0540			[C] 2nd and 3rd operands of conditional operator '?' must have compatible types.
	Constraint violations				REFERENCE - ISO:C90-6.3.15 Conditional Operator - Constraints

• Both operands have arithmetic type, or
• Both operands have the same structure or union type, or
• Both operands have void type, or
• Both operands are pointers to qualified or unqualified versions of compatible types, or
• One operand has pointer type and the other is a null pointer constant, or
• One operand is a pointer to an object or incomplete type and the other is a pointer to a qualified or unqualified version of void

/*PRQA S 2211,2213,2216,3198,3199,3203,3205,3210,3227,3408,3447,3617,3625 ++*/

struct ST1 {int a; int b;};

extern struct ST1 stx;
extern struct ST1 sty;
extern int   g;
extern int  *pi;
extern char *pc;

void foo(int n)
{
    int r;
    int *p;

    p = (n > 0) ? pi : g;       /* Message 0540 */
    p = (n > 0) ? pi : pc;      /* Message 0540 */


    r = (n > 0) ? n : g;        /* OK           */
    stx = (n > 0) ? stx : sty;  /* OK           */

}

MISRA C:2012 Rules applicable to message 0540: