Modern CMake By Example

知识点总结

0_helloworld

name: dependencies
	commands

hello: main.cpp
	$(CXX) -o hello main.cpp # CXX 是 Make 的内置变量
	echo "OK"

$ make hello
$ ./hello

1_helloworld

CC := clang
CXX := clang++ # 可通过 make CXX=g++ 形式覆盖
objects := main.o

hello: $(objects)
	$(CXX) -o $@ $(objects) # $@ 是自动变量,表示 target 名
main.o: main.cpp
	$(CXX) -c main.cpp

2_ask_for_answer

objects := main.o answer.o
answer: $(objects)
	$(CXX) -o $@ $(objects)
main.o: answer.hpp
answer.o: answer.hpp

4_switch_to_cmake

cmake_minimum_required(VERSION 3.9)
project(answer)
add_executable(answer main.cpp answer.cpp)

cmake -B build # 生成构建目录,-B 指定生成的构建系统代码放在 build 目录
cmake --build build # 执行构建
./build/answer # 运行 answer 程序

5_split_library

add_library(libanswer STATIC answer.cpp)

add_executable(answer main.cpp)
target_link_libraries(answer libanswer)

6_subdirectory

.
├── answer
│ ├── answer.cpp
│ ├── CMakeLists.txt
│ └── include
│ └── answer
│ └── answer.hpp
├── CMakeLists.txt
└── main.cpp

# CMakeLists.txt
add_subdirectory(answer)
add_executable(answer_app main.cpp)
target_link_libraries(answer_app libanswer) # libanswer 在 answer 子目录中定义

# answer/CMakeLists.txt
add_library(libanswer STATIC answer.cpp)
target_include_directories(libanswer PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include)

7_use_libcurl

find_package(CURL REQUIRED)
target_link_libraries(libanswer PRIVATE CURL::libcurl)

8_link_libs_in_same_root

# CMakeLists.txt
add_subdirectory(answer)
add_subdirectory(curl_wrapper)
add_subdirectory(wolfram)

# answer/CMakeLists.txt
add_library(libanswer STATIC answer.cpp)
target_include_directories(libanswer PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include)
target_link_libraries(libanswer PRIVATE wolfram)

# wolfram/CMakeLists.txt
add_library(wolfram STATIC alpha.cpp)
target_include_directories(wolfram PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include)
target_link_libraries(wolfram PRIVATE curl_wrapper)

# curl_wrapper/CMakeLists.txt
find_package(CURL REQUIRED)
add_library(curl_wrapper STATIC curl_wrapper.cpp)
target_include_directories(curl_wrapper
 PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include)
target_link_libraries(curl_wrapper PRIVATE CURL::libcurl)

9_cache_string

Cache 变量

set(WOLFRAM_APPID "" CACHE STRING "WolframAlpha APPID")

set(ENABLE_CACHE OFF CACHE BOOL "Enable request cache")
option(ENABLE_CACHE "Enable request cache" OFF) # 和上面基本等价

cmake -B build -DWOLFRAM_APPID=xxx

target_compile_definitions

target_compile_definitions(libanswer PRIVATE WOLFRAM_APPID="${WOLFRAM_APPID}")

10_interface_library

add_library(libanswer INTERFACE)
target_include_directories(libanswer INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/include)
target_compile_definitions(libanswer INTERFACE WOLFRAM_APPID="${WOLFRAM_APPID}")
target_link_libraries(libanswer INTERFACE wolfram)

11_target_compile_features

target_compile_features(libanswer INTERFACE cxx_std_20)

12_testing

CTest

# CMakeLists.txt
cmake_minimum_required(VERSION 3.14) # 提高了 CMake 版本要求
project(answer)
if(CMAKE_PROJECT_NAME STREQUAL PROJECT_NAME)
 include(CTest)
endif()

# answer/CMakeLists.txt
if(BUILD_TESTING)
 add_subdirectory(tests)
endif()

# answer/tests/CMakeLists.txt
add_executable(test_some_func test_some_func.cpp)
add_test(NAME answer.test_some_func COMMAND test_some_func)

$ ctest --test-dir build -R "^answer."

FetchContent

include(FetchContent)
FetchContent_Declare(
 catch2 # 建议使用全小写
 GIT_REPOSITORY https://github.com/catchorg/Catch2.git
 GIT_TAG v3.0.0-preview3)
FetchContent_MakeAvailable(catch2)
target_link_libraries(test_some_func} PRIVATE Catch2::Catch2WithMain)

FetchContent_GetProperties(catch2)
if(NOT catch2_POPULATED)
 FetchContent_Populate(catch2)
 add_subdirectory(${catch2_SOURCE_DIR} ${catch2_BINARY_DIR})
endif()

Macro & Function

macro(answer_add_test TEST_NAME)
 add_executable(${TEST_NAME} ${ARGN}) # ${ARGN} 类似于 C/C++ 中的 __VA_ARGS__
 add_test(NAME answer.${TEST_NAME} COMMAND ${TEST_NAME})
 target_link_libraries(${TEST_NAME} PRIVATE libanswer)
 target_link_libraries(${TEST_NAME} PRIVATE Catch2::Catch2WithMain)
endmacro()
answer_add_test(test_check_the_answer test_check_the_answer.cpp)
answer_add_test(test_another_function test_another_function.cpp)

13_back_to_makefile

WOLFRAM_APPID :=
.PHONY: build configure run test clean
build: configure
	cmake --build build
configure:
	cmake -B build -DWOLFRAM_APPID=${WOLFRAM_APPID}
run:
	./build/answer_app
test:
	ctest --test-dir build -R "^answer."
clean:
	rm -rf build

$ make build WOLFRAM_APPID=xxx
$ make test
$ make run
$ make clean

补充

直播时的 Q&A

CMake 是怎么找到 .cpp 文件依赖的头文件的?

模块依赖图是人工画的还是自动生成的?

在 CMakeLists.txt 里定义变量并检查要求不为空,会导致 VSCode 乱报错吗?

FetchContent 每次编译都要重新编译一遍依赖库吗?

能来个 VSCode 插件推荐列表吗?

扩展阅读

Makefile

CMake