Bug#405803: [Mesa3d-dev] Blender extrusion makes X SIGSEGV

[Brian Paul]

Cyril Brulebois wrote:
> Hi,
> 
> we received in the Debian BTS a bugreport about Blender making Xorg
> SIGSEGV, and by having a closer look at xorg-server (1.1.1), it looks
> like there's something wrong with the initialization of a span
> structure. Following Michel Dänzer's suggestion, I'm forwarding this
> report to you.
> 
> By checking the headers, we've got:
>   GLuint  z[MAX_WIDTH];                      // s_context.h
> 
> And:
>   #define MAX_WIDTH 4096                     // config.h
> 
> There are also some asserts:
>   ASSERT(span->end <= MAX_WIDTH);            // s_span.c
> 
> But during the initialization (s_linetemp.h and s_context.h), end is set
> to numPixels, which is MAX2(dx, dy), with dx=1 and dy=10398.

Something's fishy there.  The line should have been clipped to the 
window and I doubt the window is 10398 pixels tall.


> Then, in the direct_depth_test_pixels16 function (s_depth.c), the SEGV
> occurs when z[i] is read, with i=4096.
> 
> This happens on Linux as well as on GNU/kFreeBSD, with the nv driver
> (and no DRI).
> 
> You might want to refer to the original bugreport in the Debian BTS[1],
> to the last message I wrote there[2], and to a backtrace[3].
> 
>  1. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=405803
>  2. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=405803;msg=33
>  3. http://kibi.sysif.net/pub/bugreports/blender-sid-kfreebsd.trace
> 
> I'm also willing to test patches if you want me to.

I'm trying to reproduce this here, but I can't follow the steps to 
reproduce the bug:

> With a new blender file:
> 
> - NUM1>>Add>>Cube
> - AKEY   (unselect all elements)
> - BKEY   (block selection)
> - select the bottom (or top) vertices with the mouse LMB
> - EKEY>>Region  (extrude region)

How do you "select the bottom (or top) vertices"?  I'd expect that I 
should shift-click on the two verts or use a selection box, but that 
doesn't work.  I also don't see how to do an extrusion.

I'm not a blender user so I need everything spelled out in detail.

Also, how do I run blender in a normal window so I can work in a 
shell/gdb at the same time?

-Brian