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msg_166.c revision 1.2 
      1 /*	$NetBSD: msg_166.c,v 1.2 2021/01/31 13:11:08 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: 34 */
     26 	int minus_8_to_7: 4;		/* expect: 34 */
     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