Context:
I have a cpp program built on MacOS 12.6 with the following CMakeLists.txt file.
cmake_minimum_required(VERSION 3.19.0)
project(cpp-test VERSION 0.1.0)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED True)
add_executable(cpp-test main.cpp)
add_library(test-helpers main.cpp ${PROJECT_SOURCE_DIR}/helpers.hpp)
set(CPACK_PROJECT_NAME ${PROJECT_NAME})
set(CPACK_PROJECT_VERSION ${PROJECT_VERSION})
include(CPack)
# this is super important in order for cmake to include the vcpkg search/lib paths!
set(CMAKE_TOOLCHAIN_FILE "$ENV{VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake" CACHE STRING "")
# find library and its headers
find_path(IXWEBSOCKET_INCLUDE_DIR ixwebsocket/IXWebSocket.h)
find_library(IXWEBSOCKET_LIBRARY ixwebsocket)
find_package(OpenSSL REQUIRED)
find_package(CURL REQUIRED)
# include headers
include_directories(${IXWEBSOCKET_INCLUDE_DIR} ${CURL_INCLUDE_DIR})
# Cmake will automatically fail the generation if the lib was not found, i.e is set to NOTFOUND
target_link_libraries(
${PROJECT_NAME} PRIVATE
${IXWEBSOCKET_LIBRARY}
OpenSSL::SSL
OpenSSL::Crypto
${CURL_LIBRARIES}
"-framework Foundation"
"-framework Security"
"-lz"
)
This compiles just fine. However, when I try to pull it into my Ubuntu VM and try to build it /build> cmake .., I get the following errors
CMake Error in CMakeLists.txt:
Found relative path while evaluating include directories of "cpp-test":
"IXWEBSOCKET_INCLUDE_DIR-NOTFOUND"
CMake Error in CMakeLists.txt:
Found relative path while evaluating include directories of
"test-helpers":
"IXWEBSOCKET_INCLUDE_DIR-NOTFOUND"
-- Generating done
What I have tried...
I have installed vcpkg and created my symlink ln -s /path/to/vcpkg /usr/local/bin/vcpkg.
I have installed ixwebsocket via vcpkg install ixwebsocket, but it seems that the CMAKE_TOOLCHAIN_FILE is not being parsed correctly.
I'm a bit lost, any help would be appreciated
This is not a great answer to the issue, but I ended up resolving it by building ixwebsocket via CMake instead.
It seems that vcpkg was not compatible with the linux distro in my VM.
Currently I'm trying to make some spectogram generation for my uni project. I'm trying to build a static library where all the magic will work and just call it from the main() function.
This is my cmake file:
set(CMAKE_CXX_STANDARD 17)
project(demo)
find_package(SndFile REQUIRED)
add_subdirectory(spectogram)
add_executable(demo main.cpp)
target_link_libraries (demo LINK_PUBLIC Spectrogram)
target_link_libraries(demo PRIVATE SndFile::sndfile)
I have installed libsndfile via homebrew, but find_package() refuses to locate the lib and throws this error:
CMake Error at CMakeLists.txt:6 (find_package):
By not providing "FindSndFile.cmake" in CMAKE_MODULE_PATH this project has
asked CMake to find a package configuration file provided by "SndFile", but
CMake did not find one.
Could not find a package configuration file provided by "SndFile" with any
of the following names:
SndFileConfig.cmake
sndfile-config.cmake
Add the installation prefix of "SndFile" to CMAKE_PREFIX_PATH or set
"SndFile_DIR" to a directory containing one of the above files. If
"SndFile" provides a separate development package or SDK, be sure it has
been installed.
-- Configuring incomplete, errors occurred!
I`ve made some research and found out that libsndfile does not have any .cmake configs inside like other libs, that I can link easily (like OpenCV or spdlog). I would really appreciate any help to solve this horror.
