[issue19960] zlib skipped when building 2.7 on macOS without /usr/include installed

[Ned Deily]

Ned Deily <nad at python.org> added the comment:

Now that Apple, as of 10.14, has removed the option to install system header files into their traditional locations (like /usr/include), thus making every build a build from an SDK, this problem is now more noticeable.  At least, I finally noticed it while fixing the more general problems that setup.py had on all branches (see Issue36231).  This issue is in addition and is specific to 2.7.  As can be seen in Ronald's patch, which I didn't find until after I had written my own, the problem is that, in 2.7's setup.py, add_dir_to_list() does not take the SDK manipulation into account and, in particular, skips adding /usr/include because that directory doen't exist in the root filesystem anymore.  On my systems, besides zlib, the dbm and nis modules were also being skipped. Curiously, some other extension modules with system library dependencies do get built properly, like _sqlite3, because their build step in setup.py explicitly added /usr/include to the SDK search paths.

Anyway, the PR I produced is somewhat more complicated that Ronald's original patch.  It's more careful about what paths it checks for and it also stores the directory name, if found, without the prepended SDK path.  That may be important in other steps in setup.py where it is doing path comparisons.  The SDK will eventually get added again, either explicitly or implicitly by the compiler tool chain.

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priority: normal -> high
title: MacOSX: Building 2.7 without the xcode command line  tools installed -> zlib skipped when building 2.7 on macOS without /usr/include installed

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue19960>
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