# V2563. MISRA. Array indexing should be the only form of pointer arithmetic and it should be applied only to objects defined as an array type.

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

This diagnostic rule applies only to code written in C++. This MISRA rule advises against the use of address arithmetic. The only form of address arithmetic it allows is the subscript operation ('[]') applied to an entity declared as an array.

Exception: the rule allows the use of the increment and decrement operations ('++' and '--').

The use of address arithmetic makes the program less readable and may cause the maintainer to misinterpret the code. The use of indexing, on the contrary, is explicit and makes the code clearer; even if an expression using the subscript operator to index an array contains a mistake, it will be much easier to find. The same is true for increment/decrement operations: they explicitly convey the developer's intention to successively loop over a memory block that makes a continuous data region.

Example of non-compliant code:

    int arr[] = { 0, 1, 2 };
    int *p = arr + 1;        //+V2563
    p += 1;                  //+V2563
    int *q = p[1];           //+V2563

Fixed code:

    int arr[] = { 0, 1, 2 };
    int *p = &arr[1];
    ++p;

This diagnostic is classified as:

MISRA-CPP-2008-5.0.15