[stmt.while]
A while statement is equivalent to
[Note 1:
The variable created in the condition is destroyed and created with each iteration of the loop.
[Example 1: struct A { int val; A(int i) : val(i) { } ~A() { } operator bool() { return val != 0; } }; int i = 1; while (A a = i) { // ... i = 0; }
In the while-loop, the constructor and destructor are each called twice, once for the condition that succeeds and once for the condition that fails.
— end example]
— end note]