When building from source, if I create multiple configuration directories and build from there e.g.:

mkdir configs
cd configs
mkdir config-A
cd config-A
../../configure
make
cd ..
mkdir config-B
cd config-B
../../configure --enable-shared
make
cd ../config-A
./python -c "import sysconfig; print(sysconfig.get_config_var('CONFIG_ARGS')

then sysconfig's settings are the same for *every* config, reflecting those of the last build (config-B above, rathern than those of config-A).

This turns out to be due to this:
   ./python -SE -m sysconfig --generate-posix-vars
This generates $(srcdir)/Lib/_sysconfigdata.py for whichever config was last

Is there a way of fixing this whilst keeping it a python file?  Or do we need to build from a C file, perhaps?

Note to self: workaround is to
  rm ../../Lib/_sysconfigdata.py || make ../../Lib/_sysconfigdata.py
before running my tests in either configuration, to force the file to be regenerated using what "make" thinks the settings are

Would always recreating _sysconfigdata.py solve the problem?

> Is there a way of fixing this whilst keeping it a python file?  Or do
> we need to build from a C file, perhaps?

Well I hope we don't make it a C file just for that reason. It would complicate the generation code quite a bit (right now it's just 3 lines long).

I tend to use separate clones myself (actually, I use "hg share" to avoid multiple pulls).

I'm pretty sure this is a duplicate of http://bugs.python.org/issue15298 (which should be fixed shortly).

Feel free to re-open if I'm wrong.