Can C References Have Default Parameter Values?

Default Parameter Values for References in C

When passing parameters by reference, it is typically not possible to provide a default value. However, there is an exception to this rule for constant references.

Consider the following function declaration:

virtual const ULONG Write(ULONG &State = 0, bool sequence = true);

This code will result in an error because C does not allow temporary values (like the default value of 0) to be bound to non-const references.

Solution for Constant References

For constant references, it is possible to provide a default value. This is because the compiler can guarantee that the reference will not be modified.

virtual const ULONG Read(const ULONG &State = 0, bool sequence = true);

Workaround for Non-Constant References

While default values cannot be assigned to non-const references, there is a workaround using a static instance:

static int AVAL = 1;

void f( int &x = AVAL ) {
   // stuff
}

The function f can now be called with or without a parameter, with the default value of AVAL used when no parameter is provided. However, this approach has limited practical use.

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