1. 使用表达式生成器产生警告

• CMakeList.txt

cmake_minimum_required(VERSION 3.15)project(Tutorial VERSION 1.0)add_library(tutorial_compiler_flags INTERFACE)
target_compile_features(tutorial_compiler_flags INTERFACE cxx_std_11)set(gcc_like_cxx "$<COMPILE_LANG_AND_ID:CXX,ARMClang,AppleClang,Clang,GNU,LCC>")
set(msvc_cxx "$<COMPILE_LANG_AND_ID:CXX,MSVC>")target_compile_options(tutorial_compiler_flags  INTERFACE "$<${gcc_like_cxx}:$<BUILD_INTERFACE:-Wall;-Wextra;-Wshadow;-Wformat=2;-Wunused>>""$<${msvc_cxx}:$<BUILD_INTERFACE:-W3>>")configure_file(TutorialConfig.h.in TutorialConfig.h)add_subdirectory(MathFunctions)add_executable(Tutorial tutorial.cxx)target_link_libraries(Tutorial PUBLIC MathFunctions tutorial_compiler_flags)target_include_directories(Tutorial PUBLIC
"${PROJECT_BINARY_DIR}"
)

• MathFunctions/CMakeList.txt

# create the MathFunctions library
add_library(MathFunctions MathFunctions.cxx)# state that anybody linking to us needs to include the current source dir
# to find MathFunctions.h, while we don't.
target_include_directories(MathFunctions
INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}
)# should we use our own math functions
option(USE_MYMATH "Use tutorial provided math implementation" ON)
if (USE_MYMATH)
target_compile_definitions(MathFunctions PRIVATE "USE_MYMATH")# library that just does sqrt
add_library(SqrtLibrary STATICmysqrt.cxx
)# link SqrtLibrary to tutorial_compiler_flags
target_link_libraries(SqrtLibrary PUBLIC tutorial_compiler_flags)target_link_libraries(MathFunctions PRIVATE SqrtLibrary)
endif()# link MathFunctions to tutorial_compiler_flags
target_link_libraries(MathFunctions PUBLIC tutorial_compiler_flags)