Compiler Warning (level 4) C4564

 

The new home for Visual Studio documentation is Visual Studio 2017 Documentation on docs.microsoft.com.

The latest version of this topic can be found at Compiler Warning (level 4) C4564.

method 'method' of class 'class' defines unsupported default parameter 'parameter'

The compiler detected a method with one or more parameters with default values. The default value(s) for the parameters will be ignored when the method is invoked; explicitly specify values for those parameters. If you do not explicitly specify values for those parameters, the C++ compiler will generate an error.

Given the following .dll created with Visual Basic, which allows default parameters on method arguments:

' C4564.vb  
' compile with: vbc /t:library C4564.vb  
Public class TestClass  
   Public Sub MyMethod (a as Integer, _  
                        Optional c as Integer=1)  
   End Sub  
End class  

And the following C++ sample that uses the .dll created with Visual Basic,

// C4564.cpp  
// compile with: /clr /W4 /WX  
#using <C4564.dll>  
  
int main() {  
   TestClass ^ myx = gcnew TestClass();   // C4564  
   myx->MyMethod(9);  
   // try the following line instead, to avoid an error  
   // myx->MyMethod(9, 1);  
}  

Show: