# V2503. MISRA. Implicitly specified enumeration constants should be unique – consider specifying non-unique constants explicitly.

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

This diagnostic rule is relevant only to C-programs. The analyzer has detected a non-unique value among implicitly initialized enumeration elements, which leads to creation of duplicate constant values.

Here is an example of incorrect code:

    enum Suits
    {
      SUITS_SPADES = 1,
      SUITS_CLUBS,
      SUITS_DIAMONDS,
      SUITS_HEARTS,
      SUITS_UNKNOWN = 4
    };

The way the constants are initialized here results in assigning the same values to the elements 'SUITS_HEARTS' and 'SUITS_UNKNOWN'. It is not clear if this was done on purpose or by mistake.

To avoid errors like that, make sure you explicitly initialize all enumeration elements that have non-unique values:

    enum Suits
    {
      SUITS_SPADES = 1,
      SUITS_CLUBS,
      SUITS_DIAMONDS,
      SUITS_HEARTS = 4,
      SUITS_UNKNOWN = 4
    };

This diagnostic is classified as:

MISRA-C-2012-8.12 MISRA-C-2023-8.12