Explicit constructor taking multiple arguments

Question

Does making a constructor having multiple arguments explicit have any (useful) effect?

Example:

class A {
    public:
        explicit A( in         


        

Answer 1

The excellent answers by @StoryTeller and @Sneftel are the main reason. However, IMHO, this makes sense (at least I do it), as part of future proofing later changes to the code. Consider your example:

class A {
    public:
        explicit A( int b, int c ); 
};

This code doesn't directly benefit from explicit.

Some time later, you decide to add a default value for c, so it becomes this:

class A {
    public:
        A( int b, int c=0 ); 
};

When doing this, you're focussing on the c parameter - in retrospect, it should have a default value. You're not necessarily focussing on whether A itself should be implicitly constructed. Unfortunately, this change makes explicit relevant again.

So, in order to convey that a ctor is explicit, it might pay to do so when first writing the method.