[Python-Dev] hashlib bug when built on OS X 10.6 for 10.5

[Arnaud Bergeron]

If you build python (at least 2.6.5, but probably other versions as
well) in a universal setup using the following command (or similar)
while the machine currently has 10.6 installed:

./configure --with-universal-archs=<doesn't matter>
--enable-universalsdk=/Developer/SDKs/MacOSX10.5.sdk/

then the hashlib module will be unimportable with the following error:

ImportError: No module named _md5

This is because the openssl detection code in setup.py picks up the
system libssl (in /) which is 0.9.8 and selects not to build the
additional _sha256, and _sh512 modules.  Then, when the builds
proceeds the SDK libssl is used (in /Developer/SDKs/MacOSX10.5.sdk/)
which is version 0.9.7 and the openssl_sha256 and openssl_sha512 raise
ValueError in the _hashlib that is built.

Then the fancy code in hashlib.py detects the ValueError, tries to
import _sha256 and gets an ImportError which is caught by the code set
to catch an ImportError of _hashlib and this codes tries to import
_md5 which also fails and gives the error above.

In summary, the code in setup.py finds the wrong library and this
creates a situation with which hashlib.py is not ready to handle.

If the analysis is not clear on certain points, feel free to ask questions.

Arnaud