Trying to add libraries with CMake results in error - c++

I am trying to add an external .lib file to my project in Clion which uses CMake. My code is very simple and is simply to test whether the library gets included:
#include <iostream>
#include "header/test.h"
int main() {
test a; // returns error saying undefined reference to 'test::test()'
return 0;
}
When running this code I get the following error:
undefined reference to `test::test()'
This is because I am trying to make a test object however the library for test is not included.
The test.lib file and the test.h file are both in the "header" folder which is in the root of my project folder. The file path to this is F:\Project\header\
My Cmake text file is as follows:
cmake_minimum_required(VERSION 3.14)
project(Project)
set(CMAKE_CXX_STANDARD 14)
add_executable(Project main.cpp)
target_link_libraries(Project
F:\\Project\\header\\test.lib)
In the cmake text file i use the line:
target_link_libraries(Project F:\Project\header\test.lib)
This should include the library file, however it doesn't seem to because I get the "undefined reference to..." error as mentioned above. The Cmake compiler does not give me an error.

You are conceptually correct, however you are not doing it in the CMake fashion. Check out the following links on how to link an external library.
CMake link to external library
cmake doesn't support imported libraries?
https://gitlab.kitware.com/cmake/community/wikis/doc/tutorials/Exporting-and-Importing-Targets
For your case, it would be as follows):
cmake_minimum_required(VERSION 3.14)
project(Project)
set(CMAKE_CXX_STANDARD 14)
# Import the library into the CMake build system
ADD_LIBRARY(test SHARED IMPORTED)
# Specify the location of the library
SET_TARGET_PROPERTIES(TARGET test PROPERTIES IMPORTED_LOCATION “/path/to/lib/test.dll”)
# create the executable
add_executable(Project main.cpp)
# Link your exe to the library
target_link_libraries(Project test)
The CMake documentation is very good. I recommend checking it out when you run into issues.
https://cmake.org/cmake/help/latest/command/add_library.html#imported-libraries

Related

Using shared library created in a different directory

I've created a shared library with library.h and library.cpp. Then wrote a CMakeLists.txt file to build it as a shared library.
CMakeLists.txt
cmake_minimum_required(VERSION 3.10)
project(test_pro)
set(CMAKE_CXX_STANDARD 11)
add_library(test_pro SHARED library.cpp library.h)
after building the library, I was able to get a .so file as /home/user/projects/test_lib/bin/libtest_pro.so
Then I tried linking the created library to another project in /home/user/projects/testproject
CMakeLists.txt
cmake_minimum_required(VERSION 3.10)
project(testproject)
set(CMAKE_CXX_STANDARD 11)
link_directories(
/home/user/projects/test_lib/bin
)
add_executable(testproject main.cpp)
target_link_libraries (testproject test_pro)
It successfully builds the testproject (ldd command shows it has linked correctly), but I'm unable to use the library I've created in it.
In the main.cpp I've tried,
#include "library.h"
#include "test_pro"
#include <test_pro>
#include <test_pro/library.h>
But all the above gave build failures (fatal error: xxx: No such file or directory). How do I use this created library?
Just like you set link_directories() you have to specify include_directories(). And it is recommended not to use link_directories() at all, instead pass absolute path to the library into target_link_libraries().

How to correctly create a CMake file for a modular project

Suppose C++ project A as my main program and project B is my module that is shared object (.so). Project A consist source and headers that is common between both projects. Project A load module .so file in runtime.
Project A:
class-AI.cpp (It contains function funcA)
class-AI.h
class-AII.cpp
class-AII.h
class-AIII.cpp
class-AIII.h
main.cpp
Project B: (Shared Object)
class-BI.cpp (Its inherit from class-AI)
class-BI.h
With following CMake files both project build successfully.
Project A CMakefile:
cmake_minimum_required(VERSION 3.6)
project(ProjectA)
set(CMAKE_CXX_STANDARD 11)
set(SOURCE_FILES
main.cpp
class-AI.cpp
class-AI.h
class-AII.cpp
class-AII.h
class-AIII.cpp
class-AIII.h)
add_executable(ProjectA ${SOURCE_FILES})
set(EXECUTABLE_OUTPUT_PATH /opt/ProjectA/bin/)
Project B CMakefile:
cmake_minimum_required(VERSION 3.6)
project(ProjectB)
set(CMAKE_CXX_STANDARD 11)
set(SOURCE_FILES class-BI.cpp class-BI.h)
add_library(ProjectB SHARED ${SOURCE_FILES})
set_target_properties(ProjectB PROPERTIES
PREFIX ""
LIBRARY_OUTPUT_DIRECTORY /opt/ProjectA/bin/)
But at runtime Project A following error will be appear:
undefined symbol: _ZN6class-AI4funcAEv
How can I add dependency to project B correctly using CMake file and solve this error? (Actually I want to change my netbeans C++ project to Jetbrains CLion)
Thanks to Florian for his comment. My problem solved with adding this lines to Project A CMake file:
add_library(ProjectB SHARED IMPORTED GLOBAL)
set_target_properties(ProjectB PROPERTIES IMPORTED_LOCATION "/opt/ProjectA/bin/ProjectB.so")
target_link_libraries(ProjectA ProjectB)

