1 /* $NetBSD: msg_166.c,v 1.3 2021/05/16 11:11:37 rillig Exp $ */ 2 # 3 "msg_166.c" 3 4 // Test for message: precision lost in bit-field assignment [166] 5 6 /* lint1-extra-flags: -hp */ 7 8 struct bit_set { 9 10 /* 11 * C99 6.7.2p5 and 6.7.2.1p9 footnote 104 say that for bit-fields of 12 * underlying type 'int', "it is implementation-defined whether the 13 * specifier 'int' designates the same type as 'signed int' or the 14 * same type as 'unsigned int'". 15 * 16 * https://gcc.gnu.org/onlinedocs/gcc/Structures-unions-enumerations 17 * -and-bit-fields-implementation.html says: "By default it is treated 18 * as 'signed int' but this may be changed by the 19 * '-funsigned-bitfields' option". 20 * 21 * Clang doesn't document implementation-defined behavior, see 22 * https://bugs.llvm.org/show_bug.cgi?id=11272. 23 */ 24 25 int minus_1_to_0: 1; /* expect: 344 */ 26 int minus_8_to_7: 4; /* expect: 344 */ 27 unsigned zero_to_1: 1; 28 unsigned zero_to_15: 4; 29 }; 30 31 void example(void) { 32 struct bit_set bits; 33 34 /* Clang doesn't warn about the 1. */ 35 bits.minus_1_to_0 = -2; /* expect: 166 */ 36 bits.minus_1_to_0 = -1; 37 bits.minus_1_to_0 = 0; 38 bits.minus_1_to_0 = 1; /* expect: 166 */ 39 bits.minus_1_to_0 = 2; /* expect: 166 */ 40 41 bits.minus_8_to_7 = -9; /* expect: 166 */ 42 bits.minus_8_to_7 = -8; 43 bits.minus_8_to_7 = 7; 44 bits.minus_8_to_7 = 8; /* expect: 166 */ 45 46 /* Clang doesn't warn about the -1. */ 47 bits.zero_to_1 = -2; /* expect: 164 */ 48 bits.zero_to_1 = -1; /* expect: 164 */ 49 bits.zero_to_1 = 0; 50 bits.zero_to_1 = 1; 51 bits.zero_to_1 = 2; /* expect: 166 */ 52 53 /* Clang doesn't warn about the -8. */ 54 bits.zero_to_15 = -9; /* expect: 164 */ 55 bits.zero_to_15 = -8; /* expect: 164 */ 56 bits.zero_to_15 = 0; 57 bits.zero_to_15 = 15; 58 bits.zero_to_15 = 16; /* expect: 166 */ 59 } 60