Strange use of passed parameter in C function - NRF905 related

Projects Programming
1

In looking over the code for the NRF905 radio module (Nick Gammon library) I have come across the following:

void nRF905_irq_on(uint8_t origVal)
{
#if NRF905_INTERRUPTS != 0

#ifdef ARDUINO
((void)(origVal));
if(isrState_local > 0)
isrState_local--;
if(isrState_local == 0)
{
attachInterrupt(digitalPinToInterrupt(NRF905_DR), nRF905_SERVICE_DR, RISING);
#if NRF905_INTERRUPTS_AM
attachInterrupt(digitalPinToInterrupt(NRF905_AM), nRF905_SERVICE_AM, CHANGE);
#endif
}
#else
if(origVal)
{
NRF905_REG_EXTERNAL_INT_DR |= _BV(NRF905_BIT_EXTERNAL_INT_DR);
#if NRF905_INTERRUPTS_AM
NRF905_REG_EXTERNAL_INT_AM |= _BV(NRF905_BIT_EXTERNAL_INT_AM);
#endif
}
#endif

#else
((void)(origVal));
#endif
}

Now if one processes the #ifdef for Arduino and assuming NRF905_INTERRUPTS_AM is set and using interrupts (NRF905_INTERRUPTS is set) we get the following:

void nRF905_irq_on(uint8_t origVal)
{
** ((void)(origVal));**
if(isrState_local > 0)
isrState_local--;
if(isrState_local == 0)
{
attachInterrupt(digitalPinToInterrupt(NRF905_DR), nRF905_SERVICE_DR, RISING);
attachInterrupt(digitalPinToInterrupt(NRF905_AM), nRF905_SERVICE_AM, CHANGE);
}
}

The question is what is going on with this line:

((void) (origVal));

origVal is an unsigned 8 bit quantity and is a passed parameter but it is being executed it looks like.

When nrf905_irq_on is called later on in the code we have the following:

** nRF905_irq_on(1);**

So the passed parameter will be a 1 and the line bolded will become:

((void) 1);

I cannot fathom what this does. Can anyone help ???
It seems really bizarre.

2

((void)(origVal)); is there to suppress compiler's warning for unused variable which is "origVal".

3

What I can't fathom is somebody posting 15 times to the forum and still not using code tags for their code. It seems really bizarre.

As for the code, it is a way of "using" the variable so the compiler does not complain about an unused parameter.

4 
What I can't fathom is somebody posting 15 times to the forum and still not using code tags for their code. It seems really bizarre.

The non use of the code tags was by design. I wanted to keep the flow of the query and having little boxes that have their own scroll bar didn't seem conducive to keeping the "flow" in the question. I see them as being of great use when the code is long - which this was not.

On that basis I use features for what they provide and the use in a particular context. The fact that it is code and there is a code tag only indicates a starting point for its use, not its final use.

Anyway the answer was much appreciated blh64 as it has answered a question that has been bugging me about C.

5

Fair enough. But, code tags provide additional benefits in that they don't turn valid code into smiley faces and other such oddities. With code tags, you get exactly what you post, without any translation.