bug#1125: 23.0.60; Occasional hangs in redisplay

[Chong Yidong]

> In Ubuntu Intrepid, I have an "emacs --daemon" instance that I
> occasionally connect to via "emacsclient -t". The daemon watches log
> files etc. After a few days, the daemon consistently hangs, taking
> lots of CPU time, and I cannot connect to it any more. When I attach
> gdb to it, the backtrace always looks as follows. The hanged instance
> is still running, and I can give more information about any values if
> needed.

> 0x08072479 in calc_pixel_width_or_height (res=0xbfaac058, it=0xbfaad794, 
>     prop=568, font=0x0, width_p=1, align_to=0xbfaac064) at xdisp.c:19302
> 19302         return OK_PIXELS (XFLOATINT (prop) * base_unit);
> (gdb) bt
> #0  0x08072479 in calc_pixel_width_or_height (res=0xbfaac058, it=0xbfaad794, 
>     prop=568, font=0x0, width_p=1, align_to=0xbfaac064) at xdisp.c:19302

I don't see how `return OK_PIXELS (XFLOATINT (prop) * base_unit);' could
possibly hang.  Maybe the backtrace is screwy because of compiler
optimizations.

Could you recompile without optimizations (CFLAGS="-g"), try to
reproduce the hang, and get another backtrace?

Thanks.