[CMake] Building project with Boost thread, TBB, OpenCV, QT, -lpthread missing

[Johannes Jordan]

Hello,


I am running a project that uses several libs which seemingly rely on
pthread. In my CMake files, I don't explicitely refer to pthread
(especially as it is a different story under different OS's like
Windows). Instead I use the find_package logic, e.g.:

find_package(Boost ${VOLE_MINIMUM_BOOST_VERSION} COMPONENTS thread)

then use "${Boost_INCLUDE_DIR}/include/;${Boost_INCLUDE_DIR}",
${Boost_THREAD_LIBRARY} appropriately.

On the GNU/Linux systems I tested, I get a linker output like this:

/usr/bin/g++    -Wall -Wno-long-long -Wno-reorder -pedantic  -O3
-DNDEBUG    CMakeFiles/qgerbil.dir/main.cpp.o
CMakeFiles/qgerbil.dir/qrc_gerbil.cxx.o  -o ../../bin/qgerbil -rdynamic
../core/libcore-lib.a libgerbil_gui-lib.a -lQtOpenGL -lGLU -lGL -lSM
-lICE -lX11 -lXext ../rgb/librgb-lib.a ../../librgb-optional-lib.a
../seg_graphs/libseg_graphs-lib.a ../csparse/libcsparse-lib.a
../../libseg_graphs-optional-lib.a ../../libgerbil_gui-optional-lib.a
../seg_meanshift/libseg_meanshift-lib.a ../lsh/liblsh-lib.a
../../libseg_meanshift-optional-lib.a
../seg_felzenszwalb/libseg_felzenszwalb-lib.a
../edge_detect/libedge_detect-lib.a ../som/libsom-lib.a
../imginput/libimginput-lib.a -lgdal
../similarity_measures/libsimilarity_measures-lib.a
../core/libcore-lib.a -ltbb -lboost_system -lboost_filesystem -lQtCore
-lQtGui -lboost_thread -lboost_date_time -lboost_chrono
/usr/lib/libopencv_videostab.so.2.4.9 /usr/lib/libopencv_ts.a -ldl -lm
-lpthread -lrt -lGLU -lGL -lSM -lICE -lX11 -lXext -ltbb
/usr/lib/libopencv_superres.so.2.4.9
/usr/lib/libopencv_stitching.so.2.4.9
/usr/lib/libopencv_contrib.so.2.4.9 /usr/lib/libopencv_nonfree.so.2.4.9
/usr/lib/libopencv_ocl.so.2.4.9 /usr/lib/libopencv_gpu.so.2.4.9
/usr/lib/libopencv_photo.so.2.4.9 /usr/lib/libopencv_objdetect.so.2.4.9
/usr/lib/libopencv_legacy.so.2.4.9 /usr/lib/libopencv_video.so.2.4.9
/usr/lib/libopencv_ml.so.2.4.9 /usr/lib/libopencv_calib3d.so.2.4.9
/usr/lib/libopencv_features2d.so.2.4.9
/usr/lib/libopencv_highgui.so.2.4.9 /usr/lib/libopencv_imgproc.so.2.4.9
/usr/lib/libopencv_flann.so.2.4.9 /usr/lib/libopencv_core.so.2.4.9
-lboost_program_options

Now a user wrote me that he gets this output:

/usr/bin/c++    -Wall -Wno-long-long -Wno-reorder -pedantic  -O3
-DNDEBUG    CMakeFiles/qgerbil.dir/main.cpp.o
CMakeFiles/qgerbil.dir/qrc_gerbil.cxx.o  -o ../../bin/qgerbil -rdynamic
../core/libcore-lib.a libgerbil_gui-lib.a /usr/lib64/qt4/libQtOpenGL.so
-lGLU -lGL -lSM -lICE -lX11 -lXext ../rgb/librgb-lib.a
../../librgb-optional-lib.a ../seg_graphs/libseg_graphs-lib.a
../csparse/libcsparse-lib.a ../../libseg_graphs-optional-lib.a
../../libgerbil_gui-optional-lib.a
../seg_meanshift/libseg_meanshift-lib.a ../lsh/liblsh-lib.a
../../libseg_meanshift-optional-lib.a
../seg_felzenszwalb/libseg_felzenszwalb-lib.a
../edge_detect/libedge_detect-lib.a ../som/libsom-lib.a
../imginput/libimginput-lib.a -lgdal
../similarity_measures/libsimilarity_measures-lib.a
../core/libcore-lib.a -ltbb -lboost_system-mt -lboost_filesystem-mt
/usr/lib64/qt4/libQtCore.so /usr/lib64/qt4/libQtGui.so -lboost_thread-mt
-lboost_date_time-mt -lboost_chrono-mt -lopencv_calib3d -lopencv_contrib
-lopencv_core -lopencv_features2d -lopencv_flann -lopencv_gpu
-lopencv_highgui -lopencv_imgproc -lopencv_legacy -lopencv_ml
-lopencv_nonfree -lopencv_objdetect -lopencv_photo -lopencv_stitching
-lopencv_superres -lopencv_ts -lopencv_video -lopencv_videostab
-lboost_program_options-mt -Wl,-rpath,/usr/lib64/qt4


I see two differences:
1. -ldl -lm -lpthread -lrt are missing
2. both Qt and OpenCV libs are referenced differently (in an opposing way)


Can anybody shed light on the issue how my user might have obtained this
different behaviour? What can or should I do in my CMake files to
prevent this problem from happening. The successful workaround my user
applied is to set CFLAGS='-lpthread'. Obviously that is not a good
solution, but it shows that there are no other issues in the build (and
it seems that missing -ldl -lm -lrt doesn't matter).


Thank you for your time and your help!


Best Regards,
Johannes

p.s.: the project can be found at http://gerbilvis.org