Thread: Passing Arrays to Functions...

Hello All:

I have a question about how something works with respect to passing an array to a function. First a quick code example:

Code:

void cat (int dataA[])
{
	//...
}
void dog (int dataB[3])
{
	//...	 
}

int main () 
{
	int x[10] = {11, 13, 15, 17, 19, 21, 23, 25};
	cat(x);
	dog(x);
	return 0;
}

I'm trying to understand some of the details concerning what the int [] as a function parameter really means and how it relates to a pointer.

1) As a function parameter, what exactly does int dataA[] mean and how does it relate to something like int* dataA? sizeof(dataA) in both cases returns 4. However, if one declares an static local array in a function such as int moo[] = {1, 2, 3}; then sizeof(moo) returns 12. So there must be some difference between int dataA[] and int moo[].

2)With dataA of function cat (and dataB in function dog), it is possible to increment them as in dataA++; or dataB++; ... This would lead me to think that even though the parameters are declared as something that looks like an array declaration, the compiler actually is just treating them like int*... Am I missing something?

3)If you do put a number in the [] of a function parameter array, is it used for anything? Does it have any implications? Doesn't seem to matter when sending a 10 element array to dog. Still compiles and executes with no apparent problems. (BTW - i know this shouldn't be done, but i'm still curious of what's going on).

4) can you suggest some reading material that would specifically address some of these issues? I'm finding a ton of references about "what to do" and "what not to do" (don't put number in [] of function parameters), but not a great deal of "why". Any suggestions would be appreciated.

Thanks
-txcs

in function calls, arrays are promoted to pointers. So char array[] == char *array.

Excellent. Thanks for the help.

One clarification follow-up question, though. It seems from the answers that as far as a function parameter declaration is concerned, there is no difference between void foo(int x[]) and void foo(int*x). Is that reasonable?

thanks,
txcs