[previous] 0544 [next] [U] The value of an incomplete 'union' may not be used.
Explicitly undefined REFERENCE - ISO:C90-6.2.2.1 lvalues

An attempt has been made to use the value of a union of incomplete type. This is not allowed and the result will be undefined.

It is sometimes useful to define a pointer to an incomplete union type. But any attempt to dereference such a pointer will generate message 0544.

For example: 


/*PRQA S 506,2017,3408,3447,3617 ++*/

extern union UN *pun1;          /* Message 3313 */
extern union UN *pun2;

extern void foo(void)
{
    *pun1 = *pun2;              /* Message 0544 */

    pun1 = pun2;                /* OK           */
}

MISRA-C:2004 Rules applicable to message 0544:

Rule  1.2  (Required) No reliance shall be placed on undefined or unspecified behaviour.
Rule  18.1  (Required) All structure and union types shall be complete at the end of a translation unit.

See also:

QA·C Source Code Analyser 8.1
MISRA-C:2004 Compliance Module 3.2
© 2012 Programming Research.
www.programmingresearch.com 		Personality Groups | Glossary | Message Index | MISRA-C:2004 Rule Index Contents