1 /* $NetBSD: gcc_cast_union.c,v 1.4 2023/07/07 19:45:22 rillig Exp $ */
2 # 3 "gcc_cast_union.c"
3
4 /*
5 * Test the GCC extension for casting to a union type.
6 *
7 * As of GCC 10.3.0, GCC only prints a generic warning without any details:
8 * error: cast to union type from type not present in union
9 * No idea why it neither mentions the union type nor the actual type.
10 *
11 * https://gcc.gnu.org/onlinedocs/gcc/Cast-to-Union.html
12 */
13
14 /* lint1-extra-flags: -e -X 351 */
15
16 union anything {
17 _Bool m_bool;
18 char m_char;
19 signed char m_signed_char;
20 unsigned char m_unsigned_char;
21 short m_short;
22 unsigned short m_unsigned_short;
23 int m_int;
24 unsigned int m_unsigned_int;
25 long m_long;
26 unsigned long m_unsigned_long;
27 long long m_long_long;
28 unsigned long long m_unsigned_long_long;
29 /* skip __int128_t and __uint128_t for now */
30 float m_float;
31 double m_double;
32 long double m_long_double;
33
34 struct m_struct {
35 int member;
36 } m_struct;
37 union m_union {
38 int member;
39 } m_union;
40 enum m_enum1 {
41 E1
42 } m_enum1;
43 enum m_enum2 {
44 E2
45 } m_enum2;
46 const char *m_const_char_pointer;
47 double m_double_array[5];
48 void (*m_function)(void *);
49 void (*m_function_varargs)(void *, ...);
50 float _Complex m_float_complex;
51 double _Complex m_double_complex;
52 long double _Complex m_long_double_complex;
53 };
54
55 enum other_enum {
56 OTHER
57 };
58
59 void
test(void)60 test(void)
61 {
62 union anything any;
63
64 any = (union anything)(_Bool)0;
65 any = (union anything)(char)'\0';
66 any = (union anything)(signed char)'\0';
67 any = (union anything)(unsigned char)'\0';
68 any = (union anything)(short)'\0';
69 any = (union anything)(unsigned short)'\0';
70 any = (union anything)(int)'\0';
71 any = (union anything)(unsigned int)'\0';
72 any = (union anything)(long)'\0';
73 any = (union anything)(unsigned long)'\0';
74 any = (union anything)(long long)'\0';
75 any = (union anything)(unsigned long long)'\0';
76 any = (union anything)0.0F;
77 any = (union anything)0.0;
78 any = (union anything)0.0L;
79 any = (union anything)(struct m_struct){ 0 };
80 any = (union anything)(union m_union){ 0 };
81 any = (union anything)E1;
82 any = (union anything)E2;
83 /* GCC allows enum mismatch even with -Wenum-conversion */
84 /* expect+1: error: type 'enum other_enum' is not a member of 'union anything' [329] */
85 any = (union anything)OTHER;
86 /* expect+1: error: type 'pointer to char' is not a member of 'union anything' [329] */
87 any = (union anything)"char *";
88 any = (union anything)(const char *)"char *";
89 /* expect+1: error: type 'pointer to double' is not a member of 'union anything' [329] */
90 any = (union anything)(double[5]){ 0.0, 1.0, 2.0, 3.0, 4.0 };
91 /* expect+1: error: type 'pointer to double' is not a member of 'union anything' [329] */
92 any = (union anything)(double[4]){ 0.0, 1.0, 2.0, 3.0 };
93 /* expect+1: error: type 'pointer to int' is not a member of 'union anything' [329] */
94 any = (union anything)(int[5]){ 0, 1, 2, 3, 4 };
95 any = (union anything)(float _Complex)0.0F;
96 any = (union anything)(double _Complex)0.0;
97 any = (union anything)(long double _Complex)0.0L;
98
99 any = any;
100 }
101