Strange crash

Dmitry Timoshkov dmitry at
Tue Apr 17 22:54:37 CDT 2001

"Rein Klazes" <rklazes at> wrote:

> > Exception occurs when pen->logpen.lopnWidth.x = 0 and dc->xformWorld2Vport.eM11 = 0.0
> > It's very strange. Attached patch helps to eliminate crash. But I don't understand
> > where the source of problem.
> | 0x40897fde (X11DRV_PEN_SelectObject+0x8e [pen.c:69]): fldcw 0xfffffffe(%edx)
> This instruction loads the control status word with a new value. Bit 5
> of the CW (0x20) ,PM Precision Mask , is the mask bit for this
> exception.
> Find out how this bit has become zero (disassembly of the instructions
> before the crash). If I put a breakpoint on the instruction above, the
> CW is loaded with 0x37f: all FP exceptions are off.

I have attached full assembly listing of graphics/x11drv/pen.c produced by gcc.
I removed -g option to reduce the output size and added -S -fverbose-asm.
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