bug#38748: 28.0.50; crash on MacOS 10.15.2

[Robert Pluim]

>>>>> On Thu, 9 Jan 2020 14:16:54 +0000, Pip Cet <pipcet@gmail.com> said:

    Pip> On Thu, Jan 9, 2020 at 1:51 PM Andrii Kolomoiets 
<andreyk.mad@gmail.com> wrote:
    >> Here is the '~/emacs-crash.el' content:
    >> (make-frame `((parent-frame . ,(window-frame))))
    >> (make-frame `((parent-frame . ,(window-frame))))
    >> (make-frame `((parent-frame . ,(window-frame))))
    >> (make-frame `((parent-frame . ,(window-frame))))
    >> (delete-frame)
    >> (delete-frame)
    >> (delete-frame)
    >> (delete-frame)
    >> (garbage-collect)

    Pip> That sounds like Robert's bug, but not like the one that's related to
    Pip> the "x = false" thing.

    Pip> Can you try the attached patch?

    Pip> diff --git a/src/nsterm.m b/src/nsterm.m
    Pip> index 03754e5ae5..c1d1d41117 100644
    Pip> --- a/src/nsterm.m
    Pip> +++ b/src/nsterm.m
    Pip> @@ -1644,6 +1644,7 @@ Hide the window (X11 semantics)
    Pip>    [view release];
 
    Pip>    xfree (f->output_data.ns);
    Pip> +  f->output_data.ns = NULL;
 
    Pip>    unblock_input ();
    Pip>  }

That has fixed things for me, not been able to crash it with Andrii's
recipe (I had to increase the number of frames to get it to crash).

Robert