The explicit copy constructor means that the copy constructor will not be called implicitly, which is what happens in the expression:
CustomString s = CustomString("test");
This expression literally means: create a temporary CustomString
using the constructor that takes a const char*
. Implicitly call the copy constructor of CustomString
to copy from that temporary into s
.
Now, if the code was correct (i.e. if the copy constructor was not explicit), the compiler would avoid the creation of the temporary and elide the copy by constructing s
directly with the string literal. But the compiler must still check that the construction can be done and fails there.
You can call the copy constructor explicitly:
CustomString s( CustomString("test") );
But I would recommend that you avoid the temporary altogether and just create s
with the const char*
:
CustomString s( "test" );
Which is what the compiler would do anyway…