With help of Tsyvarev, I figured out the solution. I used the pkg-config module and a custom cmake file, I found on the web. I will include my final cmake in case someone else will need it:
cmake_minimum_required(VERSION 3.17)
set(CMAKE_CXX_STANDARD 17)
project(demo)
# - Try to find libsndfile
# Once done, this will define
#
# LIBSNDFILE_FOUND - system has libsndfile
# LIBSNDFILE_INCLUDE_DIRS - the libsndfile include directories
# LIBSNDFILE_LIBRARIES - link these to use libsndfile
# Use pkg-config to get hints about paths
find_package(PkgConfig QUIET)
if(PKG_CONFIG_FOUND)
pkg_check_modules(LIBSNDFILE_PKGCONF sndfile)
endif(PKG_CONFIG_FOUND)
# Include dir
find_path(LIBSNDFILE_INCLUDE_DIR
NAMES sndfile.h
PATHS ${LIBSNDFILE_PKGCONF_INCLUDE_DIRS}
)
# Library
find_library(LIBSNDFILE_LIBRARY
NAMES sndfile libsndfile-1
PATHS ${LIBSNDFILE_PKGCONF_LIBRARY_DIRS}
)
find_package(PackageHandleStandardArgs)
find_package_handle_standard_args(LibSndFile DEFAULT_MSG LIBSNDFILE_LIBRARY LIBSNDFILE_INCLUDE_DIR)
if(LIBSNDFILE_FOUND)
set(LIBSNDFILE_LIBRARIES ${LIBSNDFILE_LIBRARY})
set(LIBSNDFILE_INCLUDE_DIRS ${LIBSNDFILE_INCLUDE_DIR})
endif(LIBSNDFILE_FOUND)
mark_as_advanced(LIBSNDFILE_LIBRARY LIBSNDFILE_LIBRARIES LIBSNDFILE_INCLUDE_DIR LIBSNDFILE_INCLUDE_DIRS)
include(FindPkgConfig)
pkg_search_module(SndFile REQUIRED sndfile)
include_directories(${LIBSNDFILE_INCLUDE_DIRS})
add_subdirectory(spectogram)
add_executable(demo main.cpp)
message(STATUS "sndfile include dirs path: ${LIBSNDFILE_INCLUDE_DIRS}")
message(STATUS "sndfile libs path: ${LIBSNDFILE_LIBRARIES}")
target_link_libraries (demo LINK_PUBLIC Spectrogram)
target_link_libraries(demo PRIVATE ${LIBSNDFILE_LIBRARIES})
I'm trying to use Caffe in my C++ project which I compile with CMakeLists.txt, but it doesn't want to work. My only line in the code is
#include <caffe/caffe.hpp>
I compiled Caffe myself, it is installed in the directory "/home/tamas/caffe". My CMakeLists.txt looks like this so far:
cmake_minimum_required (VERSION 3.5)
include(FindPkgConfig)
project (main)
set (CMAKE_CXX_STANDARD 11)
set (CMAKE_CXX_STANDARD_REQUIRED TRUE)
set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Werror -std=c++11 -pthread")
set (source_dir "${PROJECT_SOURCE_DIR}/src/")
set (OpenCV_DIR "/home/tamas/opencv/include/opencv2")
set (Caffe_DIR "/home/tamas/caffe")
file (GLOB source_files "${source_dir}/ssd_video.cpp")
find_package(OpenCV 4.4.0 REQUIRED)
include_directories(${OpenCV_INCLUDE_DIRS})
find_package(Caffe REQUIRED)
include_directories(${Caffe_INCLUDE_DIRS})
add_executable (main ${source_files})
target_link_libraries(main ${OpenCV_LIBS})
target_link_libraries(main ${Caffe_LIBRARIES})
The error is the following:
CMake Error at CMakeLists.txt:24 (find_package):
By not providing "FindCaffe.cmake" in CMAKE_MODULE_PATH this project has
asked CMake to find a package configuration file provided by "Caffe", but
CMake did not find one.
Could not find a package configuration file provided by "Caffe" with any of
the following names:
CaffeConfig.cmake
caffe-config.cmake
Add the installation prefix of "Caffe" to CMAKE_PREFIX_PATH or set
"Caffe_DIR" to a directory containing one of the above files. If "Caffe"
provides a separate development package or SDK, be sure it has been
installed.
-- Configuring incomplete, errors occurred!
The problem is that I have searched and I don't have a FindCaffe.cmake file on my computer. I found an example for CaffeConfig.cmake, but I tried it and it doesn't work either.
Is there a way I can link Caffe with my C++ project? Thanks!
To fix this issue you may do the following:
Download this FindCAFFE.cmake file
Create cmake dir in your repo root directory and put the downloaded file there.
