[Python-Dev] Sharing functions between C extension modules in stdlib

[Alexander Belopolsky]

I have learned a long time ago that it is not enough to simply declare
a function in some header file if you want to define it in one module
and use in another.  You have to use what now is known as PyCapsule -
an array of pointers to C functions wrapped in a Python object.
However, while navigating through the time/datetime maze recently I
have come across timefuncs.h which seems to share
_PyTime_DoubleToTimet between time and datetime modules.

I did not expect this to work, but apparently the build machinery
somehow knows how to place _PyTime_DoubleToTimet code in both time.so
and datetime.so:


$ nm build/lib.macosx-10.4-x86_64-3.2-pydebug/datetime.so | grep
_PyTime_DoubleToTimet
000000000000f4e2 T __PyTime_DoubleToTimet
$ nm build/lib.macosx-10.4-x86_64-3.2-pydebug/time.so | grep
_PyTime_DoubleToTimet
0000000000000996 T __PyTime_DoubleToTimet

I have two questions: 1) how does this happen; and 2) is this intentional?

Thanks.