+- MISRA Discussion Forums (https://forum.misra.org.uk)
+-- Forum: MISRA C (https://forum.misra.org.uk/forumdisplay.php?fid=4)
+--- Forum: MISRA C:2012 and MISRA C:2023 guidelines (https://forum.misra.org.uk/forumdisplay.php?fid=21)
+---- Forum: 7.1 The implementation (https://forum.misra.org.uk/forumdisplay.php?fid=178)
+---- Thread: unused enum constant (/showthread.php?tid=1602)
unused enum constant - kprzygoda - 10-03-2022
I have created enum constant and using it only for assigment to uint8_t or if comparison of uint8_t to this constant, coverity from synopsys configured for MISRA C 2012 is generating rule violation: Type has tag xxxx_enum but that tag is never used. Is there any clear way of get rid of this message?
RE: unused enum constant - misra-c - 23-04-2022
The message "Type has tag xxxx_enum but that tag is never used" would indicate a violation of rule 2.4 which implies that you are using the enumeration constants but are never declaring an object with that type.
MISRA C:2012 divides enumeration constants into two types as described in Appendix D.5. They can be summarised as follows
- Anonymous enum type: This does not have a tag and is not used to define any object.
- Named enum type: This either has a tag, typedef or is directly used to name a constant.
It looks as if you are trying to use an enum constant as an "Anonymous enum type", but have included the tag.
Assignments to uint8_t are only possible for assignments of anonymous enum types. For example:
Code:
enum { A = 1, B = 2, C = 3 };
enum tag { ENUM_A = 1, ENUM_B = 2, ENUM_C = 3 };
uint8_t u8 = ENUM_A; // assignment of essentially enum to essentially unsigned char
// violates rule 10.3
uint8_t u8 = A; // assignment of essentially signed char to essentially unsigned char
// permitted by rule 10.3 exception 1Comparison with uint8_t will violation rules 10.4 in both cases
Code:
u8 > ENUM_A // Balance essentially unsigned char with essentially enum type
// violates rule 10.4
u8 > A // Balance essentially unsigned char with essentially signed char type
// violates rule 10.4