Modify your CMake file:
add set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${PROJECT_SOURCE_DIR}/cmake")
change set (Caffe_DIR "/home/tamas/caffe") to set (CAFFE_ROOT_DIR "/home/tamas/caffe")
change find_package(Caffe REQUIRED) to find_package(CAFFE REQUIRED)
use CAFFE_INCLUDE_DIRS and CAFFE_LIBRARIES for include directories and link libraries respectively
Clean up your build dir and run cmake command again
<library>_DIR should not be set manually in CMake code usually. There are better alternatives that should be used as setting these variable won't necessarily do what you want. It won't change where find_package finds its libraries.
The CaffeConfig.cmake file is generated when building Caffe. You should never download another one, these files are compatible only with a specific build configuration.
The Caffe library supports to be used with CMake, so FindCaffe.cmake is unnecessary.
For find_package to work, either set the <package>_ROOT variable (require CMake 3.12 minimum) or you must append the install path in CMAKE_PREFIX_PATH. Here's a CMake example that uses the prefix path:
# If you only built the library
list (APPEND CMAKE_PREFIX_PATH "/home/tamas/caffe/build-dir")
# If you installed the library there
list (APPEND CMAKE_PREFIX_PATH "/home/tamas/caffe/")
find_package(Caffe REQUIRED)
Note that the Caffe_LIBRARIES and Caffe_INCLUDE_DIRS won't be set. This is old CMake style and the Caffe library uses the new style. This is what you should do:
target_link_libraries(main PUBLIC caffe caffeproto)
This line add both include directory and adds linking to the libraries too.
I'm trying to use CLion to create a SDL2 project.
The problem is that the SDL headers can't be found when using #include's.
My CMakeLists.txt file:
cmake_minimum_required(VERSION 2.8.4)
project(ChickenShooter)
set(SDL2_INCLUDE_DIR C:/SDL/SDL2-2.0.3/include)
set(SDL2_LIBRARY C:/SDL/SDL2-2.0.3/lib/x64)
include_directories(${SDL2_INCLUDE_DIR})
set(SOURCE_FILES main.cpp)
add_executable(ChickenShooter ${SOURCE_FILES})
target_link_libraries(ChickenShooter ${SDL2_LIBRARY})
My test main.cpp:
#include <iostream>
#include "SDL.h" /* This one can't be found */
int main(){
if (SDL_Init(SDL_INIT_VIDEO) != 0){
std::cout << "SDL_Init Error: " << SDL_GetError() << std::endl;
return 1;
}
SDL_Quit();
return 0;
}
Thank you for any help you could give me.
Edit:
I'm using Windows and CLion is configured to use cygwin64.
This blog post shows how you can do it: Using SDL2 with CMake
On Linux you can use a recent CMake (e.g. version 3.7) and using SDL2 works out of the box.
cmake_minimum_required(VERSION 3.7)
project(SDL2Test)
find_package(SDL2 REQUIRED)
include_directories(SDL2Test ${SDL2_INCLUDE_DIRS})
add_executable(SDL2Test Main.cpp)
target_link_libraries(SDL2Test ${SDL2_LIBRARIES})
Under Windows you can download the SDL2 development package, extract it somewhere and then create a sdl-config.cmake file in the extracted location with the following content:
set(SDL2_INCLUDE_DIRS "${CMAKE_CURRENT_LIST_DIR}/include")
# Support both 32 and 64 bit builds
if (${CMAKE_SIZEOF_VOID_P} MATCHES 8)
set(SDL2_LIBRARIES "${CMAKE_CURRENT_LIST_DIR}/lib/x64/SDL2.lib;${CMAKE_CURRENT_LIST_DIR}/lib/x64/SDL2main.lib")
else ()
set(SDL2_LIBRARIES "${CMAKE_CURRENT_LIST_DIR}/lib/x86/SDL2.lib;${CMAKE_CURRENT_LIST_DIR}/lib/x86/SDL2main.lib")
endif ()
string(STRIP "${SDL2_LIBRARIES}" SDL2_LIBRARIES)
When you now configure inside the CMake-GUI application there will be a SDL2_DIR variable. You have to point it to the SDL2 directory where you extracted the dev package and reconfigure then everything should work.
You can then include SDL2 headers by just writing #include "SDL.h".
