finding source of segfault
ajax at nwnk.net
Wed Jun 14 08:02:27 PDT 2006
On Wednesday 14 June 2006 01:34, Drew Parsons wrote:
> I'm writing now on the off-chance that someone might recognise the
> signature of the segfault and be able to pinpoint which lib needs to be
> upgraded to X11R7.1 (or beyond). The backtrace looks like:
> #0 0x00000000 in ?? ()
> #1 0x080bc2ee in compCreateWindow (pWin=0x875e6e8) at compwindow.c:600
This sort of signature typically means you attempted to call through a
function pointer that was set to NULL. compCreateWindow calls through three
of the screen's function pointer chains: CreateWindow, GetWindowPixmap, and
Line 600 of compwindow.c calls both the GetWindowPixmap and SetWindowPixmap
chains. These are normally always provided by fb, but while Xprint's raster
and pcl backends wrap fb, the postscript backend does not, and does not
itself provide implementations for those chains. Woo!
Right now those chains are only ever called from the Damage and Composite
extensions, so the minimal hack might be to just always disable those in
Xprt; I had thought this was done already though. The better solution might
be to add stub implementations to the postscript backend and see what breaks.
Since the ps backend clearly believes it can implement the world without
using fb, it might be fine to just have those calls no-op.
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