Differential D5838
remove CREATE_THREADS:=yes from api/multithreaded Makefile Authored by sbest on Oct 16 2014, 9:02 PM.
Details This flag triggers a '-lpthead' during the linking stage. Technically this is not needed since the multithreading is handled by std library, triggered by '-std=c++11' in build command line. The real reason I want to remove the '-lpthread' is it was causing a (linux/gcc built) test program to hang in a destructor for the std::condition_variable
Diff Detail
Event TimelineComment Actions On FreeBSD the test fails to link without -lpthread: os command: gmake clean LD_EXTRAS='-L/tank/emaste/src/llvm/build-nodebug/bin/../lib/python2.7/site-packages/../.. -llldb' EXE='test_listener_event_description' CFLAGS_EXTRAS='-std=c++11 -stdlib=libc++ -I/tank/emaste/src/llvm/tools/lldb/test/../include' CXX_SOURCES='driver.cpp listener_test.cpp test_listener_event_description.cpp'; gmake ARCH=amd64 CC="/usr/bin/clang" LD_EXTRAS='-L/tank/emaste/src/llvm/build-nodebug/bin/../lib/python2.7/site-packages/../.. -llldb' EXE='test_listener_event_description' CFLAGS_EXTRAS='-std=c++11 -stdlib=libc++ -I/tank/emaste/src/llvm/tools/lldb/test/../include' CXX_SOURCES='driver.cpp listener_test.cpp test_listener_event_description.cpp' with pid: 92054 stdout: rm -f "test_listener_event_description" driver.o listener_test.o test_listener_event_description.o driver.d listener_test.d test_listener_event_description.d rm -f -r rm -rf *.o *.d *.dSYM /usr/bin/clang++ -std=c++11 -g -O0 -m64 -std=c++11 -stdlib=libc++ -I/tank/emaste/src/llvm/tools/lldb/test/../include -I/tank/emaste/src/llvm/tools/lldb/test/make/../../include -c -o driver.o driver.cpp /usr/bin/clang++ -std=c++11 -g -O0 -m64 -std=c++11 -stdlib=libc++ -I/tank/emaste/src/llvm/tools/lldb/test/../include -I/tank/emaste/src/llvm/tools/lldb/test/make/../../include -c -o listener_test.o listener_test.cpp /usr/bin/clang++ -std=c++11 -g -O0 -m64 -std=c++11 -stdlib=libc++ -I/tank/emaste/src/llvm/tools/lldb/test/../include -I/tank/emaste/src/llvm/tools/lldb/test/make/../../include -c -o test_listener_event_description.o test_listener_event_description.cpp /usr/bin/clang++ driver.o listener_test.o test_listener_event_description.o -g -O0 -m64 -std=c++11 -stdlib=libc++ -I/tank/emaste/src/llvm/tools/lldb/test/../include -I/tank/emaste/src/llvm/tools/lldb/test/make/../../include -L/tank/emaste/src/llvm/build-nodebug/bin/../lib/python2.7/site-packages/../.. -llldb -o "test_listener_event_description" stderr: /usr/bin/ld: G: invalid DSO for symbol `pthread_create@@FBSD_1.0' definition //lib/libthr.so.3: could not read symbols: Bad value clang++: error: linker command failed with exit code 1 (use -v to see invocation) What do you think about an ENABLE_STD_THREADS := YES for these tests, and then a system-dependent library addition? My quick Google search suggests linking requirements for std::thread are quite system-dependent; AFAICT some Linuxes also need -lpthread -- perhaps a combination of the specific libc, libpthread, and libc++. Comment Actions
That seems like a reasonable way to go. And we just work out in the Comment Actions I have added another flag to test/Makefile.rules ENABLE_STD_THREADS and used it the api/Multithreaded unit tests. This can be used to selectively omit '-lpthreads' option for certain systems. All platforms except linux/gcc should behave as before. I have also made a Bugzilla report for simple program that hangs on linux ( http://llvm.org/bugs/show_bug.cgi?id=21553 ) I see there has been some recent activity in this area with r215562 omitting -lpthreads on windows, and r218899 recently adding -lpthreads as it was needed for FreeBSD. |