Don't set the path to SDL2 by hand. Use the proper find command which uses FindSDL. Should look like:
find_file(SDL2_INCLUDE_DIR NAME SDL.h HINTS SDL2)
find_library(SDL2_LIBRARY NAME SDL2)
add_executable(ChickenShooter main.cpp)
target_include_directories(ChickenShooter ${SDL2_INCLUDE_DIR})
target_link_libraries(ChickenShooter ${SDL2_LIBRARY})
If SDL2 is not found, you have to add the path to SDL2 to CMAKE_PREFIX_PATH, that's the place where CMake looks for installed software.
If you can use Pkg-config, its use might be easier, see How to use SDL2 and SDL_image with cmake
If you feel more comfortable to use a FindSDL2.cmake file similar to FindSDL.cmake provided by CMake, see https://brendanwhitfield.wordpress.com/2015/02/26/using-cmake-with-sdl2/
You can also pull in the SDL source repository as a submodule and build/link it statically along with your main program via add_subdirectory() and target_link_libraries():
cmake_minimum_required( VERSION 3.18.0 )
project( sdl2-demo )
set( SDL_STATIC ON CACHE BOOL "" FORCE )
set( SDL_SHARED OFF CACHE BOOL "" FORCE )
# 'external/sdl' should point at a SDL
# repo clone or extracted release tarball
add_subdirectory( external/sdl )
add_executable(
${CMAKE_PROJECT_NAME}
"src/main.cpp"
)
target_link_libraries( ${CMAKE_PROJECT_NAME} SDL2main SDL2-static )
(At least as of the release-2.0.9 tag, possibly earlier.)
I recently discovered the latest version of SDL2 (version 2.0.12) now comes with all the required CMake config/install scripts, so there's no need to use FindSDL anymore.
I downloaded the SDL source from https://www.libsdl.org/download-2.0.php then from the root folder ran...
cmake -S . -B build/debug -G Ninja -DCMAKE_INSTALL_PREFIX=./install -DCMAKE_BUILD_TYPE=Debug
cmake --build build/debug --target install
This will build and install the debug version of the library, you can then also run...
cmake -S . -B build/release -G Ninja -DCMAKE_INSTALL_PREFIX=./install -DCMAKE_BUILD_TYPE=Release
cmake --build build/release --target install
Which will build and install the release version of the library (and because the SDL CMake script uses DEBUG_POSTFIX the release version of the library won't overwrite the debug one as the debug versions all have 'd' appended to their name).
In your CMakeLists.txt file you can then simply do this:
find_package(SDL2 REQUIRED)
add_executable(${PROJECT_NAME} ...)
target_link_libraries(
${PROJECT_NAME} PRIVATE
SDL2::SDL2
SDL2::SDL2main
You'll need to tell your application where to find the SDL install folder if you used a custom location as I've done in the example. To do this from the root folder of your app run:
cmake -S . -B build/debug -G Ninja -DCMAKE_BUILD_TYPE=Debug -DCMAKE_PREFIX_PATH=</absolute/path/to/install/dir>
cmake --build build/debug
Note: You can use $(pwd) (*nix/macOS) or %cd% (Windows) to create a hybrid relative path which can be very useful.
You can omit both DCMAKE_INSTALL_PREFIX and DCMAKE_PREFIX_PATH if you want to install SDL to the default system location.
In the examples I've opted to use the Ninja generator as it is consistent across macOS/Windows - it can be used with MSVC/Visual Studio, just make sure you run this (path may differ slightly depending on year/version) to add Ninja to your path.
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars64.bat
Update:
One other thing I remembered which is useful on Windows is the ability to copy the SDL .dll file into the application binary directory, this can be achieved like so:
if (WIN32)
# copy the .dll file to the same folder as the executable
add_custom_command(
TARGET ${PROJECT_NAME} POST_BUILD
COMMAND ${CMAKE_COMMAND} -E copy_if_different
$<TARGET_FILE:SDL2::SDL2>
$<TARGET_FILE_DIR:${PROJECT_NAME}>
VERBATIM)
endif()
Using the SDL2 CMake module that I developed, you can integrate the SDL2 library easily in a modern and portable approach.
