Synopsis

(Required) Subtraction between pointers shall only be applied to pointers that address elements of the same array.

Enabled by default

Yes

Severity/Certainty

High/Medium

Full description

Subtracting pointers of different arrays may lead to undefined behaviour. This check is identical to MISRAC++2023-8.7.2.

Coding standards

Code examples

The following code example fails the check and will give a warning:

#include <cstddef>

void example( int * ptr ) {
  int a1[10];
  int * p1 = &a1[1];

  std::ptrdiff_t diff = ptr - p1; // Non-compliant
}

The following code example passes the check and will not give a warning about this issue:

#include <cstddef>

void example() {
  int a1[10];
  int * p1 = &a1[1];

  std::ptrdiff_t diff = p1 - a1;  // Compliant
}