Promela Reference -- pc_value(5)

### `Promela` | ### `Predefined` | ### `pc_value(5)`

`NAME`
`pc_value` - a predefined unary operator for use in `never` claims.

`SYNTAX`
`pc_value(` any_expr `)`

`DESCRIPTION`
The expression `pc_value(pid)` is a predefined function that returns the current control state (an integer) of the process with instantiation number `pid .` The correspondence between the state numbers reported by `pc_value` and statements or line numbers in the Promela source can be checked with runtime option -d on the verifiers generated by Spin. The use of this operator is restricted to `never` claims.

`EXAMPLES`

    never {
            do
            :: pc_value(1) <= pc_value(2)
            && pc_value(2) <= pc_value(3)
            && pc_value(3) <= pc_value(4)
            && pc_value(4) <= pc_value(5)
            od
    }

The claim above is a flawed attempt to enforce a symmetry reduction among five processes. This particular attempt is flawed in that it does not necessarily preserve the correctness properties of the system being verified.

`SEE ALSO`
`never(2)`.

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