STINNER Victor added the comment:
> The complication is that the return values of spawn*() etc are process
> handles (cast to intptr_t), not pids:
I opened this issue because of a compiler warning in os.waitpid(). On Windows,
the C function _cwait() is used and it expects a intptr_t ("handle to the
process to wait on") and returns a intptr_t ("returns the handle of the
specified process").... But os.waitpid() uses PyLong_FromPid() to convert the C
intptr_t to a Python int, which may loose most significant bits (sizeof(void*)
> sizeof(int) on Windows x64).
I see that PC/pyconfig.h defines "typedef int pid_t;". Because intptr_t is
bigger than int, using intptr_t is compatible with pid_t, at least for
PyLong_FromPid(). It may be a problem in the other direction: PyLong_AsPid().
Python code using Windows HANDLE is not consistent. Sometimes, intptr_t is
used, sometimes long is used. Examples:
- msvcrt.open_osfhandle() parses an handle with "l" (long) format, whereas it
should uses a wider type.
- msvcrt.get_osfhandle() uses PyLong_FromVoidPtr() to convert an C Py_intptr_t
to a Python int, with the following comment:
/* technically 'handle' is not a pointer, but a integer as
large as a pointer, Python's *VoidPtr interface is the
most appropriate here */
--
@sbt: Would you like to have a strict separation between UNIX-like pid (pid_t)
and Windows process identifier (HANDLE)?
Can we consider that HANDLE is a pointer? Or can we consider that HANDLE is
intptr_t or intmax_t? See the issue #17870 which proposes an API to handle
intmax_t.
If we want to be more explicit, we should add functions to handle the C HANDLE
type. Example:
- PyLong_FromHandle(): C HANDLE to Python int
- PyLong_AsHandle(): Python int to C HANDLE
- "P" format (or another letter): PyArg_Parse*() format
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<http://bugs.python.org/issue17931>
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