macos - what does macosx-version-min imply?

Question

When I pass compiler flag -mmacosx-version-min=10.5, what does it mean? I think it implies the result binary is x86, not ppc, but is it 32 bits or 64 bits? I'm compiling on snow leopard, so default output binary is 64 bits. I'm not passing -universal, it's not 32bit-64bit universal binary, I think.

Answer 1

This option will be used by the various availability macros placed into the headers. This means that you can require a minimum version of OS, even if you have a more recent SDK (i.e. target 10.5 with a 10.6 SDK). Using a 10.6 API while targetting 10.5 will trigger a warning and the API will be linked with a weak_import attribute.

Most Apple's API headers contains availability macros for each class, methods, functions or enumerations in order to declare for each of them:

• The minimum OS supported
• The deprecation
• The unavailability
• ...

The macros look like:

• AVAILABLE_MAC_OS_X_VERSION_10_2_AND_LATER
• AVAILABLE_MAC_OS_X_VERSION_10_2_AND_LATER_BUT_DEPRECATED
• ...

As for the architecture, it only depends on the available architectures in the binaries of the SDK. For example with a 10.5 SDK, you can target four architectures (Intel/32bits, PowerPC/32bits, Intel/64bits, PowerPC 64bits), while with a 10.6 SDK, you can only target three architecture (Intel/32bits, PowerPC/32bits, Intel/64bits).

As you are using Snow Leopard, you can either target i386 (Intel/32bits), ppc (PowerPC/32bits) or x86_64 (Intel/64bits) very simply by passing an architecture option like this:

gcc -arch i386

or like this (for configure-based projects):

CFLAGS="-arch i386" LDFLAGS="-arch i386" ./configure