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示例

target_compile_options(mylib PRIVATE   -O2) # only internal
target_compile_options(mylib INTERFACE -gl) # only external
target_compile_options(mylib PUBLIC    -g)  # same as PRIVATE + INTERFACE

# multiple targets and flags
target_compile_options(mylib1 mylib2 PRIVATE -Wall -Wextra)

target_compile_options(    mylib PUBLIC -DUSEXX)  # Bad
target_compile_definitions(mylib PUBLIC -DUSEXX)  # OK

add_compile_options(-Wall -Wextra) # for all targets in current directory
add_compile_options(-DUSEXX)       # Bad
add_definitions(-DUSEXX)           # OK

使用cmake生成表达式

In you case you can use:

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target_compile_options(${TARGET} PRIVATE
          $<$<COMPILE_LANGUAGE:CXX>:${BUILD_FLAGS_FOR_CXX}>
          $<$<COMPILE_LANGUAGE:C>:${BUILD_FLAGS_FOR_C}>)

or about compilers:

target_compile_options(${TARGET} PRIVATE
          $<$<CXX_COMPILER_ID:Clang>:${BUILD_FLAGS_FOR_CLANG}>
          $<$<CXX_COMPILER_ID:GNU>:${BUILD_FLAGS_FOR_GCC}>
          $<$<CXX_COMPILER_ID:MSVC>:${BUILD_FLAGS_FOR_VISUAL}>)

It is impossible to reliably use target_compile_options() on MSVC.

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