概 述
CMake中经常使用set()命令来设置一些CMake变量，本文介绍一些常用变量的含义。
变量含义
1. CMAKE_CXX_STANDARD
设置C++标准
set(CMAKE_CXX_STANDARD 11)
# set(CMAKE_CXX_STANDARD 14)
# set(CMAKE_CXX_STANDARD 17)
2. CMAKE_UNITY_BUILD
设置开启元编译，于CMAKE_UNITY_BUILD_BATCH_SIZE配合使用，用于加速项目编译速度，参考。
# 全局设置
set(CMAKE_UNITY_BUILD ON)
# 设置元编译的batch大小
set(CMAKE_UNITY_BUILD_BATCH_SIZE 16)
# 单个目标
set_target_properties(<target> PROPERTIES UNITY_BUILD ON)
3. CMAKE_BUILD_TYPE
设置单个配置生成器上的编译类型，例如Makefile等
# set(CMAKE_BUILD_TYPE "Debug")
set(CMAKE_BUILD_TYPE "Release")
4. CMAKE_CONFIGURATION_TYPES
设置多配置生成器上的可用编译类型，例如Visual Studio、Xcode等
set(CMAKE_CONFIGURATION_TYPES "Release;Debug")
5. CMAKE_<LANG>_FLAGS
设置对应语言的编译选项，以C++为例，
-
CMAKE_CXX_FLAGS：设置C++编译选项 -
CMAKE_CXX_FLAGS_DEBUG：设置C++ Debug 编译选项 -
CMAKE_CXX_FLAGS_RELEASE：设置C++ Relese 编译选项
6. BUILD_USE_64BITS
设置使用64位编译
set(BUILD_USE_64BITS ON)
7. BUILD_SHARED_LIBS
设置是否生成动态库，默认是开启状态，根据add_library()生成对应的动态库
# set(BUILD_SHARED_LIBS ON)
set(BUILD_SHARED_LIBS OFF)
8. CMAKE_*_OUTPUT_DIRECTORY
设置输出目录
# 全局设置
set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
# 单个目标
set_target_properties( targets...
PROPERTIES
ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib"
LIBRARY_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib"
RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin"
)
9. CMAKE_<CONFIG>_POSTFIX
设置文件后缀
# 全局设置
set(CMAKE_DEBUG_POSTFIX "_debug")
set(CMAKE_RELEASE_POSTFIX "_release")
# 单个目标
set_target_properties( targets...
PROPERTIES
DEBUG_POSTFIX "_debug"
RELEASE_POSTFIX "_release"
)
