SEGV mythfrontend while attempting edit recording

[Stuart Auchterlonie]

Managed to crash the frontend while attempting to edit an existing recording.

BT is attached.

[Stuart Auchterlonie]

backtrace of frontend death.

[danielk]

(In [7583]) References #466.

This cleans up the function where the crash actually a happened a bit. But I don't know what actually caused the crash, so this just makes the backtrace look better.

A new backtrace is needed of course.

But it would also be useful to know what edit keys were actually hit and what the aspect ratio of the video and screen were, and if there was a letterbox mode in effect. And what the resolution of the video and screen were.

[Stuart Auchterlonie]

Initial testing doing exactly what I was doing before on the exact same recording it no longer crashed. But the frontend log did generate quite a lot of

[mpeg2video @ 0xb75a8270]warning: first frame is no keyframe

and at roughly the point where it was crashing it also showed

[dvbsub @ 0xb75a8270]Junk in packet
[dvbsub @ 0xb75a8270]Invalid object location!

The action I was performing at the time was hit 'e' for edit.

The most relevant part of the earlier backtrace I found was

​http://svn.mythtv.org/trac/attachment/ticket/466/frontend-bt.txt#L29

this shows that drawwidth had gone negative. Debugging showed me at the time that the xstart was exceeding the width of the surface.

From osdtypes.cpp, rev 7582, line 945-946

    if (drawwidth + xstart > surface->width)
        drawwidth = surface->width - xstart - 1;

This calculation caused drawwidth to go negative when xstart > surface->width which memcpy didn't like very much.

Looks like you have reworked the relevant area of the code to prevent this condition and therefore the crash.