文章目录
- 1. Basic Cmake Based Project
- 2. Executable VS Library
- 3. Every module has its own CMakeList.txt in its folder
-
- 4. 强制以Debug, Release, RelWithDebInfo, MinSizeRel其中一种作为编译方式
-
- 5. CMake高频常用变量
- 7. 在CMake里打印信息
转自 链接：
https://www.jianshu.com/p/622d2ec351b5
1. Basic Cmake Based Project
cmake_minimum_required(VERSION 3.16.0)
project(helloworld VERSION 1.0.0 LANGUAGES CXX)
set(CMAKE_PREFIX_PATH $ENV{QT_DIR})
set(CMAKE_INCLUDE_CURRENT_DIR ON)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)
set(CMAKE_AUTOUIC ON)
find_package(Qt6 COMPONENTS Core Qml Quick LinguistTools REQUIRED)
set(TS_FILES TestApp_zh_CN.ts TestApp_en_US.ts)
aux_source_directory(src SRC_LIST)
qt6_add_resources(QML_QRC qml_module_a.qrc qml_module_b.qrc)
set(PROJECT_SOURCES ${SRC_LIST} ${TS_FILES} ${QML_QRC})
add_executable(${CMAKE_PROJECT_NAME} WIN32 ${PROJECT_SOURCES})
qt_create_translation(QM_FILES ${CMAKE_SOURCE_DIR} ${TS_FILES})
target_compile_definitions(${CMAKE_PROJECT_NAME} PRIVATE $<$<OR:$<CONFIG:Debug>,$<CONFIG:RelWithDebInfo>>:QT_QML_DEBUG>)
target_link_libraries(${CMAKE_PROJECT_NAME} PRIVATE
Qt6::Core
Qt6::Qml
Qt6::Quick)
qt_import_qml_plugins(${CMAKE_PROJECT_NAME})
2. Executable VS Library
add_executable(${CMAKE_PROJECT_NAME} ${SRC_LIST})
add_library(${CMAKE_PROJECT_NAME} [STATIC|SHARED|MODULE] ${SRC_LIST})
3. Every module has its own CMakeList.txt in its folder
3.1 不推荐的做法：
aux_source_directory(. DIR_SRCS1)
aux_source_directory(. DIR_SRCS2)
aux_source_directory(. DIR_SRCS3)
add_executable(${CMAKE_PROJECT_NAME} ${DIR_SRCS1} ${DIR_SRCS2} ${DIR_SRCS3})
这种做法会导致项目里即便改了一处代码，也会编译所有代码，导致编译时间较长，不能很好利用增量编译，再说C/C++本身编译就很慢
3.2 推荐的做法
以下以一个开源项目live555改版成为cmake项目作为推荐的项目代码组织结构的案例，虽然最终目标是编译成Library给外部使用，但内部同时也包含了打包成可执行文件的模块(mediaServer)：
├── CMakeLists.txt
├── BasicUsageEnvironment
│ └── CMakeLists.txt
│ └── BasicHashTable.cpp
│ └── xxx.cpp
│ └── include
│ └── BasicHashTable.hh
│ └── xxx.hh
├── groupsock
│ └── CMakeLists.txt
│ └── GroupEId.cpp
│ └── xxx.cpp
│ └── include
│ └── GroupEId.hh
│ └── xxx.hh
├── liveMedia
│ └── CMakeLists.txt
│ └── AC3AudioRTPSink.cpp
│ └── xxx.cpp
│ └── include
│ └── GroupEId.hh
│ └── xxx.hh
├── mediaServer
│ └── CMakeLists.txt
│ └── DynamicRTSPServer.cpp
│ └── xxx.cpp
└── UsageEnvironment
└── CMakeLists.txt
└── HashTable.cpp
└── xxx.cpp
└── include
└── Boolean.hh
└── xxx.hh
其中，BasicUsageEnvironment, groupsock, liveMedia, UsageEnvironment都是live555项目的子模块，mediaServer是集成所有子模块打包成为可执行文件的部分。
作为项目入口，推荐的CMakeList.txt可以如下：
cmake_minimum_required(VERSION 3.15)
project(live555 LANGUAGES CXX)
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
