class test
{
public:
test(int x)
{
val = x;
}
private:
int val;
};
test t(3);
I got 2 points about this code.
test t(3)would call default constructor first, then do val = 3
if there is at least a user-defined constructor, then the compiler does not generate an implicit default constructor
is there a contradiction?
test t(3);
is calling your parametrized constructor( with argument as 3 ) not default constructor. And yes if you define a single constructor with parameter then compiler won't generate dfault constructor.
test t(3)would call default constructor first, then doval = 3
No default constructor is called. val is default-initialised before the test constructor body; if val were a type with a default constructor, then that constructor would be called. But int doesn't have a constructor, and default-initialising just leaves it in its uninitialised state with an indeterminate value.
Perhaps you were thinking that this might call the default constructor of test. It doesn't; no constructor of test would do that, unless you explicitly delegated to that constructor.
if there is at least a user-defined constructor, then the compiler does not generate an implicit default constructor
That's correct, declaring any constructor prevents the implicit default constructor.
is there a contradiction?
No. test doesn't have a default constructor, but nothing here tries to use such a thing.
No, custom constructor doesn't call parameterless constructor, so it is not contradiction.
You're probably mixing two things together - every constructor calls a base class constructor (either default, or some else if you specify the arguments).
