msg_309.c revision 1.8
1 1.8 rillig /* $NetBSD: msg_309.c,v 1.8 2025/02/24 19:49:00 rillig Exp $ */ 2 1.1 rillig # 3 "msg_309.c" 3 1.1 rillig 4 1.4 rillig // Test for message: extra bits set to 0 in conversion of '%s' to '%s', op '%s' [309] 5 1.1 rillig 6 1.7 rillig /* lint1-extra-flags: -X 351 */ 7 1.7 rillig 8 1.8 rillig typedef unsigned char u8_t; 9 1.8 rillig typedef unsigned int u32_t; 10 1.8 rillig typedef unsigned long long u64_t; 11 1.8 rillig 12 1.8 rillig u8_t u8; 13 1.8 rillig u32_t u32; 14 1.8 rillig u64_t u64; 15 1.8 rillig 16 1.8 rillig 17 1.8 rillig void 18 1.8 rillig test(void) 19 1.8 rillig { 20 1.3 rillig 21 1.3 rillig /* 22 1.3 rillig * Both operands of '&' have the same type, therefore no conversion 23 1.3 rillig * is necessary and no bits can get lost. 24 1.3 rillig */ 25 1.8 rillig u64 = u64 & 0xffffffff00000000ULL; 26 1.3 rillig 27 1.3 rillig /* 28 1.3 rillig * The constant has type 'unsigned 32-bit'. The usual arithmetic 29 1.3 rillig * conversions of '&' convert this constant to unsigned 64-bit. 30 1.3 rillig * The programmer may or may not have intended to sign-extend the 31 1.3 rillig * bit mask here. This situation may occur during migration from a 32 1.3 rillig * 32-bit to a 64-bit platform. 33 1.3 rillig */ 34 1.5 rillig /* expect+1: warning: extra bits set to 0 in conversion of 'unsigned int' to 'unsigned long long', op '&' [309] */ 35 1.8 rillig u64 = u64 & 0xffff0000; 36 1.3 rillig 37 1.3 rillig /* 38 1.6 rillig * The integer constant is explicitly unsigned. Even in this case, 39 1.6 rillig * the code may have originated on a platform where 'x' had 32 bits 40 1.6 rillig * originally, and the intention may have been to clear the lower 16 41 1.6 rillig * bits. 42 1.6 rillig */ 43 1.6 rillig /* expect+1: warning: extra bits set to 0 in conversion of 'unsigned int' to 'unsigned long long', op '&' [309] */ 44 1.8 rillig u64 = u64 & 0xffff0000U; 45 1.6 rillig 46 1.6 rillig /* 47 1.6 rillig * Even if the expression is written as '& ~', which makes the 48 1.6 rillig * intention of clearing the lower 16 bits clear, on a 32-bit 49 1.6 rillig * platform the integer constant stays at 32 bits, and when porting 50 1.6 rillig * the code to a 64-bit platform, the upper 32 bits are preserved. 51 1.6 rillig */ 52 1.6 rillig /* expect+1: warning: extra bits set to 0 in conversion of 'unsigned int' to 'unsigned long long', op '&' [309] */ 53 1.8 rillig u64 = u64 & ~0xffffU; 54 1.6 rillig 55 1.6 rillig /* 56 1.6 rillig * Casting the integer constant to the proper type removes all 57 1.6 rillig * ambiguities about the programmer's intention. 58 1.6 rillig */ 59 1.8 rillig u64 = u64 & (unsigned long long)~0xffffU; 60 1.6 rillig 61 1.6 rillig /* 62 1.3 rillig * In the remaining cases, the constant does not have its most 63 1.3 rillig * significant bit set, therefore there is no ambiguity. 64 1.3 rillig */ 65 1.8 rillig u64 = u64 & 0xff00; 66 1.8 rillig u64 = u64 & 0xf0; 67 1.8 rillig u64 = u64 & 0xc; 68 1.8 rillig u64 = u64 & 0x2; 69 1.8 rillig u64 = u64 & 0x1; 70 1.8 rillig 71 1.8 rillig u8 = u8 & 0x7f; 72 1.8 rillig u8 = u8 & 0x80; 73 1.8 rillig u8 = u8 & -0x80; 74 1.8 rillig /* expect+1: warning: extra bits set to 0 in conversion of 'unsigned char' to 'int', op '&' [309] */ 75 1.8 rillig u8 = u8 & (u8_t)-0x80; 76 1.8 rillig /* expect+1: warning: extra bits set to 0 in conversion of 'unsigned char' to 'int', op '&' [309] */ 77 1.8 rillig u8 = u8 & (u8_t)-0x80U; 78 1.3 rillig } 79
Indexes created Thu Oct 23 22:10:10 GMT 2025