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 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