[Python-Dev] What does the "m" mean for the Mac OS X include folder?

[Ned Deily]

In article <5AB965C9-7D5F-41B6-A5E9-2B881E92A782 at barrys-emacs.org>,
 Barry Scott <barry at barrys-emacs.org> wrote:
> There is a break with convention for the include folder name:
> 
>  /Library/Frameworks/Python.framework/Versions/3.2/include/python3.2m/
> 
> What does the "m" mean?

The "m" means that the Python was configured and built with pymalloc.

This change was introduced by Issue9807 "deriving configuration 
information for different builds with the same prefix" which is an 
adjunct to PEP 3149 "ABI version tagged .so files".  As described in the 
PEP, the idea is to allow the installation of multiple build variants on 
one system, for instance, a set of debug shared libraries (with flag 
"d") alongside the normal optimized libraries.  This was extended in 
Issue9807 to cover the corresponding Include files.   On current Debian 
installs of python3.2, for instance, one sees:

$ ls -ld /usr/include/python3.2*
lrwxrwxrwx [...] /usr/include/python3.2 -> python3.2mu
drwxr-xr-x [...] /usr/include/python3.2mu

("u" means "wide-unicode".)

For OS X framework builds, the unversioned convenience link is not 
created:

$ cd /Library/Frameworks/Python.framework/Versions/3.2
$ ls -l
lrwxr-xr-x [...] Headers@ -> include/python3.2m
-r-xrwxr-x [...] Python*
drwxrwxr-x [...] Resources/
drwxrwxr-x [...] bin/
drwxrwxr-x [...] include/
drwxrwxr-x [...] lib/
drwxrwxr-x [...] share/
$ ls -ld ./include/python3.2*
drwxrwxr-x [...] ./include/python3.2m/

Perhaps it should.  And the implications of the multiple build variants 
feature for OS X frameworks build have probably not yet been fully 
considered.  However, there are now multiple ways to find the proper 
location of the include files and library files, both in 
platform-independent and framework-specific (note the "Headers" link) 
ways.  And they all seem to produce the correct results.

$ bin/python3.2
>>> import sysconfig
>>> sysconfig.get_path('include')
'/Library/Frameworks/Python.framework/Versions/3.2-release_10.6/include/p
ython3.2m'
^D
$ bin/python3-config --include
-I/Library/Frameworks/Python.framework/Versions/3.2-release_10.6/include/
python3.2m 
-I/Library/Frameworks/Python.framework/Versions/3.2-release_10.6/include/
python3.2m

(So good you get it twice in the same line.)

In some ways, this issue falls into a bit of a black hole.  For other 
Unix-y platforms, the PSF (python.org) does not provide binaries or 
installers so issues like installation locations are to some extent at 
the discretion of the various distributors (Debian, Fedora, et al).  For 
Mac OS X and Windows, the PSF also plays the role of binaries/installer 
distributor so some things specific to those installers may need to be 
documented outside of the standard Python documentation set (or properly 
noted).

Feel free to open an issue if you feel something should be changed (code 
or documentation).

-- 
 Ned Deily,
 nad at acm.org