Return void type in C and C++

Question

This compiles without any warnings.

Is this legal in C and C++ or does it just work in gcc and clang?

If it is legal, is it some new thing after C99?

Answer 1

This code is allowed in C++ but not allowed in C

From Return statement @ cppreference

In a function returning void, the return statement with expression can be used, if the expression type is void.

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OTOH in C11 specs draft n1570:

Major changes in the second edition included:

return without expression not permitted in function that returns a value (and vice versa)

(return with expression not permitted in function that returns a void)

and 6.8.6.4 return

A return statement with an expression shall not appear in a function whose return type is void. A return statement without an expression shall only appear in a function whose return type is void.

(even if the expression evaluates to void)