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What way to choose to fix Warning: ULONG_PTR differs in levels of indirection from void * in AC-generated code? #95417

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arhadthedev opened this issue Jul 29, 2022 · 2 comments · May be fixed by #95446
Open
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What way to choose to fix Warning: ULONG_PTR differs in levels of indirection from void * in AC-generated code? #95417

arhadthedev opened this issue Jul 29, 2022 · 2 comments · May be fixed by #95446
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type-feature A feature request or enhancement

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@arhadthedev
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arhadthedev commented Jul 29, 2022 •
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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

_overlapped_CreateIoCompletionPort_impl(PyObject *module, HANDLE FileHandle,
HANDLE ExistingCompletionPort,
ULONG_PTR CompletionKey,
DWORD NumberOfConcurrentThreads);

cpython/Modules/clinic/overlapped.c.h

Line 40 in 3e7cad3

CompletionKey = PyLong_AsVoidPtr(args[2]);

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 becomes CompletionKey = PyLong_AsUlongPtr(args[2]); or
  • add a public Windows-only PyLong_AsUlongPtr entity and document it so Python integrators and module authors also can work with this volatile WinAPI type

Linked PRs

  1. gh-95417: Quick fix of `ULONG_PTR differs in levels of indirection from void *`
    #95538
    skip news
  2. gh-95417: Apply a proper fix for previously fast-fixed `ULONG_PTR differs in levels of indirection from void *`
    #95518
    awaiting review
@arhadthedev arhadthedev added the type-feature A feature request or enhancement label Jul 29, 2022
@eryksun
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eryksun commented Jul 29, 2022

The C API could support cross-platform PyLong_AsUintptr_t() and PyLong_FromUintptr_t(). The type definitions for ULONG_PTR and uintptr_t are compatible in Windows. For 64-bit, they're both unsigned __int64. For 32-bit, uintptr_t is unsigned int, and ULONG_PTR is unsigned long.

@arhadthedev arhadthedev linked a pull request Jul 29, 2022 that will close this issue
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@bedevere-bot bedevere-bot mentioned this issue Aug 1, 2022
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@arhadthedev
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arhadthedev commented Aug 1, 2022

To fix the warning, two steps are necessary:

@bedevere-bot bedevere-bot mentioned this issue Aug 1, 2022
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zooba pushed a commit that referenced this issue Aug 1, 2022
@arhadthedev
gh-95417: Quick fix for "ULONG_PTR differs in levels of indirection f…
858c9a5 
…rom void *" (GH-95538)
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gh-95417: Add PyLong_FromUintptr_t and PyLong_AsUintptr_t arhadthedev/cpython
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