AaronBallman wrote:
> This warning creates issues under Windows, where reinterpret-casting from
> FARPROC to the actual function type is common.
>
> #92738
> [boostorg/interprocess#259](https://github.com/boostorg/interprocess/issues/259)
>
> Reinterpret-casting a function pointer to another function pointer type, then
> back to the original, is well defined in C++. In contrast, using `void*` for
> the same purpose is not.
I think the diagnostic is working as expected in this case -- we cannot tell
that the user is doing a round-trip cast, we can only see there's a single cast
between incompatible function pointer types.
```
warning: cast from 'FARPROC' (aka 'int (*)() __attribute__((stdcall))') to
'GetSystemTimeAsFileTimePtr' (aka 'void (*)(_FILETIME *)
__attribute__((stdcall))')
converts to incompatible function type [-Wcast-function-type-mismatch]
```
or
```
2025-03-12T16:47:36.5368174Z
.\boost/interprocess/detail/win32_api.hpp(1122,59): error: cast from
'farproc_t' (aka 'int (*)() __attribute__((stdcall))') to
'NtQuerySystemInformation_t' (aka 'long (*)(int, void *, unsigned long,
unsigned long *) __attribute__((stdcall))') converts to incompatible function
type [-Werror,-Wcast-function-type-mismatch]
2025-03-12T16:47:36.5371616Z 1122 | NtQuerySystemInformation_t
pNtQuerySystemInformation = reinterpret_cast<NtQuerySystemInformation_t>
2025-03-12T16:47:36.5373049Z |
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2025-03-12T16:47:36.5373933Z 1123 |
(dll_func::get(dll_func::NtQuerySystemInformation));
```
is exactly what this is intended to diagnose. Did you have a change in mind
you'd like to see?
https://github.com/llvm/llvm-project/pull/86131
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