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

[Richard Stallman]

    I don't think malloc is failing to allocate memory here, but something
    is causing x_catch_errors_unwind to be called without a matching call
    to x_catch_errors.

It does look that way.  But x_catch_errors_unwind was called from the
specpdl, and nothing ever puts it on the specpdl except x_catch_errors.
So something very very strange is happening.

I just looked at every call to x_catch_errors, and none of them seems
to be able to exit without a subsequent call to x_uncatch_errors which
should unwind it.

Can you examine the innermost specpdl bindings and see what
variables they bind?  Also, please examine a few slots
just beyond the specpdl_ptr, slots which were unwound recently.
What variables or unwind functions do they use?