In FcStrListCreate() we were increasing reference count of set,
however, if set had a const reference (which is the case for list
of languages), and with multiple threads, the const ref (-1) was
getting up to 1 and then a decrease was destroying the set. Ouch.
Here's the valgrind error, which took me quite a few hours of
running to catch:
==4464== Invalid read of size 4
==4464== at 0x4E58FF3: FcStrListNext (fcstr.c:1256)
==4464== by 0x4E3F11D: FcConfigSubstituteWithPat (fccfg.c:1508)
==4464== by 0x4E3F8F4: FcConfigSubstitute (fccfg.c:1729)
==4464== by 0x4009FA: test_match (simple-pthread-test.c:53)
==4464== by 0x400A6E: run_test_in_thread (simple-pthread-test.c:68)
==4464== by 0x507EE99: start_thread (pthread_create.c:308)
==4464== Address 0x6bc0b44 is 4 bytes inside a block of size 24 free'd
==4464== at 0x4C2A82E: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4464== by 0x4E58F84: FcStrSetDestroy (fcstr.c:1236)
==4464== by 0x4E3F0C6: FcConfigSubstituteWithPat (fccfg.c:1507)
==4464== by 0x4E3F8F4: FcConfigSubstitute (fccfg.c:1729)
==4464== by 0x4009FA: test_match (simple-pthread-test.c:53)
==4464== by 0x400A6E: run_test_in_thread (simple-pthread-test.c:68)
==4464== by 0x507EE99: start_thread (pthread_create.c:308)
Thread test is running happily now. Will add the test in a moment.
Previously we were failing if CROSS_COMPILING and the generated headers
were not present. It works just fine now.
One caveat: the fix is not fully correct since config.h is being
included in the files built with CC_FOR_BUILD, but config.h has config
for the host system, not the build system. Should be fine though.
We used to have a shared-str pool. Removed to make thread-safety
work easier. My measurements show that the extra overhead is not
significant by any means.
These never worked as intended. The problem is, if Fontconfig tries to
read config files when these new types / constants are not registered,
it errs. As a result, no defined types / constants are usable from
config files. Which makes these really useless. Xft was the only user
of this API and even there it's not really used. Just kill it.
One inch closer to thread-safety since we can fix the object-type hash
table at compile time.
Behdad Esfahbod
Akira TAGOH