How to Use Check_library_exists In Cmake?

In CMake, the check_library_exists function is used to check whether a specific library is available on the system. This function takes the following arguments: the library name, a list of symbols that need to be present in the library, a variable to store the result, and an optional variable to specify additional flags that should be added when linking against the library.

Here is an example of how check_library_exists can be used in a CMake script:

1
2
3
4
5
6

check_library_exists(m library_function RESULT_VAR)
if(${RESULT_VAR})
  message("Library found")
else()
  message("Library not found")
endif()

In this example, check_library_exists checks whether the function library_function is present in the library m. The result of the check is stored in the variable RESULT_VAR, which is then used to display a message indicating whether the library was found or not.

Overall, check_library_exists is a useful CMake function for checking the presence of libraries on the system and can be used to adjust the build configuration based on the availability of specific libraries.

What is CMake architecture?

CMake is a cross-platform build system that generates build files based on a set of build instructions defined in configuration files. Its architecture consists of several key components:

1. CMake language: CMake uses its own scripting language to define how a project should be built. This language allows developers to specify build options, dependencies, compiler flags, and other build-related configurations.
2. CMakeLists.txt files: CMake projects are typically organized into different directories, each containing a CMakeLists.txt file. These files define the source files and build targets for that directory, as well as any configuration options specific to that directory.
3. Generators: CMake supports the generation of build files for different build systems, such as Makefiles, Visual Studio solutions, and Xcode projects. These generators are responsible for converting the build instructions defined in the CMake configuration files into a format that the target build system can understand.
4. CMake cache: CMake maintains a cache of build options and variables that can be set by the user or detected automatically by CMake. This cache allows developers to customize the build process without having to modify the configuration files directly.
5. Dependency resolution: CMake automatically handles resolving dependencies between different targets in the build process. This helps ensure that dependencies are built in the correct order and that build artifacts are properly linked together.

Overall, CMake's architecture is designed to provide a flexible and efficient build system that can be easily adapted to a wide range of project types and build environments.

How to include external libraries in CMake?

To include external libraries in CMake, you can use the find_package() command to search for the library on your system. Once the library is found, you can use the target_link_libraries() command to link the library to your project.

Here's an example of how to include the Boost library in your CMake project:

1. Find the Boost package:

1

find_package(Boost REQUIRED COMPONENTS system filesystem)

1. Link the Boost libraries to your project:

1

target_link_libraries(your_project_name Boost::system Boost::filesystem)

Make sure to replace your_project_name with the actual name of your project.

You can also specify the path to the external library manually using the include_directories() command and the link_directories() command. For example, if you have a library installed in a custom location, you can include it like this:

1
2
3

include_directories(/path/to/library/include)
link_directories(/path/to/library/lib)
target_link_libraries(your_project_name library_name)

Replace /path/to/library/include and /path/to/library/lib with the actual paths to the library header files and library files, respectively. Replace library_name with the actual name of the library.

What is the target_compile_features command in CMake?

The target_compile_features command in CMake is used to specify the required features or language standards that are needed to build a particular target (e.g., executable, library). It can be used to ensure that the compiler supports the necessary language features before attempting to build the target. This command allows you to specify a list of features or language standards that are required for building the target, and CMake will automatically set the appropriate compiler flags to enable those features.

How to set CMake variables?

CMake variables can be set in the CMakeLists.txt file using the set() command. Here's an example of how to set a variable in CMake:

1

set(MY_VARIABLE "Hello, World!")

This will set the variable MY_VARIABLE to the value "Hello, World!". You can then use this variable in other parts of your CMakeLists.txt file by referencing it using the ${} syntax, like so:

1

message("My variable contains: ${MY_VARIABLE}")

This will print out "My variable contains: Hello, World!" when CMake is run. You can also set variables conditionally based on certain conditions using if statements, or set them to the result of a function call. There are many different ways to set variables in CMake, so be sure to consult the CMake documentation for more advanced use cases.

What is the target_link_libraries command in CMake?

The target_link_libraries command in CMake is used to specify the libraries that a target executable or library depends on. This command adds the specified libraries as dependencies to the target, ensuring that they are linked during the build process. This command is typically used in CMakeLists.txt files to link external libraries to the target.

How to run CMake from the command line?

To run CMake from the command line, you can follow these steps:

1. Open a terminal or command prompt on your system.
2. Navigate to the directory where your CMake project is located using the cd command.
3. Once you are in the project directory, you can run CMake by using the following command:

1

cmake <path_to_CMakeLists.txt>

Replace <path_to_CMakeLists.txt> with the path to your CMakeLists.txt file. This file contains the configuration information for your CMake project.

1. After running the cmake command, CMake will generate the necessary build files for your project based on the configuration defined in the CMakeLists.txt file.
2. You can then proceed to build your project using the appropriate build system (e.g., make, Visual Studio, etc.) by running the corresponding build command in the terminal, for example:

1

make

This will compile your project and generate the executable file.

That's it! You have successfully run CMake from the command line for your project.