You should just copy the module in cmake/sdl2 (Or just clone the modules repo) in your project:
git clone https://github.com/aminosbh/sdl2-cmake-modules cmake/sdl2
Then add the following lines in your CMakeLists.txt:
list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake/sdl2)
find_package(SDL2 REQUIRED)
target_link_libraries(${PROJECT_NAME} SDL2::Main)
Note: If CMake didn't find the SDL2 library (in Windows), we can specify the CMake option SDL2_PATH as follows:
cmake .. -DSDL2_PATH="/path/to/sdl2"
For more details, please read the README.md file.
The SDL2 CMake modules support other related libraries : SDL2_image, SDL2_ttf, SDL2_mixer, SDL2_net and SDL2_gfx.
You can find a list of examples/samples and projects that uses these modules here : https://github.com/aminosbh/sdl-samples-and-projects
With the compiled version of SDL2-2.0.9 with MinGW-w64 in Windows, the following configuration works for me:
find_package(SDL2 REQUIRED)
add_executable(sdl-test ${SOURCES})
target_link_libraries(sdl-test
mingw32
SDL2::SDL2main
SDL2::SDL2
)
A longer explanation
By reading SDL2Targets.cmake file, I've learned that SDL2 is providing several targets:
SDL2::SDL2main (lib/libSDL2main.a)
SDL2::SDL2 (lib/libSDL2.dll.a)
SDL2::SDL2-static (lib/libSDL2-static.a)
Each of them has INTERFACE_INCLUDE_DIRECTORIES defined, which means we don't need to manually specify include_directories for SDL2.
But by only adding SDL2::SDL2main and SDL2::SDL2 as target_link_libraries is not enough. The g++ compiler might be complaining about "undefined reference to `WinMain'".
By inspecting the compiler options, I found that the SDL2 libraries are added before -lmingw32 option. In order to make the -lmingw32 option comes before SDL2 libraries, we have to also specify mingw32 as the first target_link_libraries. Which will make this configuration working.
The command that I have used for building it is:
$ mkdir build && cd build && cmake .. -G"MinGW Makefiles" && cmake --build .
The only small problem here is in the finally generated compiler options, the -lmingw32 option is duplicated. But since it doesn't affect the linking process, I've ignored it for now.
On Linux, in Clion, this works:
cmake_minimum_required(VERSION 3.20)
project(first_game)
set(CMAKE_CXX_STANDARD 14)
find_package(SDL2 REQUIRED)
include_directories(${SDL2_INCLUDE_DIRS})
add_executable(${PROJECT_NAME} main.cpp)
target_link_libraries(${PROJECT_NAME} ${SDL2_LIBRARIES})
You don't seems to have a CMake error whike generating your make file. But I think your problem is, the SDL Header are located in a subfolder named "SDL2".
Change your CMakeLists.txt to include
C:/SDL/SDL2-2.0.3/include/SDL2
Instead of
C:/SDL/SDL2-2.0.3/include
I had the same problem and none of the other solutions worked.
But I finally got it working by following this solution : How to properly link libraries with cmake?
In a nutshell, the problem was that the SDL2 library was not linked properly in my CMakeLists.txt. And by writing this into the file, it worked (more explainations in the other thread) :
project (MyProgramExecBlaBla) #not sure whether this should be the same name of the executable, but I always see that "convention"
cmake_minimum_required(VERSION 2.8)
ADD_LIBRARY(LibsModule
file1.cpp
file2.cpp
)
target_link_libraries(LibsModule -lpthread)
target_link_libraries(LibsModule liblapack.a)
target_link_libraries(LibsModule -L/home/user/libs/somelibpath/)
ADD_EXECUTABLE(MyProgramExecBlaBla main.cpp)
target_link_libraries(MyProgramExecBlaBla LibsModule)
Highlighting the steps of how I was able to eventually accomplish this using the FindSDL2.cmake module:
Download SDL2-devel-2.0.9-VC.zip (or whatever version is out after this answer is posted) under the Development Libraries section of the downloads page.
Extract the zip folder and you should see a folder similar to "SDL2-2.0.9". Paste this folder in your C:\Program Files(x86)\ directory.
