c/c++ :: conversion constructor

i didnot know that

a constructor with only one argument acts like a conversion function.
i mean

class A{
A(int);
}

A a=_int_; is valid, and the conversion constructor is called
DOUBT : in this case, the constructor is called many times if i issue some thing like, A a=_int_; a=_int_; . Isnt something fishy here.