Question

I was compiling a C++ program in Cygwin using g++ and I had a class whose constructor had no arguments. I had the lines:

MyClass myObj();
myObj.function1();

And when trying to compile it, I got the message:

error: request for member ‘function1’ in ‘myObj’, which is of non-class type ‘MyClass ()()’

After a little research, I found that the fix was to change that first line to

MyClass myObj;

I could swear I’ve done empty constructor declarations with parentheses in C++ before. Is this probably a limitation of the compiler I’m using or does the language standard really say don’t use parentheses for a constructor without arguments?

Answer 1

Although MyClass myObj(); could be parsed as an object definition with an empty initializer or a function declaration the language standard specifies that the ambiguity is always resolved in favour of the function declaration. An empty parentheses initializer is allowed in other contexts e.g. in a new expression or constructing a value-initialized temporary.