Include Eigen library for Xcode project via CMake/CMakeLists.txt

I've got the following CMakeLists.txt (in my "project" folder) file for my project.
# define new project
PROJECT(SETUPMARKERTEST)
CMAKE_MINIMUM_REQUIRED(VERSION 2.8.0 FATAL_ERROR)
if(UNIX)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
endif(UNIX)
# Set static build for GLFW
SET(BUILD_SHED_LIBS OFF)
ADD_SUBDIRECTORY(ext/glfw-3.1.1)
# Set shared lib build for the rest
SET(BUILD_SHARED_LIBS ON)
# Find dependencies
SET(EIGEN_INCLUDE_DIR "${CMAKE_SOURCE_DIR}/ext/Eigen-3.1.2")
FIND_PACKAGE(OpenCV REQUIRED)
# Set header and source files
SET(MAR_Test_SOURCES
src/main.cpp
src/MarkerTracker.h src/MarkerTracker.cpp
src/PoseEstimation.h src/PoseEstimation.cpp
)
# define executable
ADD_EXECUTABLE(${PROJECT_NAME} ${MAR_Test_SOURCES})
# define additional include directories and linking targets
INCLUDE_DIRECTORIES("ext/glfw-3.1.1/include" ${EIGEN_INCLUDE_DIR} ${OpenCV_INCLUDE_DIRS})
TARGET_LINK_LIBRARIES(${PROJECT_NAME} ${OpenCV_LIBS} glfw ${OPENGL_glu_LIBRARY} ${GLFW_LIBRARIES})
And my Eigen folder is in "project/ext/Eigen/3.1.2/Eigen/".
Somehow when I created my project for Xcode (in "project/buildXcode/" with Cmake .. -G "Xcode") and run it, Xcode throws me the error:
So I guess there is some error in my CMakeLists.txt, unfortunately I received that file and I'm new to CMake and thus didn't write it on my own nor am I very skilled with CMake.
Do you know what causes the error and can you fix the CMakeLists.txt that my project runs with the Eigen library?
Unfortunately it looks like windows is having no problem with this, whereas mac is bleating.
You just have to use
#include <Eigen/Dense>
instead of
#include <Eigen\Dense>
...pretty stupid error.

Cannot find library with simple C++ example

I am building a C++ library called alpha in Ubuntu with cmake, which contains one source file:
cmake_minimum_required(VERSION 2.8)
project(Alpha)
add_library (alpha alpha.cpp)
This creates a file called libalpha.a, which I now want to link to. So, I copy it into the source directory of another C++ projected called beta, which also contains one source file:
cmake_minimum_required(VERSION 2.8)
project(Beta)
add_executable(beta beta.cpp)
target_link_libraries(beta alpha)
However, I get the following error:
/usr/bin/ld: cannot find -lalpha
The same thing happens if I use the line:
target_link_libraries(beta libalpha.a)
Why can beta not find the alpha library?
If you wish to build the library and the program completely separately, you have to use imported targets. When you try to link your executable against a "completely unknown" library, CMake build system automatically passes the task of locating the library to the linker, simply adding -lalpha option. When the linker encounters the option it attempts to locate libalpha.so in one of the standard library locations (i.e. /usr/lib/, /usr/local/lib etc) and expectedly fails. You can use an absolute path to the libalpha.a: target_link_libraries(beta /path/to/libalpha.a).
However if you can build things together, this greatly simplifies the task. Consider
<project>/CMakeLists.txt:
cmake_minimum_required(VERSION 2.8)
Project(Test)
add_subdirectory(alpha)
add_subdirectory(beta)
<project>/alpha/CMakeLists.txt
cmake_minimum_required(VERSION 2.8.11)
project(alpha)
set(SOURCES alpha.c)
add_library(alpha ${SOURCES})
target_include_directories(
alpha INTERFACE
"$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>"
"$<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}>"
)
target_include_directories() with the complex expression within is required to automatically add libalpha include directories to all components which later are linked against libalpha.
<project>/beta/CMakeLists.txt
project(beta)
set(SOURCES beta.c)
add_executable(beta ${SOURCES})
target_link_libraries(beta alpha)
Add this line with the path to alpha-library.
link_directories( <library path> )

linking glbinding with cmake

I'm trying to use glbinding in my own project. I'm using cmake to build everything. The problem is linker cannot find this library. Probably I don't build library thus it cannot be linked, but I don't know how to achive that.
I've written linking code according to https://github.com/hpicgs/glbinding#linking-binaries.
Cmake:
set(SOURCE_FILES main.cpp)
add_executable(AKOpenGLEngine ${SOURCE_FILES})
set(CMAKE_PREFIX_PATH ${CMAKE_MODULE_PATH} glbinding )
find_package(glbinding REQUIRED)
include_directories(${GLBINDING_INCLUDES})
target_link_libraries(AKOpenGLEngine glbinding ${GLBINDING_LIBRARIES})
Error:
Linking CXX executable AKOpenGLEngine
ld: library not found for -lglbinding
main.cpp:
#include <glbinding/gl/gl.h>
int main(void) {
glbinding::Binding::initialize();
exit(EXIT_SUCCESS);
}
My current project structure:
Have you tried to remove the glbinding from target_link_libraries? ${GLBINDING_LIBRARIES} should be sufficient; it passes <your_specific_file_path_to_glbinding_library> to the linker. With -lglbinding the linker searches for a library within some default directories, your glbinding or build directory not included, thus throwing a library not found. To verify the content of ${GLBINDING_LIBRARIES} you can print it to cmake output, e.g., via message(STATUS ${GLBINDING_LIBRARIES}). However, i also suggest to integrate glbinding as external project as suggested by #janisz.
EDIT: sorry, didn't see the valid, but collapsed answer of #jet47