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c11_generic_expression.c revision 1.6 
      1 /*	$NetBSD: c11_generic_expression.c,v 1.6 2021/06/28 07:55:05 rillig Exp $	*/
      2 # 3 "c11_generic_expression.c"
      3 
      4 /*
      5  * C99 added support for type-generic macros, but these were limited to the
      6  * header <tgmath.h>.  C11 made this feature generally available.
      7  *
      8  * The generic selection is typically used with macros, but since lint1 works
      9  * on the preprocessed source, the test cases look a bit strange.
     10  *
     11  * C99 6.5.1.1 "Generic selection"
     12  */
     13 
     14 /* lint1-extra-flags: -Ac11 */
     15 
     16 /*
     17  * The type of 'var' is not compatible with any of the types from the
     18  * generic-association.  This is a compile-time error.
     19  */
     20 const char *
     21 classify_type_without_default(double var)
     22 {
     23 	/* expect-2: argument 'var' unused */
     24 
     25 	return _Generic(var,
     26 	    long double: "long double",
     27 	    long long: "long long",
     28 	    unsigned: "unsigned"
     29 	);
     30 	/* expect-1: expects to return value [214] */
     31 }
     32 
     33 /*
     34  * In this case, the 'default' expression is selected.
     35  */
     36 const char *
     37 classify_type_with_default(double var)
     38 {
     39 	/* expect-2: argument 'var' unused */
     40 
     41 	return _Generic(var,
     42 	    long double: "long double",
     43 	    long long: "long long",
     44 	    unsigned: "unsigned",
     45 	    default: "unknown"
     46 	);
     47 }
     48 
     49 /*
     50  * The type of a _Generic expression is the one from the selected association.
     51  */
     52 const char *
     53 classify_char(char c)
     54 {
     55 	/* expect-2: argument 'c' unused */
     56 
     57 	return _Generic(c,
     58 	    char: "yes",
     59 	    default: 0.0
     60 	);
     61 }
     62 
     63 /*
     64  * Before cgram.y 1.238 from 2021-06-27, lint accepted a comma-expression,
     65  * which looked as if _Generic would accept multiple arguments before the
     66  * selection.
     67  */
     68 /* ARGSUSED */
     69 const int *
     70 comma_expression(char first, double second)
     71 {
     72 	return _Generic(first, second,	/* expect: syntax error 'second' */
     73 	    char: "first",
     74 	    double: 2.0
     75 	);
     76 	/* expect+1: without returning value [217] */
     77 }
     78 
     79 /*
     80  * Ensure that assignment-expressions are accepted by the grammar, as
     81  * opposed to comma-expressions.
     82  */
     83 /* ARGSUSED */
     84 int
     85 assignment_expression(int first, int second)
     86 {
     87 	return _Generic(first = second,
     88 	    int: second = first
     89 	);
     90 }
     91