Call a function before function exits

Question

I will begin with an example. Suppose I need to guard a code with a function inside a mutex. There are two ways of implementing this.

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Answer 1

There is a proposal for a generic scope guard to be included in the next C++ standard, and I think it is accepted. You can find an implementation here, together with a link to the reference paper.

In principle, it is similar to the classical ScopeGuard, but it also provides some special cases e.g. for C-like file APIs.