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Re: [ft-devel] avoiding a longjmp crash in ftgrays.c


From: Werner LEMBERG
Subject: Re: [ft-devel] avoiding a longjmp crash in ftgrays.c
Date: Sun, 02 Jan 2011 08:31:51 +0100 (CET)

> A very short program (freetype_debug_gray.c) demonstrates the crash:
> [...]
>
> Unless there is a bug in that code,

At a first glance, the code looks fine.

> it seems the bug must be in MinGW
> GCC (4.5 and 3.4.4), or MS-Windows 7/Vista/XP, or FreeType
> 2.4.4.

I can try to replicate it on my GNU/Linux box, testing with valgrind
also.

> Possibly there is something the matter with MYFONT.TTF; still,
> ideally FreeType shouldn't crash no matter what is in the font.

Yep.

> If anyone is willing and able to investigate this, I'll try to come
> up with a smaller font containing just one glyph that causes the
> same crash. (Glyph 7211 is actually fairly simple, with only one
> contour; it's not the more intricate one with which the problem
> first occurred.)

Which font is it?  Maybe I already have it.  Otherwise, please send me
the font privately for further investigation.

> glyph count mismatch!  loca: 11664, maxp: 11663

This should be harmless.

> The output suddenly stops with "con", when the program
> crashes. Probably some output is lost (unflushed buffer?); I doubt
> the crash occurs in the middle of printing "conic".

The flushing out of stderr messages is not forced by FreeType but is
done by the OS.  Since FreeType doesn't emit any other messages this
isn't a problem normally.

> The difference between -fomit-frame-pointer and
> -fno-omit-frame-pointer seems to be important, but maybe not.  With
> GCC 4.5, it is currently making the difference between crashing or
> not.

Can you try a different compiler like MSVC?


    Werner



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