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

Nov 19 2018

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