Copy the FindSDL2.cmake module and place it in a new "cmake" directory within your project. I found a FindSDL2.cmake file in the answer referenced in the Accepted Answer: https://brendanwhitfield.wordpress.com/2015/02/26/using-cmake-with-sdl2/
Find the SET(SDL2_SEARCH_PATHS line in the FindSDL2.cmake and add your copied development directory for SDL2 as a new line: "/Program Files (x86)/SDL2-2.0.9" # Windows
Within my CMakeLists.txt, add this line: set(CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake)
After this, running CMake worked for me. I'm including the rest of my CMakeLists just in case it further clarifies anything I may have left out:
cmake_minimum_required(VERSION 2.8.4)
project(Test_Project)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
# includes cmake/FindSDL2.cmake
set(CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake)
set(SOURCE_FILES src/main.cpp src/test.cpp)
add_executable(test ${SOURCE_FILES})
# The two lines below have been removed to run on my Windows machine
#INCLUDE(FindPkgConfig)
#PKG_SEARCH_MODULE(SDL2 REQUIRED sdl2)
find_package(SDL2 REQUIRED)
INCLUDE_DIRECTORIES(${SDL2_INCLUDE_DIR})
TARGET_LINK_LIBRARIES(chip8 ${SDL2_LIBRARY})
Hope this helps somebody in the near future.
by the time of my answer, SDL2 is provided with sdl2-config executable (as I understand, developers call him "experimental").
After "make install" of SDL2 you can try calling it from terminal with
sdl2-config --cflags --libs to see what it outputs.
And then you can add call to it in your makefile:
set(PROJECT_NAME SomeProject)
project(${PROJECT_NAME})
execute_process(COMMAND /usr/local/bin/sdl2-config --libs RESULT_VARIABLE CMD_RES OUTPUT_VARIABLE SDL2_CFLAGS_LIBS ERROR_VARIABLE ERR_VAR OUTPUT_STRIP_TRAILING_WHITESPACE)
message("SDL2_CFLAGS_LIBS=${SDL2_CFLAGS_LIBS}; CMD_RES=${CMD_RES}; ERR_VAR=${ERR_VAR}")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 ${SDL2_CFLAGS_LIBS}")
set(SOURCE_FILES main.cpp)
add_executable(${PROJECT_NAME} ${SOURCE_FILES})
Here I have a problem - if I only put an executable name without path like
execute_process(COMMAND sdl2-config --libs <...>
I get error "No such file", i.e. cmake does not search in current path and I don't know how to write it properly by now.
One more notice: in my makefile I do not user --cflags option, because cmake finds includes correctly and I do not need to specify them explicitly.
For your information, I was able to successfully cmake and compile SDL2_ttf while linking to SDL2 source code.
At first I was getting errors due to cmake not being able to locate SDL2, even though it was specified in cmake using the SLD2_DIR variable in cmake.
It seems that for some reason cmaking SDL2 fails to create the SDL2Targets.cmake file which is searched for by SDL2_ttf
If this is the case for you, get the SDL2Targets.cmake file from https://bugs.archlinux.org/task/57972 and modify the file like so:
You can remove the following lines:
get_filename_component(_IMPORT_PREFIX "${CMAKE_CURRENT_LIST_FILE}" PATH)
get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)
get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)
get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)
if(_IMPORT_PREFIX STREQUAL "/")
set(_IMPORT_PREFIX "")
endif()
and add this one:
set(_IMPORT_PREFIX "C:/SDL2-2.0.12")
Obviously change the filepath to the place you unpacked the SDL2 source code
I'm not sure if this is exactly your issue, but there it is.
I am currently using CMake to create a static library which utilizes a few of the static libraries from OpenCV 4 ( core imgcodecs video highgui imgproc ). My intention is to be able to bundle all of the required OpenCV static libraries into my own library so that I can distribute it as one library. Additionally, I want for the user of my library to not have to install OpenCV 4 on their system (but do not mind if the user has to do simple installs using apt-get install). I know there are tools for bundling static libraries (such as using ar for linux).
However, where I really am having the issue is with all the dependencies of OpenCV (such as libjpeg, libpng, etc). I don't necessarily mind if these libraries are bundled with mine or linked dynamically as they are relatively easy to install (can be installed with sudo apt-get install, whereas opencv4 needs to be built from source).
What is the best way to go about doing this?
