Here are a few title options, focusing on the question of safety and portability: * **Is Using Static Member Function Pointers for C API Callbacks Safe and Portable in C ?** (Direct and straightforw

Using Static Member Function Pointers for C API Callbacks in C

In C , the question arises whether using static member function pointers for C API callbacks is a safe and portable approach. The portability is under scrutiny, particularly regarding the Binary Interface (ABI) compatibility.

ABI of Static Member Functions

The ABI of a static member function is typically not identical to that of a C function. Static member functions carry an implicit "this" pointer, which is not present in C functions. This difference can lead to incompatibilities when attempting to pass a static member function pointer directly to a C API that expects a C function pointer.

Standard Compliance

According to the C standard, it is unsafe to use static member function pointers for C API callbacks. As stated in the quoted post from Stack Overflow, the correct approach is to use an "extern 'C'" wrapper function that hides the static member function implementation.

Real-World Issues

Beyond the standard concerns, practical issues have been observed on certain platforms when using static member function pointers in C API callbacks. These issues can manifest as unexpected behavior or crashes.

Conclusion

To ensure portability and avoid potential runtime errors, avoid using static member function pointers directly for C API callbacks. Instead, use an "extern 'C'" wrapper function to provide a C-compatible interface. By adhering to this practice, you can maintain the integrity and functionality of your C code when interacting with C APIs.

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