# V2578. MISRA. An identifier with array type passed as a function argument should not decay to a pointer.

This diagnostic rule is based on the software development guidelines developed by MISRA (Motor Industry Software Reliability Association).

This diagnostic rule is only relevant to C++. If you pass an array to a function by pointer, you will lose the array size. As a result, the function may receive an array with a fewer number of elements as an argument than it is expected. During execution the function may violate array bounds. This will result in undefined behavior.

Pass the array only by reference not to lose data on the array size. If a function needs to handle arrays of different lengths, use a class to encapsulate the array and its size.

Example of code that does not follow the rule:

    void foo(int *ptr);
    void bar(int arr[5])
    void bar(const char chars[30]);

    int main
    {
      int array[5] = { 1, 2, 3 };
      foo(array);
      bar(array);
    }

Acceptable version:

    void bar(int (&arr)[5]);

    int main
    {
      int array[7] = { 1, 2, 3, 4, 5 };
      bar(array);
    }

Another code example that does not follow the rule:

    void bar(const char chars[30]);

    int main()
    {
      bar("something");  //const char[10]
    }

An acceptable version with a class for encapsulation:

    template <typename T>
    class ArrayView
    {
      T *m_ptr;
      size_t m_size;

    public:
      template <size_t N>
      ArrayView(T (&arr)[N]) : m_ptr(arr), m_size(N) {}
      // ....
    };

    void bar(ArrayView<const char> arr);

    int main()
    {
      bar("something");
    }

This diagnostic is classified as:

MISRA-CPP-2008-5.2.12