Training courses

Kernel and Embedded Linux

Bootlin training courses

Embedded Linux, kernel,
Yocto Project, Buildroot, real-time,
graphics, boot time, debugging...

Bootlin logo

Elixir Cross Referencer

Open Menu /tests/usr.bin/xlint/lint1/gcc_cast_union.c 
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
/*	$NetBSD: gcc_cast_union.c,v 1.3 2021/08/03 21:18:24 rillig Exp $	*/
# 3 "gcc_cast_union.c"

/*
 * Test the GCC extension for casting to a union type.
 *
 * As of GCC 10.3.0, GCC only prints a generic warning without any details:
 *	error: cast to union type from type not present in union
 * No idea why it neither mentions the union type nor the actual type.
 *
 * https://gcc.gnu.org/onlinedocs/gcc/Cast-to-Union.html
 */

/* lint1-extra-flags: -e */

union anything {
	_Bool m_bool;
	char m_char;
	signed char m_signed_char;
	unsigned char m_unsigned_char;
	short m_short;
	unsigned short m_unsigned_short;
	int m_int;
	unsigned int m_unsigned_int;
	long m_long;
	unsigned long m_unsigned_long;
	long long m_long_long;
	unsigned long long m_unsigned_long_long;
	/* skip __int128_t and __uint128_t for now */
	float m_float;
	double m_double;
	long double m_long_double;

	struct m_struct {
		int member;
	} m_struct;
	union m_union {
		int member;
	} m_union;
	enum m_enum1 {
		E1
	} m_enum1;
	enum m_enum2 {
		E2
	} m_enum2;
	const char *m_const_char_pointer;
	double m_double_array[5];
	void (*m_function)(void *);
	void (*m_function_varargs)(void *, ...);
	float _Complex m_float_complex;
	double _Complex m_double_complex;
	long double _Complex m_long_double_complex;
};

enum other_enum {
	OTHER
};

void
test(void)
{
	union anything any;

	any = (union anything)(_Bool)0;
	any = (union anything)(char)'\0';
	any = (union anything)(signed char)'\0';
	any = (union anything)(unsigned char)'\0';
	any = (union anything)(short)'\0';
	any = (union anything)(unsigned short)'\0';
	any = (union anything)(int)'\0';
	any = (union anything)(unsigned int)'\0';
	any = (union anything)(long)'\0';
	any = (union anything)(unsigned long)'\0';
	any = (union anything)(long long)'\0';
	any = (union anything)(unsigned long long)'\0';
	any = (union anything)0.0F;
	any = (union anything)0.0;
	any = (union anything)0.0L;
	any = (union anything)(struct m_struct){ 0 };
	any = (union anything)(union m_union){ 0 };
	any = (union anything)E1;
	any = (union anything)E2;
	/* GCC allows enum mismatch even with -Wenum-conversion */
	/* expect+1: error: type 'enum other_enum' is not a member of 'union anything' [329] */
	any = (union anything)OTHER;
	/* expect+1: error: type 'pointer to char' is not a member of 'union anything' [329] */
	any = (union anything)"char *";
	any = (union anything)(const char *)"char *";
	/* expect+1: error: type 'pointer to double' is not a member of 'union anything' [329] */
	any = (union anything)(double[5]){ 0.0, 1.0, 2.0, 3.0, 4.0 };
	/* expect+1: error: type 'pointer to double' is not a member of 'union anything' [329] */
	any = (union anything)(double[4]){ 0.0, 1.0, 2.0, 3.0 };
	/* expect+1: error: type 'pointer to int' is not a member of 'union anything' [329] */
	any = (union anything)(int[5]){ 0, 1, 2, 3, 4 };
	any = (union anything)(float _Complex)0.0F;
	any = (union anything)(double _Complex)0.0;
	any = (union anything)(long double _Complex)0.0L;

	any = any;
}