 bin]$

Now the file isn't empty anymore, but contains 84,516 lines of text