1 /* $NetBSD: c11_generic_expression.c,v 1.19 2023/08/06 19:44:50 rillig Exp $ */
2 # 3 "c11_generic_expression.c"
3
4 /* lint1-extra-flags: -X 351 */
5
6 /*
7 * C99 added support for type-generic macros, but these were limited to the
8 * header <tgmath.h>. C11 made this feature generally available.
9 *
10 * The generic selection is typically used with macros, but since lint1 works
11 * on the preprocessed source, the test cases look a bit strange.
12 *
13 * C11 6.5.1.1 "Generic selection"
14 */
15
16 /* lint1-extra-flags: -Ac11 */
17
18 /*
19 * The type of 'var' is not compatible with any of the types from the
20 * generic-association. This is a constraint violation that the compiler must
21 * detect, therefore lint doesn't repeat that diagnostic.
22 */
23 const char *
classify_type_without_default(double var)24 classify_type_without_default(double var)
25 {
26 /* expect-2: warning: parameter 'var' unused in function 'classify_type_without_default' [231] */
27
28 return _Generic(var,
29 long double: "long double",
30 long long: "long long",
31 unsigned: "unsigned"
32 );
33 /* expect-1: error: function 'classify_type_without_default' expects to return value [214] */
34 }
35
36 /*
37 * In this case, the 'default' expression is selected.
38 */
39 const char *
classify_type_with_default(double var)40 classify_type_with_default(double var)
41 {
42 /* expect-2: warning: parameter 'var' unused in function 'classify_type_with_default' [231] */
43
44 return _Generic(var,
45 long double: "long double",
46 long long: "long long",
47 unsigned: "unsigned",
48 default: "unknown"
49 );
50 }
51
52 /*
53 * The type of a _Generic expression is the one from the selected association.
54 */
55 const char *
classify_char(char c)56 classify_char(char c)
57 {
58 /* expect-2: warning: parameter 'c' unused in function 'classify_char' [231] */
59
60 return _Generic(c,
61 char: "yes",
62 default: 0.0
63 );
64 }
65
66 /*
67 * Before cgram.y 1.238 from 2021-06-27, lint accepted a comma-expression,
68 * which looked as if _Generic would accept multiple arguments before the
69 * selection.
70 */
71 /* ARGSUSED */
72 const int *
comma_expression(char first,double second)73 comma_expression(char first, double second)
74 {
75 /* expect+1: error: syntax error 'second' [249] */
76 return _Generic(first, second,
77 char: "first",
78 double: 2.0
79 );
80 /* expect+1: warning: function 'comma_expression' falls off bottom without returning value [217] */
81 }
82
83 /*
84 * Ensure that assignment-expressions are accepted by the grammar, as
85 * opposed to comma-expressions.
86 */
87 /* ARGSUSED */
88 int
assignment_expression(int first,int second)89 assignment_expression(int first, int second)
90 {
91 return _Generic(first = second,
92 int: second = first
93 );
94 }
95
96 int
primary_expression(void)97 primary_expression(void)
98 {
99 return _Generic(0, int: assignment_expression)(0, 0);
100 }
101
102 /*
103 * The types don't match, therefore build_generic_selection returns NULL,
104 * which is then silently ignored by init_expr. This situation is already
105 * covered by the compilers, so there is no need for lint to double-check it.
106 */
107 const char *x = _Generic(
108 1ULL + 1.0f,
109 int: 1
110 );
111