[Octave-bug-tracker] [bug #41699] imformats causes a segmentation fault on Windows when Octave exits

[Mike Miller]

Follow-up Comment #85, bug #41699 (project octave):

Ok, here is a minimum working example that exhibits the segmentation fault
when Octave exits.


function formats = whatever ()
  persistent formats = struct ( "coder", {},
                                "ext", {},
                                "isa", {},
                                "info", {},
                                "read", {},
                                "write", {},
                                "alpha", {},
                                "description", {},
                                "multipage", {});
  formats(1).coder = "CUR";
  formats = __magick_formats__ (formats);
endfunction


I was originally testing with "PNG" as the only format, but it did not
segfault. Using "CUR" or "ICO" as the only format does segfault. So going back
to the original imformats.m, commenting out both "CUR" and "ICO" no longer
segfaults.

Is there something about these two formats in GraphicsMagick on Windows that
would cause this segmentation fault or is it just random coincidence that it
happens for me only with these two? Can someone else verify that commenting
out these two formats in imformats.m fixes the segfault on exit?

So the combination of things that are required to cause the segfault for me
are

* persistent struct array in a function
* copying the return value from the oct-file function __magick_formats__ into
the persistent struct array
* using the "CUR" or "ICO" image formats

If the struct array is not persistent, no segfault. If neither of those
formats is passed into GM, no segfault. If the return value of
__magick_formats__ is not assigned back into the struct array, no segfault.

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