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coretext shaper causes segfault on "sparse" font #83

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justvanrossum opened this issue May 16, 2021 · 2 comments · Fixed by #84
Closed

coretext shaper causes segfault on "sparse" font #83

justvanrossum opened this issue May 16, 2021 · 2 comments · Fixed by #84

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@justvanrossum
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I have a font that only has GPOS, cmap, head, maxp and post tables, which works perfectly fine for the default (ot) shaper, but crashes hard when specifying the coretext shaper on macOS.

Relates to justvanrossum/fontgoggles#144

(FontGoggles compiles this kind of minimal fonts on the fly to do shaping for UFO sources: metrics come from the source via hb callbacks, and outlines are directly drawn from the sources, too.)

I'll open a PR that reproduces the problem.
@justvanrossum justvanrossum mentioned this issue May 16, 2021
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@behdad
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behdad commented May 16, 2021

(FontGoggles compiles this kind of minimal fonts on the fly to do shaping for UFO sources: metrics come from the source via hb callbacks, and outlines are directly drawn from the sources, too.)

Beautiful. I had designed HB to be used that way :).

Does the crash reproduce with hb-view?

@justvanrossum
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Beautiful. I had designed HB to be used that way :).

It's pretty fantastic indeed :)

Does the crash reproduce with hb-view?

It fails gracefully like this:

$ hb-view testfont.ttf ABC --shapers=coretext
hb-view: all shapers failed.
hb-view: FT_New_Memory_Face fail

So no, it doesn't crash.

@khaledhosny khaledhosny linked a pull request Jul 24, 2021 that will close this issue
Reproducing and fixing crash of #83 #84
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khaledhosny pushed a commit that referenced this issue Jul 24, 2021
@justvanrossum @khaledhosny
add test reproducing #83
a6096d7
khaledhosny added a commit that referenced this issue Jul 24, 2021
@khaledhosny
NULL-terminate shapers list
3f2560d 
hb_shape_full() takes a NULL-terminated array (the length of the array
is not passed separately) and would otherwise try to access random
memory and crash if all shapers failed.

Fixes #83
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Reproducing and fixing crash of #83
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@behdad @justvanrossum