So you've installed Python from an official binary installer on python.org's Releases page, you've installed Xcode from the App Store and the Command Line Tools from Xcode, you've installed pip from its setup script. And now, you try to "pip-X.Y install pyobjc" and it fails with a whole slew of obscure error messages.
An easy workaround: Don't
The official binary installer seems like the easy way to do things, but it's not. It's built to work with every version of OS X from 10.6 to 10.9. This means whenever you build a package, it will try to build that package to work with every version of OS X from 10.6 to 10.9. This is very hard to do—especially on a 10.8 or 10.9 machine with Xcode 5.
If you're planning to build applications for binary distribution with, e.g., py2app, and you want them to work on an older version of OS X than you have, then you need to get this working. (Although even then, you might be better off building Python exactly the way you want, instead of using the binary installation.) So far, I haven't been able to get this working with Xcode 5; I've been using an old machine that I don't update.
For almost everyone else, it's unnecessary wasted effort.
Python 2
If you're using Python 2, just stick with Apple's pre-installed 2.7.2. Having multiple 2.7 installations at the same time is already a huge headache, and the added problems with building packages… is it really worth it?
Python 3
While it may seem counter-intuitive, building it yourself makes everything easier, because you end up with a Python installation tailored to your build toolchain, not to the Python Mac build machine's toolchain.
And if you use Homebrew, building it yourself is just "brew install python3". Plus, you get setuptools and pip (that work with your system), and a newer sqlite3, real readline, gdbm, and a few other things you wouldn't have thought of.
When are they going to fix it?
I know that the pythonmac SIG are aware of the problem. In fact, the problem has been around for a long time; it's just that the workarounds they've used since 10.6 no longer work. I have no idea what they're planning to do about it. You might want to watch the pythonmac-sig mailing list for progress, or join in to help.
The problem
There are actually two problems.
gcc is gone
The official Python.org binaries are built with Apple's custom gcc-4.2, as supplied by Xcode 3.2.
Xcode 4 stopped supplying gcc-4.2, but offered a transitional compiler called llvm-gcc-4.2 (because it used a custom gcc-4.2 frontend hooked up to the llvm backend), and the toolchain came with wrappers named things like "gcc-4.2" and "g++-4.2" and so on. This actually had some problems building Python itself, but for building extension modules—even complex ones like numpy and pyobjc—you usually got away with it.
Xcode 5 dropped llvm-gcc-4.2 as well. Now, all you've got is clang. And, while "gcc" is a wrapper around clang, "gcc-4.2" does not exist at all. So, many extensions will just fail to build, because they're looking for a compiler named "gcc-4.2" (or a C++ compiler named "g++-4.2", or a linker frontend named "gcc-4.2", or…). The new compiler—which Apple calls "Apple LLVM 5.0 (clang-500.2.76) (based on LLVM 3.3svn)", just to make it impossible for anyone to refer to—does a much better job than llvm-gcc-4.2; if you can just get distutils to use it everywhere, everything pretty much just works.
In some cases, just passing "CC=clang CXX=clang++" environment variables to the build will work. You can get further by also adding "MAINCC=clang LINKCC=clang". Anything that needs to run a configure script will _still_ end up picking up gcc-4.2, however, and there may be similar issues with projects that first build a local distutils.cfg or similar.
One workaround is to edit /Library/Frameworks/Python.framework/Versions/X.Y/lib/pythonX.Y/config-X.Ym/Makefile to fix all references to gcc and g++ to instead reference clang and clang++, then cross your fingers. This seems to work.
Alternatively, you could create a symlink, or a hardlink, from /usr/bin/gcc to /usr/local/bin/gcc-4.2, and likewise for g++, and cross your fingers even tighter. I haven't tried this.
10.8 is the oldest SDK
We've always been at war with Eastasia, and we've always been compiling for 10.8. There has never been an older SDK. References in your configure scripts to MacOS10.6.sdk are errors.
Many extensions will build just fine without the 10.6 SDK—but they'll quietly build for your native system, which defeats the purpose of building a redistributable application.
You can still find the 10.6 and 10.7 SDKs in older Xcode packages from Apple (and, for 10.7, you can download the latest Command Line Tools for Lion, which is just the SDK slightly repackaged). Then you can copy them into /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/ and… whether they'll actually work, I don't know. They won't have an SDKSettings.plist file. They won't be registered in the list of known SDKs; the GUI and xcodebuild certainly won't find them, but maybe specifying them on the command line will work. Or maybe only if you use absolute paths.
Add a comment