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Static Member Function Pointers as C API Callbacks: A Risky Endeavor
The use of static member function pointers as callbacks for C APIs may appear tempting, but it's a hazardous practice that undermines the C standard.
Reasoning
The C language established regulations in section 3.5 to ensure uniformity in types across declarations, particularly for functions and objects. However, it allows deviations in array types related to major array bounds.
Additionally, in section 7.5, the standard emphasizes that functions with different language linkages (such as C versus C ) are inherently distinct types, even if they are otherwise identical.
Consequences
Trying to use static member function pointers as C API callbacks can result in unpredictable and platform-specific problems. There's a potential for mismatched function prototypes and calling conventions, leading to undefined behavior or exceptions.
Recommended Approach
To maintain safety and portability, it's crucial to adhere to the standard's stipulations and declare C API callbacks as extern "C." This ensures that the callback target aligns with the C language bindings used by the caller.
Conclusion
While the temptation to use static member function pointers as C API callbacks may exist, it's an unsafe and non-portable practice. Developers must prioritize adherence to the C standard and declare callbacks as extern "C" to avoid unexpected issues in their code.
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