What about unused variables?

[swestin]

The guidelines proscribe declaring unused types, tags on structures or enums, macros, or labels.

Shouldn't there be a prohibition of undeclared variables, too?

-Stephen H. Westin

[misra-c]

We are assuming that the question is intended to read "Shouldn't there be a prohibition of unused variables, too?"

Rule 2.7 covers variables that are declared as parameters to functions.

MISRA C:2012 permits other variables to be initialised and not used. However, if a variable is assigned a value, which is not used, then dead code will exist and rule 2.2 will be violated.

Unused initialisations are permitted because a common programming style is to use configuration files and conditional compilation. This can lead in some configurations to some variables being initialised but never used.

[misra-c]

A new Rule 2.8 "A project should not contain unused object definitions" was added by MISRA C:2012 Amendment 4

Thanks for the suggestion