问题
I would like to write code depending on whether the target architecture is e.g. armv7, armv7s, or arm64.
The reason that I can't use sysctlbyname is that this would give me the underlying architecture at runtime, but when arm64 e.g. simulates armv7, sysctl (seemingly) still reports arm64.
回答1:
clang --target=... -mcpu=... -E - -dM </dev/null will output all the pre-defined preprocessor macros (similar works for gcc, too)
I don't see single macro that provides the answer, but you can probably use some combination of __ARM_ARCH and defined(__ARM_ARCH_*).
回答2:
Although this is not a 100% answer to the question, but may be useful:
When using clang, you can discern between 32 bit arm and 64 bit arm using:
__arm__ which is defined for 32bit arm, and 32bit arm only.
__aarch64__ which is defined for 64bit arm, and 64bit arm only.
回答3:
__ARM_ARCH_ISA_A64 is predefined if it's target is arm64,
__ARM_ARCH_7S__ for armv7s,
__ARM_ARCH_7A__ for armv7.
Use: clang -arch arm64 -E -dM - < /dev/null which can output preprocess macro.
来源：https://stackoverflow.com/questions/23934862/what-predefined-macro-can-i-use-to-detect-the-target-architecture-in-clang