using a source code debugger on vlc (and investigating a video

Gildas Bazin gbazin at
Sun Apr 29 10:37:12 CEST 2001

On Sun, 29 Apr 2001 04:47:58 Shane Harper wrote:
> Hi.
> I've been trying to use DDD v3.3 with GDB v5.0 to do source-level
> debugging
> of vlc. I've had very little success.
> I'd made the following changes to vlc/Makefile.opts:
> - changed "OPTIMS = 1" to "OPTIMS = 0"
> - changed "CFLAGS =" to "CFLAGS = -g"
I don't know if it makes any difference, but you can just run:
/configure --enable-debug --disable-optimizations

> At present when I try to start vlc from within DDD it runs for a short
> time
> before GDB reports that the program exited normally. (No interface or
> video
> output windows appear.)

Do you have SDL compiled in you version. I already reported a similar
problem where the probe function of the SDL audio plugin was crashing
everything when run inside GDB. If you want to check, you can recompile
the VLC without SDL support and see if you still have this crash.

> If I try to attach the debugger to a running vlc process I also
> experience
> problems, such as:
> - breakpoints (sometimes) don't work.
> - if I try to step through the code DDD can't show me the current line in
> the code after a function call using a function pointer.

Maybe, for some reasons, GDB cannot find some of the source files.
I already had the same problem: I was compiling everything and then
renaming the name of the VLC directory.
You can check what file GDB is trying to load with "strace".
Use "strace -e trace=open ddd" which will intercept all the open calls.

> I would appreciate any suggestions on how to run a debugger on vlc.
> The main problem I wish to investigate is why the XVideo (and X11) output
> seems to become slower the longer they run. I've made the following
> observations:
> - after I've noticed that vlc is skipping a lot of frames if I pause the
> video playback the video output thread can be using up to ~50% of my CPU
> resources (should be 0% when playback is paused).
> - changing to/from fullscreen mode seems to fix the problem (for a
> while).
> Does anyone have any ideas?
> (I'm running XFree86 v4.0.1a.)
> Thanks,
> Shane.

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