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How to Generate Included Files Using Cmake?

4 minutes read

When using CMake to generate included files, you can use the configure_file command to generate files with predefined content and variables. This command allows you to create new files by copying an existing one and substituting variables within it. By setting up a template file with placeholders for variables, CMake can then generate the included files by filling in those placeholders with the specified values during the configuration process. This approach is particularly useful for generating header files containing constants or configurations, allowing for easy customization and maintenance.


What is the purpose of the CMake tool?

CMake is a cross-platform build system that is designed to build, test, and package software projects. Its purpose is to simplify the build process by generating platform-specific build files (such as makefiles or project files) based on a single, platform-independent configuration file. This allows developers to write their build scripts in a simple and portable way while generating the appropriate build system for their specific platform. CMake is commonly used in C and C++ projects but can be used with other programming languages as well.


What is a CMake target?

A CMake target refers to an executable, library, or custom command that can be built using the CMake build system. Targets are specified in a CMakeLists.txt file and define the source files, compile options, and dependencies required to build the specified target. Targets provide a way to organize and manage the building process of a project in CMake.


What is the purpose of CMake cache?

The purpose of CMake cache is to store build configuration settings and variables that were set by the user during the CMake configure process. This allows the user to easily modify and update the build configuration without having to redo the configuration from scratch. The cache also allows for easier collaboration and reproducibility of builds across different environments.


How to use CMake to build a project with multiple subdirectories?

To use CMake to build a project with multiple subdirectories, follow these steps:

  1. Create a top-level CMakeLists.txt file in the root directory of your project. This file will be used to define the project and specify the subdirectories.
  2. In the top-level CMakeLists.txt file, use the add_subdirectory() command to add each of the subdirectories to the project. For example, if you have two subdirectories named src and lib, you would add the following lines to the top-level CMakeLists.txt file: 
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add_subdirectory(src)
add_subdirectory(lib)


  1. In each subdirectory, create a CMakeLists.txt file that specifies the build instructions for that particular directory. This may include defining targets, setting compiler flags, or including external libraries.
  2. Run CMake to generate the build system files for your project. You can do this by running the following commands in the root directory of your project: 
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mkdir build
cd build
cmake ..


This will create the necessary build files for your project in the build directory.

  1. Build your project using the build system files generated by CMake. This can be done by running the following commands in the build directory:
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cmake --build .


This will build all targets specified in the CMakeLists.txt files in your project's subdirectories.


By following these steps, you can use CMake to build a project with multiple subdirectories. Each subdirectory can have its own build instructions, allowing for a modular and organized project structure.


What is the CMakeLists.txt file structure?

The CMakeLists.txt file is used in CMake, a build system generator tool, to define how a project should be built. The general structure of a CMakeLists.txt file includes:

  1. Project name and version: This is typically declared at the beginning of the file using the project() command.
  2. Minimum required CMake version: This is specified using the cmake_minimum_required() command.
  3. Add subdirectories: Additional directories containing CMakeLists.txt files can be added using the add_subdirectory() command.
  4. Add executable or library targets: Executables or libraries can be defined using the add_executable() or add_library() commands.
  5. Link libraries: External libraries or dependencies can be linked to the project using the target_link_libraries() command.
  6. Set compiler flags: Compiler flags can be set using the target_compile_options() command.
  7. Set include directories: Include directories can be specified using the target_include_directories() command.
  8. Define installation rules: Installation rules for built targets can be defined using the install() command.
  9. Miscellaneous commands: Other CMake commands may be used to customize the build process as needed.


Overall, the CMakeLists.txt file serves as a blueprint for how the project should be built and organized.


How to specify compiler flags in CMake?

To specify compiler flags in CMake, you can use the add_compile_options or set(CMAKE_CXX_FLAGS) commands in your CMakeLists.txt file.


Here is an example of how you can specify compiler flags using add_compile_options:

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add_compile_options(-Wall -Wextra)


This will add -Wall and -Wextra flags to the compilation process.


If you want to set specific flags for a certain build configuration (e.g. Debug, Release), you can use the following syntax:

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set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -Wall -Wextra")
set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O3")


This will add -Wall -Wextra flags for the Debug configuration and -O3 flag for the Release configuration.


Remember to always check the documentation of your compiler to ensure that you are using the correct compiler flags.

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