2 Project MISRA C:2012 Deviations

Required: misra-c2012-19.2  

Justification: This deviation applies to each LIN data frame union defined in the LIN configuration file. LIN data frames consist of one to eight data bytes, packed with varying sizes of signal data bits and bytes. These signal data are arranged to fit in a frame and will be read and written individually in the application. Unions provide the most practical solution for accessing the full data frame and individual signal data.  

The rationale for this rule states: “If a union member is written and then a different union member is read back, the behavior depends on the relative sizes of the members. If this rule is not followed, the kinds of behavior that need to be determined are: Padding, Alignment, Endianness, and Bit-order”. The LIN library ensures that each signal byte and bit field within a frame are defined and arranged properly with careful consideration of the behaviors listed in the standard. Thus, this deviation is suppressed for all LIN data frame unions. There are no consequences associated with this deviation.  

E.g.:

/* cppcheck-suppress misra-c2012-19.2 */
typedef union
{ 
    struct
    {
        unsigned Frame1_BoolSignal : 1;
        unsigned : 3;
        unsigned Frame1_Scalar4Signal : 4;
        unsigned Frame1_Scalar16SignalL : 8;
        unsigned Frame1_Scalar16SignalH : 8;
        l_u8 Frame1_ArraySignal[3];
    };
    l_u8 data[FRAME1_BYTES];
} frame1_t;