lock: fix link error with --enable-threads=pth

[Bruno Haible]

When building a testdir with --enable-threads=pth --with-libpth-prefix=...
I see link errors:

gcc  -g -O2   -o test-fstrcmp test-fstrcmp.o libtests.a ../gllib/libgnu.a 
libtests.a    -lm -lm -lm -lm -lm -lm -lm -lm -lm -lm -lm
../gllib/libgnu.a(lock.o): In function `glthread_rwlock_init_multithreaded':
/media/develdata/devel/GNULIB/testdir-all/build-pth/gllib/../../gllib/glthread/lock.c:518:
 undefined reference to `pth_cond_init'
/media/develdata/devel/GNULIB/testdir-all/build-pth/gllib/../../gllib/glthread/lock.c:520:
 undefined reference to `pth_cond_init'
../gllib/libgnu.a(lock.o): In function `glthread_rwlock_rdlock_multithreaded':
/media/develdata/devel/GNULIB/testdir-all/build-pth/gllib/../../gllib/glthread/lock.c:543:
 undefined reference to `pth_cond_await'
../gllib/libgnu.a(lock.o): In function `glthread_rwlock_wrlock_multithreaded':
/media/develdata/devel/GNULIB/testdir-all/build-pth/gllib/../../gllib/glthread/lock.c:567:
 undefined reference to `pth_cond_await'
../gllib/libgnu.a(lock.o): In function `glthread_rwlock_unlock_multithreaded':
/media/develdata/devel/GNULIB/testdir-all/build-pth/gllib/../../gllib/glthread/lock.c:616:
 undefined reference to `pth_cond_notify'
/media/develdata/devel/GNULIB/testdir-all/build-pth/gllib/../../gllib/glthread/lock.c:626:
 undefined reference to `pth_cond_notify'
collect2: error: ld returned 1 exit status
Makefile:14436: recipe for target 'test-fstrcmp' failed
make[3]: *** [test-fstrcmp] Error 1

gcc  -g -O2   -o test-once1 test-once.o libtests.a ../gllib/libgnu.a libtests.a 
  -lm -lm -lm -lm -lm -lm -lm -lm -lm -lm -lm
../gllib/libgnu.a(lock.o): In function `glthread_rwlock_init_multithreaded':
/media/develdata/devel/GNULIB/testdir-all/build-pth/gllib/../../gllib/glthread/lock.c:518:
 undefined reference to `pth_cond_init'
/media/develdata/devel/GNULIB/testdir-all/build-pth/gllib/../../gllib/glthread/lock.c:520:
 undefined reference to `pth_cond_init'
../gllib/libgnu.a(lock.o): In function `glthread_rwlock_rdlock_multithreaded':
/media/develdata/devel/GNULIB/testdir-all/build-pth/gllib/../../gllib/glthread/lock.c:543:
 undefined reference to `pth_cond_await'
../gllib/libgnu.a(lock.o): In function `glthread_rwlock_wrlock_multithreaded':
/media/develdata/devel/GNULIB/testdir-all/build-pth/gllib/../../gllib/glthread/lock.c:567:
 undefined reference to `pth_cond_await'
../gllib/libgnu.a(lock.o): In function `glthread_rwlock_unlock_multithreaded':
/media/develdata/devel/GNULIB/testdir-all/build-pth/gllib/../../gllib/glthread/lock.c:616:
 undefined reference to `pth_cond_notify'
/media/develdata/devel/GNULIB/testdir-all/build-pth/gllib/../../gllib/glthread/lock.c:626:
 undefined reference to `pth_cond_notify'
collect2: error: ld returned 1 exit status
Makefile:15438: recipe for target 'test-once1' failed
make[3]: *** [test-once1] Error 1

This patch fixes them. Will push soon.


2019-01-04  Bruno Haible  <address@hidden>

        lock: Fix link error with --enable-threads=pth.
        * lib/glthread/lock.h (pth_cond_init, pth_cond_await, pth_cond_notify):
        Mark as weak.

diff --git a/lib/glthread/lock.h b/lib/glthread/lock.h
index c0fa53e..6e1fdf8 100644
--- a/lib/glthread/lock.h
+++ b/lib/glthread/lock.h
@@ -416,6 +416,9 @@ extern "C" {
 #  pragma weak pth_rwlock_acquire
 #  pragma weak pth_rwlock_release
 #  pragma weak pth_once
+#  pragma weak pth_cond_init
+#  pragma weak pth_cond_await
+#  pragma weak pth_cond_notify
 
 #  pragma weak pth_cancel
 #  define pth_in_use() (pth_cancel != NULL)