Is Stateful Metaprogramming Doomed in C ?

Stateful Metaprogramming: Still Ill-Formed in C

Since its conception, stateful metaprogramming, also known as the "constexpr counter," has been a subject of fascination and debate. This technique allows developers to capture and retrieve metadata within template functions, enabling state storage in metaprogramming.

Concerns and the CWG

The C Working Group (CWG) has recognized concerns regarding stateful metaprogramming. Active Issue 2118 notes that such techniques are arcane and should be made ill-formed. In May 2015, the CWG agreed to prohibit these practices, although the exact mechanism for doing so remains undetermined.

Aftermath and Conclusion

Despite its legality in C 14, the status of stateful metaprogramming remains in limbo. Until a formal prohibition mechanism is established, it may persist as a valid technique. However, it's important to note that the CWG may retroactively rule it as a DR if a suitable mechanism is developed. Therefore, while stateful metaprogramming may currently be feasible, its future in C is uncertain.

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