cmake if-else- else-endif 条件语句

​​代码在git​​

CMakeLists.txt

# set minimum cmake version
cmake_minimum_required(VERSION 3.5 FATAL_ERROR)

# project name and language
project(recipe-04 LANGUAGES CXX)

# introduce a toggle for using a library
set(USE_LIBRARY OFF)

message(STATUS "Compile sources into a library? ${USE_LIBRARY}")

# BUILD_SHARED_LIBS is a global flag offered by CMake
# to toggle the behavior of add_library
set(BUILD_SHARED_LIBS OFF)

# list sources
list(APPEND _sources Message.hpp Message.cpp)

if(USE_LIBRARY)
  # add_library will create a static library
  # since BUILD_SHARED_LIBS is OFF
  add_library(message ${_sources})

  add_executable(hello-world hello-world.cpp)

  target_link_libraries(hello-world message)
else()
  add_executable(hello-world hello-world.cpp ${_sources})
endif()

set(USE_LIBRARY OFF) 默认直接从源码编译，不使用库文件

CMakeCache.txt  CMakeFiles  cmake_install.cmake  hello-world  Makefile

set(USE_LIBRARY ON) add_library(message ${_sources})　默认是静态库，build 文件夹下有 libmessage.a　静态库文件

CMakeCache.txt  CMakeFiles  cmake_install.cmake  hello-world  libmessage.a  Makefile

set(USE_LIBRARY ON) 　　set(BUILD_SHARED_LIBS OFF)　　编译动态库，build 文件夹下有 libmessage.so　动态库文件

CMakeCache.txt  CMakeFiles  cmake_install.cmake  hello-world  libmessage.so  Makefile