opencv.pc file does not include static dependencies

[jeroen]

It looks like cmake does not populate the @OPENCV_PC_LIBS_PRIVATE@ field in opencv.pc, at least on MacOS. I am using the homebrew build of opencv. The opencv.pc file looks like this:

prefix=/usr/local/Cellar/opencv/3.4.2
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir_old=${prefix}/include/opencv
includedir_new=${prefix}/include

Name: OpenCV
Description: Open Source Computer Vision Library
Version: 3.4.2
Libs: -L${exec_prefix}/lib -lopencv_stitching -lopencv_superres -lopencv_videostab -lopencv_aruco -lopencv_bgsegm -lopencv_bioinspired -lopencv_ccalib -lopencv_dnn_objdetect -lopencv_dpm -lopencv_face -lopencv_photo -lopencv_fuzzy -lopencv_hfs -lopencv_img_hash -lopencv_line_descriptor -lopencv_optflow -lopencv_reg -lopencv_rgbd -lopencv_saliency -lopencv_stereo -lopencv_structured_light -lopencv_phase_unwrapping -lopencv_surface_matching -lopencv_tracking -lopencv_datasets -lopencv_dnn -lopencv_plot -lopencv_xfeatures2d -lopencv_shape -lopencv_video -lopencv_ml -lopencv_ximgproc -lopencv_calib3d -lopencv_features2d -lopencv_highgui -lopencv_videoio -lopencv_flann -lopencv_xobjdetect -lopencv_imgcodecs -lopencv_objdetect -lopencv_xphoto -lopencv_imgproc -lopencv_core
Libs.private:
Cflags: -I${includedir_old} -I${includedir_new}

As we can see the Libs.private: does not declare the static dependencies and therefore static linking fails. In the case of homebrew I would expect something like this in opencv.pc:

Libs.private: -ltbb -lippicv -lippiw -littnotify -llibjpeg-turbo -llibwebp -lpng -ltiff
Requires.private: openexr libavdevice

Obviously this depends on the exact configuration, but generally speaking, Requires.private names the .pc files for external libs that opencv was built (if they have a pc file), and Libs.private lists the bundled 3rdparty libs, and also external libs that do not have a pc file.

As a workaround I use the following to get the proper static linking LIBS:

LIBS_OPENCV=$(pkg-config --libs --static opencv)
LIBS_EXTRA=$(pkg-config --libs --static openexr libavdevice)
LIBS_STATIC="-ltbb -lippicv -lippiw -littnotify -llibjpeg-turbo -llibwebp -lpng -ltiff"
LIBS="$LIBS_OPENCV $LIBS_STATIC $LIBS_EXTRA"