1. 加入系统反射

• CMakeList.txt

cmake_minimum_required(VERSION 3.15)# set the project name and version
project(Tutorial VERSION 1.0)# specify the C++ standard
add_library(tutorial_compiler_flags INTERFACE)
target_compile_features(tutorial_compiler_flags INTERFACE cxx_std_11)# add compiler warning flags just when building this project via
# the BUILD_INTERFACE genex
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 a header file to pass some of the CMake settings
# to the source code
configure_file(TutorialConfig.h.in TutorialConfig.h)# add the MathFunctions library
add_subdirectory(MathFunctions)# add the executable
add_executable(Tutorial tutorial.cxx)target_link_libraries(Tutorial PUBLIC MathFunctions tutorial_compiler_flags)# add the binary tree to the search path for include files
# so that we will find TutorialConfig.h
target_include_directories(Tutorial PUBLIC"${PROJECT_BINARY_DIR}")# add the install targets
install(TARGETS Tutorial DESTINATION bin)
install(FILES "${PROJECT_BINARY_DIR}/TutorialConfig.h"DESTINATION include)# enable testing
include(CTest)# does the application run
add_test(NAME Runs COMMAND Tutorial 25)# does the usage message work?
add_test(NAME Usage COMMAND Tutorial)
set_tests_properties(UsagePROPERTIES PASS_REGULAR_EXPRESSION "Usage:.*number")# define a function to simplify adding tests
function(do_test target arg result)add_test(NAME Comp${arg} COMMAND ${target} ${arg})set_tests_properties(Comp${arg}PROPERTIES PASS_REGULAR_EXPRESSION ${result})
endfunction()
target_include_directories(Tutorial PUBLIC"${PROJECT_BINARY_DIR}")# add the install targets
install(TARGETS Tutorial DESTINATION bin)
install(FILES "${PROJECT_BINARY_DIR}/TutorialConfig.h"DESTINATION include)# enable testing
include(CTest)# does the application run
add_test(NAME Runs COMMAND Tutorial 25)# does the usage message work?
add_test(NAME Usage COMMAND Tutorial)
set_tests_properties(UsagePROPERTIES PASS_REGULAR_EXPRESSION "Usage:.*number")# define a function to simplify adding tests
function(do_test target arg result)add_test(NAME Comp${arg} COMMAND ${target} ${arg})set_tests_properties(Comp${arg}PROPERTIES PASS_REGULAR_EXPRESSION ${result})
endfunction()

• MathFunctions/CMakeLists.txt

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(MathFunctionsINTERFACE ${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 sqrtadd_library(SqrtLibrary STATICmysqrt.cxx)# link SqrtLibrary to tutorial_compiler_flagstarget_link_libraries(SqrtLibrary PUBLIC tutorial_compiler_flags)# TODO 1: Include CheckCXXSourceCompilesinclude(CheckCXXSourceCompiles)# TODO 2: Use check_cxx_source_compiles with simple C++ code to verify# availability of:# * std::log# * std::exp# Store the results in HAVE_LOG and HAVE_EXP respectively.# Hint: Sample C++ code which uses log:# #include <cmath># int main() {#   std::log(1.0);#   return 0;# }check_cxx_source_compiles("#include <cmath>int main() {std::log(1.0);return 0;}" HAVE_LOG)check_cxx_source_compiles("#include <cmath>int main() {std::exp(1.0);return 0;}" HAVE_EXP)# TODO 3: Conditionally on HAVE_LOG and HAVE_EXP, add private compile# definitions "HAVE_LOG" and "HAVE_EXP" to the SqrtLibrary target.# Hint: Use target_compile_definitions()if ( HAVE_LOG AND HAVE_EXP )target_compile_definitions(SqrtLibrary PRIVATE "HAVE_LOG" "HAVE_EXP")else()if ( NOT HAVE_LOG )message( WARNING "DONT HAVE LOG FUNC")endif()if ( NOT HAVE_EXP )message( WARNING "DONT HAVE EXP FUNC")endif()endif()target_link_libraries(MathFunctions PRIVATE SqrtLibrary)
endif()# link MathFunctions to tutorial_compiler_flags
target_link_libraries(MathFunctions PUBLIC tutorial_compiler_flags)# install libs
set(installable_libs MathFunctions tutorial_compiler_flags)
if(TARGET SqrtLibrary)list(APPEND installable_libs SqrtLibrary)
endif()
install(TARGETS ${installable_libs} DESTINATION lib)
# install include headers
install(FILES MathFunctions.h DESTINATION include)

2. 测试代码可行性

check_cxx_source_compiles("#include <cmath>int main() {std::exp(1.0);return 0;}" HAVE_EXP)