[Python-Dev] _PyImport_LoadDynamicModule questions
Martin v. Loewis
30 May 2002 23:35:08 +0200
Guido van Rossum <email@example.com> writes:
> > However, I still think that people creating --enable-shared
> > installations are misguided: You gain nothing (IMO), and you lose a
> > number of benefits:
> Do you understand why people have always been asking for this? Are
> they all misguided? It really is a FAQ (3.30). Why?
People give various reasons:
- (from #400938): "Using a shared library should have an advantage if
you're running multiple instances of Python (be it standalone
interpreter or embedded applications)."
This is nonsense, of course: the interpreter executable is shared
just as well.
- libraries should be shared (405931). There is often no further
rationale given, but I believe "... because that saves disk space"
is the common implication. Given that /usr/local/bin/python would be
the only application of libpythonxy.so on most installation, this
rationale is questionable.
- it simplifies embedding (with the variant "embedding is not possible
without it"). Some people are simply not aware that a libpython.a is
also installed. In 497102, James Henstridge argues that PyXPCOM
mandates a shared libpython, as does gnome-vfs. He might have a case
here, but I think a special-case shared library that exposes all
Python symbols might be more appropriate.
- on the same topic, the PostgreSQL documentation claims that you
cannot build PL/Python without a shared libpython. They admit that
it might work to use the static library, and that it is just the
fault of their build system to not support this scenario:
- For embedded applications, people also bring up "allows sharing at
run-time" argument). In that case, it is factually true. However,
even without a shared libpython, multiple copies of the same
embedded executable (or shared library) will still share code.
- The Windows port uses a python DLL.
To summarize, it probably does have advantages for people who want to
embed Python in applications that are themselves shared libraries. I
think those advantages are outweighed by the problems people may get
with a shared libpython, and who never want to embed Python.
Just my 0.02EUR,