determine size of array if passed to function

If it's within your control, use a STL container such as a vector or deque instead of an array.

The other answers overlook one feature of c++. You can pass arrays by reference, and use templates:

template <typename T, int N>
void func(T (&a) [N]) {
    for (int i = 0; i < N; ++i) a[i] = T(); // reset all elements
}

then you can do this:

int x[10];
func(x);

but note, this only works for arrays, not pointers.

However, as other answers have noted, using std::vector is a better choice.

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