YouTipCmake Advanced Features
Title: CMake Advanced Features | Rookie Tutorial
CMake advanced features allow us to more flexibly manage and configure CMake projects to meet complex build requirements and environments.
This article will explain from the following aspects:
1. **Custom CMake Modules and Scripts**: Create custom modules and scripts to simplify the build process.
2. **Build Configuration and Targets**: Use multi-configuration generators and define multiple build targets.
3. **Advanced Finding and Configuration**: Flexibly find packages and configure build options.
4. **Generate Custom Build Steps**: Add custom commands and targets to perform additional build operations.
5. **Cross-platform and Cross-compilation**: Support building for different platforms and cross-compilation.
6. **Target Properties and Configuration**: Set and modify target properties to meet specific requirements.
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## 1γCustom CMake Modules and Scripts
### 1.1 Custom CMake Modules
CMake allows you to create and use custom modules to simplify common build tasks.
Custom modules typically contain custom CMake scripts and functions.
**Creating Custom Modules:**
* Create a `cmake/` directory under the project directory to store custom CMake modules.
* Create a `MyModule.cmake` file under the `cmake/` directory.
* Include the custom module in the `CMakeLists.txt` file:
```cmake
list(APPEND CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake")
include(MyModule)
* `list(APPEND CMAKE_MODULE_PATH ...)` is used to extend CMake's module search path.
* `include(MyModule)` is used to load and execute the specified CMake module file.
**Custom Module Example (MyModule.cmake):**
## Example
```cmake
function(my_custom_function)
message(STATUS "This is a custom function!")
endfunction()
Call the custom function in CMakeLists.txt:
```cmake
my_custom_function()
### 1.2 Using Custom CMake Scripts
Custom CMake scripts allow you to execute custom configuration operations and flexibly handle complex build requirements.
**Creating Custom Scripts:**
* Create a script file in the project (e.g., `config.cmake`).
* Write CMake directives in the script.
Call the script in the CMakeLists.txt file:
```cmake
include(${CMAKE_SOURCE_DIR}/config.cmake)
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## 2γBuild Configuration and Targets
### 2.1 Multi-Configuration Generators
CMake supports multiple build configurations (such as Debug, Release).
Multi-configuration generators allow you to generate builds with different configurations in the same build directory.
**Specifying Configuration Type**
Set the default configuration in CMakeLists.txt:
```cmake
set(CMAKE_BUILD_TYPE "Release" CACHE STRING "Build type")
Using Visual Studio:
Select the build configuration (Debug or Release) in Visual Studio.
### 2.2 Build Targets
You can define multiple build targets, each with different build settings and options.
Adding multiple targets:
```cmake
add_executable(MyExecutable1 src/main1.cpp)
add_executable(MyExecutable2 src/main2.cpp)
Setting target properties:
```cmake
set_target_properties(MyExecutable1 PROPERTIES COMPILE_DEFINITIONS "DEBUG")
set_target_properties(MyExecutable2 PROPERTIES COMPILE_DEFINITIONS "RELEASE")
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## 3γAdvanced Finding and Configuration
### 3.1 Advanced Usage of Finding Packages
The `find_package()` instruction can be used to find and configure complex third-party libraries and packages.
Advanced options for finding packages:
```cmake
find_package(Boost REQUIRED COMPONENTS filesystem system)
Setting search paths:
```cmake
set(BOOST_ROOT "/path/to/boost")
find_package(Boost REQUIRED)
### 3.2 Configuration Files and Build Options
You can control build options and configuration through CMake configuration files.
Configuring options:
```cmake
configure_file(config.h.in config.h)
Configuration file (config.h.in):
```c
#define VERSION "@PROJECT_VERSION@"
Include the configuration file in source files:
```c
#include "config.h"
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## 4γGenerating Custom Build Steps
### 4.1 Custom Commands
CMake allows you to add custom build commands to execute additional operations during the build process.
Adding custom commands:
```cmake
add_custom_command( OUTPUT ${CMAKE_BINARY_DIR}/generated_file.txt
COMMAND ${CMAKE_COMMAND} -E echo "Generating file" > ${CMAKE_BINARY_DIR}/generated_file.txt
DEPENDS ${CMAKE_SOURCE_DIR}/input_file.txt )
Adding custom targets:
```cmake
add_custom_target(generate_file ALL DEPENDS ${CMAKE_BINARY_DIR}/generated_file.txt )
### 4.2 Custom Targets
Custom targets can be used to execute custom build steps, such as generating code, processing resources, etc.
Creating custom targets:
```cmake
add_custom_target(my_target COMMAND ${CMAKE_COMMAND} -E echo "Running custom target" DEPENDS some_dependency )
Executing targets during build:
```bash
cmake --build . --target my_target
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## 5γCross-platform and Cross-compilation
### 5.1 Cross-platform Building
CMake supports multi-platform building, allowing you to generate appropriate build files for different operating systems.
Specifying the platform:
```bash
cmake -DCMAKE_SYSTEM_NAME=Linux ..
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