In a virtualenv created with virtualenv 1.7.2, using 'virtualenv --distribute -p /usr/local/bin/python PYOBJC-10-6' The /usr/local/bin/python is 2.7.3 built from homebrew several months ago, so it doesn't have MACOSX_DEPLOYMENT_TARGET set as the current tip recipe does. (In case that's useful)
This is on 10.6. The same thing works fine for me on 10.7.
The output below is from easy_install, but I get the same compiler error when using pip.
/Users/mmccrack/Documents/Canonical/source/PYOBJC-10-6 % easy_install pyobjc-core Searching for pyobjc-core Reading http://pypi.python.org/simple/pyobjc-core/ Reading http://pyobjc.sourceforge.net/ Reading http://pyobjc.sourceforge.net/software/index.php Best match: pyobjc-core 2.4 Downloading http://pypi.python.org/packages/source/p/pyobjc-core/pyobjc-core-2.4.tar.gz#md5=267c6b72eb039925222565f4b70f472f Processing pyobjc-core-2.4.tar.gz Writing /var/folders/Nm/NmOdGO0NFGaUkjq70swp+k+++TI/-Tmp-/easy_install-HvhFGY/pyobjc-core-2.4/setup.cfg Running pyobjc-core-2.4/setup.py -q bdist_egg --dist-dir /var/folders/Nm/NmOdGO0NFGaUkjq70swp+k+++TI/-Tmp-/easy_install-HvhFGY/pyobjc-core-2.4/egg-dist-tmp-Tv5pT9 warning: no directories found matching 'Scripts' warning: no directories found matching 'setup-lib' warning: no directories found matching 'source-deps' warning: no previously-included files matching '.DS_Store' found anywhere in distribution warning: no previously-included files matching '*.pyc' found anywhere in distribution warning: no previously-included files matching '*.so' found anywhere in distribution Modules/objc/alloc_hack.m: In function ‘call_NSObject_alloc’: Modules/objc/alloc_hack.m:33: error: Mac OS X version 10.5 or later is needed for zerocost-exceptions error: Setup script exited with error: command '/usr/bin/gcc-4.2' failed with exit status 1