harfbuzz requires -lpthread, breaking the cairo_win32_surface_create_with_format check

[treeswift]

My initial attempt to build gtk3 on WSL hit the following ./configure error:

Failed to build package gtk3 for target armv7-w64-mingw32!
------------------------------------------------------------
checking for CAIRO... yes
checking for cairo_win32_surface_create_with_format in -lcairo... no
configure: error: cairo_win32_surface_create_with_format is not found in cairo library
You need a cairo snapshot 1.15.x or 1.16.x release or newer
make[1]: *** [Makefile:861: build-only-gtk3_armv7-w64-mingw32] Error 1
make[1]: Leaving directory '/home/username/Code/WoA32/mxe'

The configure log looks as follows:

configure:19427: checking for cairo_win32_surface_create_with_format in -lcairo
configure:19452: armv7-w64-mingw32-gcc -o conftest.exe -g -O2 -Wall -mms-bitfields -I/home/username/Code/WoA32/mxe/usr/armv7-w64-mingw32/include  conftest.c -lcairo   -lharfbuzz -lcairo -lgobject-2.0 -lffi -lfontconfig -lfreetype -lusp10 -lmsimg32 -lgdi32 -lpixman-1 -lexpat -lbz2 -lpng16 -lharfbuzz_too -lfreetype_too -lglib-2.0 -lintl -liconv -lpcre -lws2_32 -lole32 -lwinmm -lshlwapi -lm -lz    >&5
lld-link: error: undefined symbol: pthread_mutex_destroy
>>> referenced by libharfbuzz.a(libharfbuzz_la-hb-buffer.o):(hb_mutex_t::fini())
>>> referenced by libharfbuzz.a(libharfbuzz_la-hb-font.o)
>>> referenced by libharfbuzz.a(libharfbuzz_la-hb-set.o)

IOW, a missing Cairo symbol is mistakenly reported because a different (pthread) symbol is missing from the linker input.

For myself, I kinda quickfixed the build by providing -lpthread in freetype2.pc:Libs.private. However, since cairo.mk contains --disable-pthread, I assume the intention was to get rid of PThread in Cairo+dependencies. Therefore, I need a clarification what a desired permanent fix should be (either declare the pthread dependency or get rid of it in libhafbuzz).

My build environment is WSL v2, Ubuntu 20.04 on Windows 10. No Docker.

[pahaze]

Wow! I didn't realize that was the issue. Flew right over my head. I think personally that including pthreads instead of getting rid of it would be a better idea. That's just me, though.

[pahaze]

The intention never was to remove pthreads though. No clue why it's removed from the build.

[treeswift]

git-blame says:

commit 7b2f8beb9d2663e6e04e4d11b8b899e74943c4c8
Author: Volker Grabsch
Date: 3/5/09, 7:54 AM

disable threading in package cairo, because it conflicts with glib's threading

In my understanding though,

• -lharfbuzz is a separate beast;
• it only uses pthread mutex functions, and probably uses them locally/internally without exposing mutex objects via API;
• with static building, I don't think we have to worry about conflicting versions of pthread.

Then the fix would probably be as narrow as adding -lpthread to freetype2.pc as described above. Once I finally build a GTK GUI app and see that it works, I can refine a pull request.

[pahaze]

Sounds good

[pahaze]

Looking into this now, likely going to just use sed to add -lpthread to freetype2.pc cause it just seems like a better alternative than likely adding more issues to building than it's worth

[pahaze]

Fixed