Is the destructor of a local object inside a loop guaranteed to be called before the next iteration?

Question

When I have a loop and inside this loop create a new stack variable (not allocating it on the heap and variable holding it declared inside the loop body), is the destructor of this object guaranteed to be called before the next iteration starts, or might loop unrolling by the compiler change something about that?

Answer 1

From n4800:

§6.3.3 Block Scope:

A name declared in a block (8.3) is local to that block; it has block scope. Its potential scope begins at its point of declaration (6.3.2) and ends at the end of its block. A variable declared at block scope is a local variable.

§10.3.6 Destructors:

A destructor is invoked implicitly [...] when the block in which an object is created exits (8.7)

§4.1.1 Abstract machine:

This provision is sometimes called the “as-if” rule, because an implementation is free to disregard any requirement of this document as long as the result is as if the requirement had been obeyed, as far as can be determined from the observable behavior of the program.

[Emphasis mine]

So, yes. Your variable goes out of scope at the end of the loop (which is a block) and hence its destructor is called as far as anyone observing the behavior of the program can tell.