Member fields, order of construction

Question

In C++, when doing something like what you see below, is the order of construction guaranteed?

Logger::Logger()
    : kFilePath_("../logs/runtime.log"), logFile_(kFilePath_)
{
    // ...
}

Answer 1

Yes, the order of construction is always guaranteed. It is not, however, guaranteed to be the same as the order in which the objects appear in the initializer list.

Member variables are constructed in the order in which they are declared in the body of the class. For example:

struct A { };
struct B { };

struct S {
    A a;
    B b;

    S() : b(), a() { }
};

a is constructed first, then b. The order in which member variables appear in the initializer list is irrelevant.