[Python-Dev] Bug in Py_InitModule4

["Martin v. Löwis"]

Collin Winter wrote:
> While working with Subversion's python API bindings this morning, I
> discovered a function in one of their modules illegally named "import"
> (svn.client.import, for the curious). Because the extension module in
> question is written in C, the interpreter doesn't flag the
> otherwise-illegal identifier "import" at compile-time; if you try to
> call the function at runtime, however, the interpreter raises a
> SyntaxError, since svn.client.import is an illegal name.

There is still a way to call the function, though, through

import_ = svn.client.__dict__['import']
import_()

> My question is this: is there any interest in preventing situations
> like this by including checks in Python/modsupport.c:Py_InitModule4 to
> make sure that the PyMethodDef contains only valid identifiers, or is
> this a case of "if it hurts when you do that, don't do that"?

I cannot see a "complete" solution, i.e. one that works for all
types, all methods and attribute names of all types, and so on.
There might not even be a way to determine all identifiers that
some module wants to support, other than by inspecting the source
code.

Also, this is not a frequently-reported problem: if people find they
cannot call a certain method, they just rename the function and
be done. If nobody detects that a function is not callable, then
the function is possible just useless.

If this is a SWIG-generated module, I would see a bug in SWIG here:
SWIG should know what the Python keywords are, and rename all functions
following some pattern (traditionally, suffixing an underscore).

Regards,
Martin