[Devel] Recursive composite glyphs

[Owen Taylor]

A problem was reported to me where freetype, when given a
corrupt font that looks like it has a recursive composite
glyph, overflows it's stack and crashes. (After allocating
a huge amount of memory.)

The attached patch makes two changes in this area:

 - When loading composite glyphs, it puts a hard recursion
   limit of 5 on the loading, which should be enough for
   any real situation. (The TrueType spec doesn't make 
   clear whether composite glyphs can have composite
   glyphs as subglyphs at all.)

 - It makes the check for what is a composite glyph 
   stricter; only glyphs with a contours_count of -1,
   not any negative number, are considered composite glyphs.

   (-1 is what the TT spec requires, and this will reduce
   the chance of random garbage looking like a composite
   glyph.)

Regards,
                                        Owen

freetype-composite-recurse.patch
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