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msg_309.c revision 1.8 
      1 /*	$NetBSD: msg_309.c,v 1.8 2025/02/24 19:49:00 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 /* lint1-extra-flags: -X 351 */
      7 
      8 typedef unsigned char u8_t;
      9 typedef unsigned int u32_t;
     10 typedef unsigned long long u64_t;
     11 
     12 u8_t u8;
     13 u32_t u32;
     14 u64_t u64;
     15 
     16 
     17 void
     18 test(void)
     19 {
     20 
     21 	/*
     22 	 * Both operands of '&' have the same type, therefore no conversion
     23 	 * is necessary and no bits can get lost.
     24 	 */
     25 	u64 = u64 & 0xffffffff00000000ULL;
     26 
     27 	/*
     28 	 * The constant has type 'unsigned 32-bit'.  The usual arithmetic
     29 	 * conversions of '&' convert this constant to unsigned 64-bit.
     30 	 * The programmer may or may not have intended to sign-extend the
     31 	 * bit mask here.  This situation may occur during migration from a
     32 	 * 32-bit to a 64-bit platform.
     33 	 */
     34 	/* expect+1: warning: extra bits set to 0 in conversion of 'unsigned int' to 'unsigned long long', op '&' [309] */
     35 	u64 = u64 & 0xffff0000;
     36 
     37 	/*
     38 	 * The integer constant is explicitly unsigned.  Even in this case,
     39 	 * the code may have originated on a platform where 'x' had 32 bits
     40 	 * originally, and the intention may have been to clear the lower 16
     41 	 * bits.
     42 	 */
     43 	/* expect+1: warning: extra bits set to 0 in conversion of 'unsigned int' to 'unsigned long long', op '&' [309] */
     44 	u64 = u64 & 0xffff0000U;
     45 
     46 	/*
     47 	 * Even if the expression is written as '& ~', which makes the
     48 	 * intention of clearing the lower 16 bits clear, on a 32-bit
     49 	 * platform the integer constant stays at 32 bits, and when porting
     50 	 * the code to a 64-bit platform, the upper 32 bits are preserved.
     51 	 */
     52 	/* expect+1: warning: extra bits set to 0 in conversion of 'unsigned int' to 'unsigned long long', op '&' [309] */
     53 	u64 = u64 & ~0xffffU;
     54 
     55 	/*
     56 	 * Casting the integer constant to the proper type removes all
     57 	 * ambiguities about the programmer's intention.
     58 	 */
     59 	u64 = u64 & (unsigned long long)~0xffffU;
     60 
     61 	/*
     62 	 * In the remaining cases, the constant does not have its most
     63 	 * significant bit set, therefore there is no ambiguity.
     64 	 */
     65 	u64 = u64 & 0xff00;
     66 	u64 = u64 & 0xf0;
     67 	u64 = u64 & 0xc;
     68 	u64 = u64 & 0x2;
     69 	u64 = u64 & 0x1;
     70 
     71 	u8 = u8 & 0x7f;
     72 	u8 = u8 & 0x80;
     73 	u8 = u8 & -0x80;
     74 	/* expect+1: warning: extra bits set to 0 in conversion of 'unsigned char' to 'int', op '&' [309] */
     75 	u8 = u8 & (u8_t)-0x80;
     76 	/* expect+1: warning: extra bits set to 0 in conversion of 'unsigned char' to 'int', op '&' [309] */
     77 	u8 = u8 & (u8_t)-0x80U;
     78 }
     79