Re: [Mingw-w64-public] wspiapi.h:50:20: warning: cast between incompatible function types from ‘void (__attribute__((stdcall)) *)(struct addrinfo *)’ to ‘int (__attribute__((stdcall)) *)()’ [-Wcast-function-type]

[LIU Hao]

在 2024-08-05 20:14, Antonin Décimo 写道:

C99 in Annex J.5.7 Function pointer casts states:
1 A pointer to an object or to void may be cast to a pointer to a
function, allowing data to be invoked as a function (6.5.4).
2 A pointer to a function may be cast to a pointer to an object or to
void, allowing a function to be inspected or modified (for example, by
a debugger) (6.5.4)

and MSVC, clang, and GCC implement this extension.

GCC warns about it if `-Wpedantic` is specified:
(https://gcc.godbolt.org/z/e4bh3jcvs)
   ```
   <source>:6:12: warning: ISO C forbids conversion of function pointer
   to object pointer type [-Wpedantic]
       6 |     return (void*) fn;
         |            ^
   ```



Thankfully all Windows targets (maybe all POSIX systems too) have a flat 
address space.





--
Best regards,
LIU Hao

And that's the reason for not doing that. On a system with segmented memory, a pointer to code may assume a different segment from a pointer to data, so even they may appear to hold the same numeric value, they don't point to the same identity.

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