cmake使用

[hujianglang]

参考：https://github.com/richardchien/modern-cmake-by-example

Modern CMake by Example:

hello:main.cpp
$(CXX) -o hello main.cpp
echo "OK"
注释：
target:hello

make CC=gcc CXX=g++ clean
make CC=gcc CXX=g++ answer

example1:
CMakeLists.txt:

cmake_minimum_required(VERSION 3.9)
project(answer)
set(WOLFRAM_APPID
"" CACHE STRING "WolframAlpha APPID")

if(WOLFRAM_APPID STREQUAL "")
message(SEND_ERROR "WOLFRAM_APPID must not be empty")

endif()

#添加answer子目录
add_subdirectory(answer)
add_subdirectory(curl__wrapper)

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

#添加库目标，static指定为静态库
add_library(libanswer STATIC answer.cpp)

message(STATUS "current source dir: ${CMAKE_CURRENT_SOURCE_DIR}")
target_include_directories(libanswer PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include)

target_link_libraries()

target_link_libraries(libanswer PRIVATE CURL::libcurl)
add_executable(answer_app main.cpp)
#为answer可执行目标链接libanswer
#target_link_libraries(answer_app libanswer)

if(BUILD_TESTING)
add_subdirectory(tests)
endif()

其他：
cmake -B build#生成构建目录
cmake --build build #执行构建
./build/answer