ADD_SUBDIRECTORY(UsageEnvironment)
ADD_SUBDIRECTORY(BasicUsageEnvironment)
ADD_SUBDIRECTORY(groupsock)
ADD_SUBDIRECTORY(liveMedia)
ADD_SUBDIRECTORY(mediaServer)
模块内部CMakeList.txt推荐如下：
project(BasicUsageEnvironment)
include_directories(../UsageEnvironment/include)
include_directories(../groupsock/include)
include_directories(./include)
aux_source_directory(./ SRC_LIST)
add_library(${PROJECT_NAME} STATIC ${SRC_LIST})
作为目标是编译为可执行文件的CMakeList.txt如下：
project(mediaServer)
include_directories(../UsageEnvironment/include)
include_directories(../groupsock/include)
include_directories(../liveMedia/include)
include_directories(../BasicUsageEnvironment/include)
# 当前目录下也有代码
aux_source_directory(. SRC_LIST)
# 当前模块是main入口，最终目标是编译出live555的可执行文件，因此不再用add_library()
add_executable(${PROJECT_NAME} ${SRC_LIST})
# 链接所有其他模块到当前模块
target_link_libraries(${PROJECT_NAME} PRIVATE
liveMedia
groupsock
BasicUsageEnvironment
UsageEnvironment)
4. 强制以Debug, Release, RelWithDebInfo, MinSizeRel其中一种作为编译方式
方法一：
在工程build目录下执行
cmake .. -DCMAKE_BUILD_TYPE=Debug|Release|MinSizeRel|RelWithDebInfo
方法二:
或者在顶级CMakeList.txt里加入:
set(CMAKE_BUILD_TYPE Debug|Release|MinSizeRel|RelWithDebInfo)
5. CMake高频常用变量
变量的引用方式是使用${}，在IF中，不需要使用这种方式，直接使用变量名亦可
自定义变量：SET(OBJ_NAME xxxx)，调用自定义变量： ${OBJ_NAME}
设置环境变量: SET(ENV{NAME} value), 需要注意的是这里ENV没有$; 调用环境变量: $ENV{NAME}
CMAKE的常用变量：
| 变量 | 意义 |
|---|
CMAKE_SOURCE_DIR | 工程项目跟目录 |
CMAKE_CURRENT_SOURCE_DIR | CMakeList.txt所在的目录 |
CMAKE_MODULE_PATH | 如果工程复杂，可能需要编写一些cmake模块，这里通过SET指定这个变量 |
LIBRARY_OUTPUT_DIR | 库最终存放目录 |
BINARY_OUTPUT_DIR | 可执行的最终存放目录 |
PROJECT_NAME | 当前CMakeList.txt里设置的project_name |
CMAKE_PROJECT_NAME | 项目跟目录配置的project_name |
# 6. 在CMake里区分操作系统
if(CMAKE_SYSTEM_NAME MATCHES "Linux") // 注意区分大写
message(STATUS "Linux platorm!")
elseif(CMAKE_SYSTEM_NAME MATCHES "Windows")
if(CMAKE_CL_64)
message(STATUS "Windows Win64 platform!")
else()
message(STATUS "Windows Win32 platform!")
endif(CMAKE_CL_64)
elseif(CMAKE_SYSTEM_NAME MATCHES "FreeBSD")
message(STATUS "FreeBSD platform!")
else()
message(STATUS "other platform!")
endif(CMAKE_SYSTEM_NAME MATCHES "Linux")
简化版亦可:
if (WIN32)
message(STATUS "Now is windows")
elseif (APPLE)
message(STATUS "Now is Apple systens.")
elseif (UNIX)
message(STATUS "Now is UNIX-like OS's.")
endif ()
7. 在CMake里打印信息
message([STATUS|WARNING|AUTHOR_WARNING|FATAL_ERROR|SEND_ERROR] "message to display" ...)
(无) = 重要消息
STATUS = 非重要消息
WARNING = CMake 警告, 会继续执行
AUTHOR_WARNING = CMake 警告 (dev), 会继续执行
SEND_ERROR = CMake 错误, 继续执行，但是会跳过生成的步骤
FATAL_ERROR = CMake 错误, 终止所有处理过程
一般用于排错打印日志，或者打印编译过程信息及步骤
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