Stefan Behnel <sco...@users.sourceforge.net> added the comment:
I'm aware that these things happen, that's why I said it. Actually, wouldn't it
rather be *correct* for __file__ to be set to the same file path for all
modules that an extension module creates in its init function? That would
suggest that _Py_ModuleImportContext shouldn't be set to NULL after the first
assignment, but instead stay alive until it gets reset by the dynlib loader. If
the loader gets invoked recursively later on, it will do the right thing by
storing away the old value during the import and restoring it afterwards. So
_Py_ModuleImportContext would always point to the path that contains the init
function that is currently being executed.
Regarding the lock (which, I assume, is simply reentrant), it's being acquired
far up when the import mechanism starts, so the dynlib loader and the init
function call are protected.
Note that this does not apply to the reinit case.
_PyImport_FindExtensionObject() does not acquire the lock itself (which seems
correct), and it can be called directly from imp.init_builtin(), i.e. from user
code. Maybe that's why the _Py_PackageContext protocol was not implemented
there. That's rather unfortunate, though. I guess the reasoning is that new
code that uses this new feature is expected to actually be reentrant, also in
parallel, because the module it creates and works on is local to the current
thread until the init function terminates. So the import lock is not strictly
required here. This does complicate the __file__ feature, though, so the second
("reinit") patch won't work as is. I think the right fix for Python 4 would be
to simply pass a context struct into the module init function.
On a related note, I just stumbled over this code in
_PyImport_FindExtensionObject():
else {
if (def->m_base.m_init == NULL)
return NULL;
mod = def->m_base.m_init();
if (mod == NULL)
return NULL;
PyDict_SetItem(PyImport_GetModuleDict(), name, mod);
Py_DECREF(mod);
}
if (_PyState_AddModule(mod, def) < 0) {
PyDict_DelItem(PyImport_GetModuleDict(), name);
Py_DECREF(mod);
return NULL;
}
If PyDict_SetItem() fails, this is bound to crash. I think it would be worth
looking into this mechanism a bit more.
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<http://bugs.python.org/issue13429>
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