[Fontconfig] Fontconfig 2.12.1 unable to cache /System/Library/Fonts on OS X

[Zhiming Wang]

I sent the same report to the mailing list a few days ago, but it never
appeared on the archive (maybe because I didn't subscribe at that time), so I'm
not sure if it reached anyone and am resending the message. In the meantime, a
report titled "fontconfig performance issue on macOS" has been posted to the
list, which should be the same issue, but it didn't provide any details, so
I'm starting a new thread.

-------------------------------------------------------------------------------

Fontconfig 2.12.0 works fine on OS X (10.11.6), but 2.12.1 is unable to cache
/System/Library/Fonts. Whenever I try to cache it, I always get an error:

   /path/to/cache: invalid cache file: b0a71e6bf6a8a1a908413a823d76e21f-le64.cache-7

and no cache is created. This renders fontconfig 2.12.1 unusable -- every
single operation needs to go through a lengthy (failed) recache of
/System/Library/Fonts.

git-bisect tracks the issue down to 7a4a5bd "Properly validate offsets in cache
files."

Unfortunately I do not know what additional info may be helpful for debugging
purposes. For your reference, here's a valid cache of /System/Library/Fonts
created by fontconfig 2.12.0:

   https://dl.bintray.com/zmwangx/generic/fontconfig-2.12.0-cache.tar.gz
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 801 bytes
Desc: Message signed with OpenPGP using GPGMail
URL: <https://lists.freedesktop.org/archives/fontconfig/attachments/20160828/c9b5c581/attachment.sig>