mesa and sproc

Dave Semeraro semeraro at
Tue Jan 25 12:01:24 EST 2000

I recently posted a question about a problem I was having using threads and
Mesa off screen rendering. The problem appeared when I tried to use the
off screen rendering with a vtkMesaRenderWindow and sproc for threading. The
problem didnt occur when using pthreads. The actual error was a core dump
when calling the malloc in vtkOSMesaCreateWindow. I traced the problem down
with a debugger and found the problem to be a previous call to free in
vtkOSMesaDestroyWindow. Initially the pointer passed to this routine was
not initialized to anything and the free call caused subsequent malloc calls
to fail. I fixed the problem by initializing the pointer to null in the
constructor (this->OffScreenWindow = NULL;) and testing for NULL pointer in
the vtkOSMesaDestroyWindow function before freeing the memory. All these
were made in the vtkMesaRenderWindow class. I am building on an SGI Octane 
running irix 6.5. I am using a nightly release dated December 7, 1999. The
MesaRenderWindow class is probably different by now. I hope this helps
someone out there anyway. 


Dave Semeraro

Dave Semeraro Ph.D.
Site Scientific Visualization Lead
ASC MSRC Wright Patterson Airforce Base

Visualization and Virtual Environments Group
NCSA University of Illinois
605 E. Springfield Ave.
Champaign, IL 61820
semeraro at
(217) 244-1852

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