Set default value to C array when used as function argument

Question

I have the following function:

void getDefaultMaterial(Uint8 rgb[3]);

The problem is that I want rgb argument to have default value. Like that:

void getDefaultMaterial(Uint8 rgb[3]={255, 255, 255});

Unfortunately, the compiler does not like this? Is there another way?

Answer 1

Note that the parameter is a pointer, not an array.
To the compiler, the prototype is equivalent to

void getDefaultMaterial(Uint8* rgb);

Overloading is one alternative:

void getDefaultMaterial(Uint8 rgb[3]);

void getDefaultMaterial()
{
    Uint8 rgb[3] = { 255, 255, 255 };
    getDefaultMaterial(rgb);
}

Although, if rgb is an "out" parameter, the point of this eludes me.

If it's not an "out" parameter, you can use an actual array with a default value, but you need to pass it by const reference:

void getDefaultMaterial(const Uint8 (&rgb)[3] = {255, 255, 255});

or, as an "out" parameter with "default by overloading":

void getDefaultMaterial(Uint8 (&rgb)[3]);

void getDefaultMaterial()
{
    Uint8 rgb[3] = { 255, 255, 255 };
    getDefaultMaterial(rgb);
}