sizeof and C-Style Arrays

When you use sizeof on a C-style array directly, like this:

1int myArray[5];
2std::cout << sizeof(myArray);

It returns the total bytes used by the array, which is the number of elements multiplied by the size of each element.

However, when you pass an array to a function, it decays to a pointer to the first element. So inside the function, sizeof is actually being applied to a pointer, not the original array:

1void myFunction(int arr[]) {
2  std::cout << sizeof(arr);
3}
4
5int main() {
6  int myArray[5];
7  myFunction(myArray);
8}

In this case, sizeof(arr) inside myFunction will return the size of an int* pointer, not the size of the original myArray.

To avoid this issue, you can pass the size of the array as a separate parameter to the function, or use templates to deduce the array size at compile time.