Can CMake specify the base SDK on Mac OS X?

Question

Does anyone know how to do specify the Mac OS X SDK to build against with CMake? I have searched for cmake mac "base sdk" but this turned up nothing.

I am using CMake to generate Unix makefiles.

Update

On my 10.6 install, I see that /Developer/SDKs has the following:

• MacOSX10.4u.sdk
• MacOSX10.5.sdk
• MacOSX10.6.sdk

Perhaps I can get CMake to pass one of these paths to the compiler somehow?

Also, my 10.7 install only has:

• MacOSX10.6.sdk
• MacOSX10.7.sdk

Does this mean that it can only build for these platforms?

Update 2

Damn, I just realised that actually I'm not using Xcode -- so this may affect some answers. Also, I am now trying with Mac OS X 10.8 developer preview (with some weird results, see my answer).

Answer 1

After trying sakra's valid answer (valid as far as CMake is suposed to behave) unsucessfully, I had a dig around and found that if I specify the --sysroot flag to the compiler, it seems to use the correct SDK!

However, I now see this error when I compile against 10.7 (which I don't see with 10.8):

Undefined symbols for architecture i386:
  "_NXArgv", referenced from:
      execSelfNonDaemonized() in libarch.a(CArchDaemonUnix.o)
      CArchDaemonUnix::daemonize(char const*, int (*)(int, char const**)) in libarch.a(CArchDaemonUnix.o)
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [bin/synergyc] Error 1
make[1]: *** [src/cmd/synergyc/CMakeFiles/synergyc.dir/all] Error 2
make: *** [all] Error 2

Note: CArchDaemonUnix is a class in Synergy (an open source project I'm working on).

Update:

Just tried this on my 10.6 install, and I was getting a linker error when trying to compile for 10.5 -- turns out you also need to specify the MACOSX_DEPLOYMENT_TARGET environment variable!

Anyway, here's what I'm doing when running on Mountain Lion (OSX 10.8) to compile for 10.7:

Command line:

MACOSX_DEPLOYMENT_TARGET=10.7

cmake -G "Unix Makefiles" -DCMAKE_OSX_SYSROOT=/Developer/SDKs/MacOSX10.7.sdk/ -DCMAKE_OSX_DEPLOYMENT_TARGET=10.7 ../..

CMakeLists.txt:

set(CMAKE_CXX_FLAGS "--sysroot ${CMAKE_OSX_SYSROOT} ${CMAKE_CXX_FLAGS}")

I hope this helps someone! :-)

Answer 2

Add the following commands on your CMakeLists.txt

set(CMAKE_OSX_SYSROOT macosx10.10)

set(CMAKE_OSX_DEPLOYMENT_TARGET "10.5")

This should be fine.