Re: Ediff frequently crashes emacs.

[Richard Stallman]

Please follow the advice in etc/DEBUG for what to do when Emacs is
looping.

Meanwhile, I do see something in the backtrace:

    #4  0x402037e8 in XSync () from /usr/X11R6/lib/libX11.so.6
    #5  0x080c76da in x_catch_errors_unwind (old_val=157977501) at xterm.c:7622
    #6  0x08141bd7 in unbind_to (count=26, value=137321169) at eval.c:3116

This is handling an error.  If you put abreakpoint at Fsignal and
continue, you can see what causes the error.