MISRA C:2012 Rule 11.6

A cast shall not be performed between pointer to void and an arithmetic type

Description

Rule Definition

A cast shall not be performed between pointer to void and an arithmetic type¹ .

Rationale

Conversion between integer types and pointers to void can cause errors or undefined behavior.

• If an integer type is cast to a pointer, the resulting pointer can be incorrectly aligned. The incorrect alignment causes undefined behavior.

• If a pointer is cast to an arithmetic type, the resulting value can be outside the allowed range for the type.

Conversion between non-integer arithmetic types and pointers to void is undefined.

Polyspace Implementation

Casts or implicit conversions from NULL or (void*)0 do not generate a warning.

Troubleshooting

If you expect a rule violation but do not see it, refer to Diagnose Why Coding Standard Violations Do Not Appear as Expected.

Examples

Casts Between Pointer to void and Arithmetic Types

void foo(void) {

    void          *p;
    unsigned int  u;
    unsigned short r;

    p = (void *) 0x1234u;            /* Non-compliant - undefined */
    u = (unsigned int) p;            /* Non-compliant - undefined */

    p = (void *) 0;                  /* Compliant - Exception */

}

In this example, p is a pointer to void. The rule is violated when:

• An integer value is cast to p.

• p is cast to an unsigned int type.

The rule is not violated if an integer constant with value 0 is cast to a pointer to void.

Check Information

Group: Pointer Type Conversions

Category: Required

AGC Category: Required

Version History

Introduced in R2014b