Repository navigation
What way to choose to fix Warning: ULONG_PTR differs in levels of indirection from void * in AC-generated code? #95417
Description
Currently, Argument Clinic generates initialization of ULONG_PTR arguments using PyLong_AsVoidPtr(). The reason is sizeof(ULONG_PTR) == sizeof(void*) akin to C99 uintptr_t.
However, a compiler warns that implicit conversion of a pointer to a pointer-sized integer is not the best practice. This is relevant for _overlapped.CreateIoCompletionPort():
cpython/Modules/clinic/overlapped.c.h
Lines 15 to 18 in 3e7cad3
cpython/Modules/clinic/overlapped.c.h
Line 40 in 3e7cad3
I see three ways to fix it in ULONG_PTR Argument Clinic converter and need an opinion on how to address the warning best:
- generate in-place cast:
CompletionKey = (ULONG_PTR)PyLong_AsVoidPtr(args[2]);or - add a private Windows-only
#define _PyLong_AsUlongPtr(arg) (ULONG_PTR)PyLong_AsVoidPtr(arg)macro so the generated line becomesCompletionKey = PyLong_AsUlongPtr(args[2]);or - add a public Windows-only
PyLong_AsUlongPtrentity and document it so Python integrators and module authors also can work with this volatile WinAPI type
Activity
eryksun commentedon Jul 29, 2022
The C API could support cross-platform
PyLong_AsUintptr_t()andPyLong_FromUintptr_t(). The type definitions forULONG_PTRanduintptr_tare compatible in Windows. For 64-bit, they're bothunsigned __int64. For 32-bit,uintptr_tisunsigned int, andULONG_PTRisunsigned long.arhadthedev commentedon Aug 1, 2022
To fix the warning, two steps are necessary:
PyLong_FromUintptr_tandPyLong_AsUintptr_t#95446 (deciding first whetherPyLong_*Uintptr_tshould be a macro/inline function or exported from python3.dll/.so)ULONG_PTR differs in levels of indirection from void *#95518gh-95417: Quick fix for "ULONG_PTR differs in levels of indirection f…
arhadthedev commentedon Feb 5, 2023
According to https://devguide.python.org/developer-workflow/c-api/#guidelines-for-adding-to-the-limited-api, addition of stable ABI requires long discussion. I'm not ready for this for the sake of a single use case so closing this issue.