bug#31316: Emacs hangs in `font_open_entity'

[Werner LEMBERG]

If I call `emacs -Q' and load the attached file `testchar' with

  C-x RET c gb18030 C-x C-f testchar

Emacs hangs in `font_open_entity' on my GNU/Linux box:

  for (psize = pixel_size; ; psize++)
    {
      font_object = driver_list->driver->open (f, entity, psize);
      if (NILP (font_object))
        return Qnil;
      font = XFONT_OBJECT (font_object);
      if (font->average_width > 0 && font->height > 0)
        break;
    }

Both `average_width' and `height' are always zero for `font'
regardless of `psize'; this effectively makes the above code an
endless loop.



In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.20.10)
 of 2018-04-30 built on linux
Repository revision: bca6c4348077c8c0b368503b16378867b6d49659
Windowing system distributor 'The X.Org Foundation', version 11.0.11803000
System Description: openSUSE Leap 42.3

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Configured using:
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Memory information:
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