This is my current CMakeLists.txt
It is currently working, but that is because I am using find_package(OpenCV REQUIRED) (which defeats the purpose of what I am trying to do). When I remove that line, the linker complains about not being able to find the OpenCV dependencies.
cmake_minimum_required(VERSION 2.8)
project(myproject)
set(CMAKE_CXX_STANDARD 14)
include_directories(${CMAKE_CURRENT_LIST_DIR}/include)
link_directories(${CMAKE_CURRENT_LIST_DIR}/lib)
find_package(OpenMP REQUIRED)
find_package(OpenCV REQUIRED)
set(JSON_BuildTests OFF CACHE INTERNAL "")
add_subdirectory(nlohmann_json)
list(APPEND LINKER_LIBS opencv_core opencv_highgui opencv_video opencv_imgcodecs libmxnet.so libncnn.a nlohmann_json::nlohmann_json)
file(GLOB SRC${CMAKE_CURRENT_LIST_DIR}/src/*.cpp${CMAKE_CURRENT_LIST_DIR}/main.cpp)
add_library(myproject ${SRC})
target_link_libraries(myproject ${LINKER_LIBS} ${OpenMP_CXX_FLAGS})
To elaborate on my question. I build my project which generates libmyproject.a. I then take this library and will eventually extract the symbols from the OpenCV libs (libopencv_core.a libopencv_highgui.a libopencv_imgcodecs.a libopencv_video.a) and add them to my lib (for the time being, I have not yet done this step, which is why in the below example I am linking libopencv_*). I then use my library in a new project, for which the CMakeLists.txt is shown below:
cmake_minimum_required(VERSION 2.8)
project(myproject-driver)
set(CMAKE_CXX_STANDARD 14)
include_directories(${CMAKE_CURRENT_LIST_DIR}/include)
link_directories(${CMAKE_CURRENT_LIST_DIR}/lib)
find_package(OpenMP REQUIRED)
add_executable(myproject-driver main.cpp)
target_link_libraries(myproject-driver myproject libncnn.a ${OpenMP_CXX_FLAGS} libmxnet.so libopencv_core.a libopencv_highgui.a libopencv_imgcodecs.a libopencv_video.a)
Building this generates the following errors:
Linking CXX executable myproject-driver
/usr/bin/ld: /home/nchafni/Cyrus/myproject/lib/libopencv_imgcodecs.a(grfmt_jpeg.cpp.o): undefined reference to symbol 'jpeg_default_qtables##LIBJPEG_8.0'
//usr/lib/x86_64-linux-gnu/libjpeg.so.8: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
How can I fix this. Is there some CMake command which will link all these dependencies for me? Do I need to manually track down each dependency of those libopencv_* libs and link those manually? Once again, this is assuming that the person using libmyproject.a can't use find_package(OpenCV REQUIRED) as it won't be defined as they have not installed OpenCV on their machine.
First of all, don't use the super old and outdated version 2.8 of CMake. CMake 3.x is so much more powerful and pretty straightforward to use.
Some tips for modern CMake.
Don't use file(GLOB), see here why that is.
Don't use directory wide instructions, rather use target instructions, e.g. target_include_directories vs. include_directories.
Don't use string variables like ${<PACKAGE_NAME>_LIBRARIES}, rather use targets, e.g. <Package_NAME>::lib
When using targets instead of string variables, all the properties (including LINK_INTERFACE) of that target will be populated to the library/executable when calling target_link_libraries, so no more include_directories,link_directories, etc.
myproject
cmake_minimum_required(VERSION 3.14)
project(myproject)
set(CMAKE_CXX_STANDARD 14)
find_package(OpenMP REQUIRED)
find_package(OpenCV REQUIRED)
set(JSON_BuildTests OFF CACHE INTERNAL "")
add_subdirectory(nlohmann_json)
set(SOURCES ...) # list all the source files here
add_library(myproject ${SOURCES})
target_include_directories(myproject PUBLIC # give it a scope
${CMAKE_CURRENT_LIST_DIR}/include
)
target_link_libraries(myproject PUBLIC # give it a scope
opencv_core # using the target, you will get all LINK_LIBRARIES
opencv_highgui
opencv_video
opencv_imgcodecs
libmxnet.so # where is this coming from?
libncnn.a # where is this coming from?
nlohmann_json::nlohmann_json
OpenMP::OpenMP_CXX ## linking against a target, CXX_FLAGS will be populated automatically
)
myprojec-driver
cmake_minimum_required(VERSION 3.14)
project(myproject-driver)
set(CMAKE_CXX_STANDARD 14)
add_executable(myproject-driver main.cpp)
target_link_libraries(myproject-driver PUBLIC # give it a scope
myproject # gets all dependencies through the LINK_INTERFACE
)