A most vexing parse error: constructor with no arguments

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.

Answer 2

This is called the Most Vexing Parse issue. When the parser sees

MyClass myObj(); 

It thinks you are declaring a function called myObj that has no parameters and returns a MyClass.

To get around it, use:

MyClass myObj;