On Mittwoch, 22. November 2017 11:32:22 CET Carsten Fuchs wrote: > That is, follow-up question: near the "..." above, we have got a target > "libjpeg", but how do I get the variables JPEG_INCLUDES, JPEG_LIBRARIES > etc. that `find_package(JPEG)` normally provides so that the last line > with the `target_link_libraries()` works? > I guess that defining them in `../ExtLibs/libjpeg/CMakeLists.txt` is wrong.
You've found an ugly corner in CMake ;-) The problem in this specific case is that CMake ships with a FindJPEG module that does not define modern import libs, but uses the old way of defining <PACKAGE>_LIBRARIES and <PACKAGE>_INCLUDE_DIRS. IMO this highlights one of the main problems with find modules: nobody really maintains them. If JPEG had proper imported targets, your code could look like this: find_package(JPEG) # without "REQUIRED" if (NOT JPEG_FOUND) ... # Proceed with the shipped copy of libjpeg: add_subdirectory(../ExtLibs/libjpeg ../ExtLibs/libjpeg) endif() target_link_libraries(main_program JPEG::JPEG) You just have to make sure that your shipped libjpeg creates the proper namespaced target: add_library(JPEG ...) add_library(JPEG::JPEG ALIAS JPEG) HTH, Johannes -- Powered by www.kitware.com Please keep messages on-topic and check the CMake FAQ at: http://www.cmake.org/Wiki/CMake_FAQ Kitware offers various services to support the CMake community. For more information on each offering, please visit: CMake Support: http://cmake.org/cmake/help/support.html CMake Consulting: http://cmake.org/cmake/help/consulting.html CMake Training Courses: http://cmake.org/cmake/help/training.html Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Follow this link to subscribe/unsubscribe: http://public.kitware.com/mailman/listinfo/cmake
