Home | History | Annotate | Line # | Download | only in lint1
msg_324.c revision 1.5 
      1 /*	$NetBSD: msg_324.c,v 1.5 2021/01/31 11:12:07 rillig Exp $	*/
      2 # 3 "msg_324.c"
      3 
      4 // Test for message: suggest cast from '%s' to '%s' on op %s to avoid overflow [324]
      5 
      6 /*
      7  * This warning applies to binary operators if the result of the operator
      8  * is converted to a type that is bigger than the operands' result type
      9  * after the usual arithmetic promotions.
     10  *
     11  * In such a case, the operator's result would be truncated to the operator's
     12  * result type (invoking undefined behavior for signed integers), and that
     13  * truncated value would then be converted.  At that point, a few bits may
     14  * have been lost.
     15  */
     16 
     17 /* lint1-flags: -g -S -w -P */
     18 
     19 void
     20 example(char c, int i, unsigned u)
     21 {
     22 	long long ll;
     23 	unsigned long long ull;
     24 
     25 	ll = c + i;		/* expect: 324 */
     26 	ll = i - c;		/* expect: 324 */
     27 	ull = c * u;		/* expect: 324 */
     28 	ull = u + c;		/* expect: 324 */
     29 	ull = i - u;		/* expect: 324 */
     30 	ull = u * i;		/* expect: 324 */
     31 	ll = i << c;		/* expect: 324 */
     32 
     33 	/*
     34 	 * The operators SHR, DIV and MOD cannot produce an overflow,
     35 	 * therefore no warning is necessary for them.
     36 	 */
     37 	ll = i >> c;
     38 	ull = u / c;
     39 	ull = u % c;
     40 
     41 	/*
     42 	 * Assigning the result of an increment or decrement operator to a
     43 	 * differently-sized type is no unusual that there is no need to warn
     44 	 * about it.  It's also more unlikely that there is an actual loss
     45 	 * since this only happens for a single value of the old type, unlike
     46 	 * "ull = u * u", which has many more possibilities for overflowing.
     47 	 */
     48 	ull = u++;
     49 	ull = ++u;
     50 	ull = u--;
     51 	ull = --u;
     52 }
     53