Re: SEGV in x_catch_errors_unwind (x86_64-unknown-linux-gnu)

[Chong Yidong]

> However, as I was looking at the following loop unbind_to in eval.c,
> it occurred to me that one way the x_catch_errors_unwind function
> could be called twice in succession would be if specpdl_ptr is
> incremented by the addition of additional bindings while the loop is
> running (by some other code that is misbehaving while manipulating the
> specpdl array).

Yes, that's the problem.  Putting that loop inside a BLOCK_INPUT
prevents the crash.