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msg_309.c revision 1.6 
      1 /*	$NetBSD: msg_309.c,v 1.6 2022/10/15 21:19:15 rillig Exp $	*/
      2 # 3 "msg_309.c"
      3 
      4 // Test for message: extra bits set to 0 in conversion of '%s' to '%s', op '%s' [309]
      5 
      6 int
      7 scale(unsigned long long x) {
      8 
      9 	/*
     10 	 * Both operands of '&' have the same type, therefore no conversion
     11 	 * is necessary and no bits can get lost.
     12 	 */
     13 	if ((x & 0xffffffff00000000ULL) != 0)
     14 		return 32;
     15 
     16 	/*
     17 	 * The constant has type 'unsigned 32-bit'.  The usual arithmetic
     18 	 * conversions of '&' convert this constant to unsigned 64-bit.
     19 	 * The programmer may or may not have intended to sign-extend the
     20 	 * bit mask here.  This situation may occur during migration from a
     21 	 * 32-bit to a 64-bit platform.
     22 	 */
     23 	/* expect+1: warning: extra bits set to 0 in conversion of 'unsigned int' to 'unsigned long long', op '&' [309] */
     24 	if ((x & 0xffff0000) != 0)
     25 		return 16;
     26 
     27 	/*
     28 	 * The integer constant is explicitly unsigned.  Even in this case,
     29 	 * the code may have originated on a platform where 'x' had 32 bits
     30 	 * originally, and the intention may have been to clear the lower 16
     31 	 * bits.
     32 	 */
     33 	/* expect+1: warning: extra bits set to 0 in conversion of 'unsigned int' to 'unsigned long long', op '&' [309] */
     34 	if ((x & 0xffff0000U) != 0)
     35 		return 16;
     36 
     37 	/*
     38 	 * Even if the expression is written as '& ~', which makes the
     39 	 * intention of clearing the lower 16 bits clear, on a 32-bit
     40 	 * platform the integer constant stays at 32 bits, and when porting
     41 	 * the code to a 64-bit platform, the upper 32 bits are preserved.
     42 	 */
     43 	/* expect+1: warning: extra bits set to 0 in conversion of 'unsigned int' to 'unsigned long long', op '&' [309] */
     44 	if ((x & ~0xffffU) != 0)
     45 		return 16;
     46 
     47 	/*
     48 	 * Casting the integer constant to the proper type removes all
     49 	 * ambiguities about the programmer's intention.
     50 	 */
     51 	if ((x & (unsigned long long)~0xffffU) != 0)
     52 		return 16;
     53 
     54 	/*
     55 	 * In the remaining cases, the constant does not have its most
     56 	 * significant bit set, therefore there is no ambiguity.
     57 	 */
     58 	if ((x & 0xff00) != 0)
     59 		return 8;
     60 	if ((x & 0xf0) != 0)
     61 		return 4;
     62 	if ((x & 0xc) != 0)
     63 		return 2;
     64 	if ((x & 0x2) != 0)
     65 		return 1;
     66 	return (int)(x & 0x1);
     67 }
     68