xref: /src/tests/usr.bin/xlint/lint1/expr_sizeof.c

/*	$NetBSD: expr_sizeof.c,v 1.9 2023/06/30 09:21:52 rillig Exp $	*/
# 3 "expr_sizeof.c"

/*
 * C99 6.5.3.4 "The sizeof operator"
 * C11 6.5.3.4 "The sizeof operator"
 */

/* lint1-extra-flags: -X 351 */

/*
 * A sizeof expression can either take a type name or an expression.
 */
void sink(unsigned long);

struct {
	int member;
} s, *ps;

/*
 * In a sizeof expression taking a type name, the type name must be enclosed
 * in parentheses.
 */
/* expect+1: error: negative array dimension (-4) [20] */
typedef int sizeof_int[-(int)sizeof(int)];

/*
 * In a sizeof expression taking an expression, the expression may or may not
 * be enclosed in parentheses, like any other expression.
 */
/* expect+1: error: negative array dimension (-4) [20] */
typedef int sizeof_paren_zero[-(int)sizeof(0)];
/* expect+1: error: negative array dimension (-4) [20] */
typedef int sizeof_zero[-(int)sizeof 0];

/*
 * Even though 's' is not a constant expression, 'sizeof s' is.
 */
/* expect+1: error: negative array dimension (-4) [20] */
typedef int sizeof_global_var[-(int)sizeof s];
/* expect+1: error: negative array dimension (-4) [20] */
typedef int sizeof_paren_global_var[-(int)sizeof(s)];

/*
 * Even though 'sizeof(s)' may look like a function call expression, the
 * parentheses around 's' are ordinary parentheses and do not influence the
 * precedence.
 *
 * Therefore, the '.' following the '(s)' takes precedence over the 'sizeof'.
 * Same for the '->' following the '(ps)'.  Same for the '[0]' following the
 * '(arr)'.
 */
/* expect+1: error: negative array dimension (-4) [20] */
typedef int sizeof_paren_global_struct_member[-(int)sizeof(s).member];
/* expect+1: error: negative array dimension (-4) [20] */
typedef int sizeof_paren_global_ptr_struct_member[-(int)sizeof(ps)->member];
int arr[] = { 1, 2, 3 };
/* expect+1: error: negative array dimension (-3) [20] */
typedef int arr_count[-(int)sizeof(arr) / (int)sizeof(arr)[0]];

/* FIXME: 'n' is actually used, for the variable length array. */
/* expect+2: warning: argument 'n' unused in function 'variable_length_array' [231] */
void
variable_length_array(int n)
{
	int local_arr[n + 5];

	/*
	 * Since the array length is not constant, it cannot be used in a
	 * typedef.  Code like this is already rejected by the compiler.  For
	 * simplicity, lint assumes that the array has length 1.
	 */
	/* expect+1: error: negative array dimension (-4) [20] */
	typedef int sizeof_local_arr[-(int)sizeof(local_arr)];
}

void
bit_fields(void)
{
	struct {
		_Bool flag0:1;
		_Bool flag1:1;
		_Bool flag2:1;
	} flags;
	/* expect+1: error: negative array dimension (-1) [20] */
	typedef int sizeof_flags[-(int)sizeof(flags)];

	struct {
		struct {
			_Bool flag0:1;
			_Bool flag1:1;
			_Bool flag2:1;
		};
	} anonymous_flags;
	/* FIXME: sizeof must be 1, not 0. */
	typedef int sizeof_anonymous_flags[-(int)sizeof(anonymous_flags)];

	struct {
		unsigned int bits0:16;
		unsigned int bits1:16;
	} same_storage_unit;
	/* expect+1: error: negative array dimension (-4) [20] */
	typedef int sizeof_same_storage_unit[-(int)sizeof(same_storage_unit)];

	// Detect whether a bit-field can span multiple storage units.
	// If so, the size is 12, if not, the size is 16.
	struct {
		unsigned int bits0:24;
		unsigned int bits1:24;
		unsigned int bits2:24;
		unsigned int bits3:24;
	} cross_storage_unit;
	/* expect+1: error: negative array dimension (-16) [20] */
	typedef int sizeof_cross_storage_unit[-(int)sizeof(cross_storage_unit)];

	/*
	 * The bit-fields in a struct may be merged into the same storage
	 * units, even if their types differ. GCC 10, Clang 15 and lint all
	 * agree in packing the first group of bit-fields and the char into
	 * 4 bytes, even though their underlying types differ.  The second
	 * group of bit-fields gets its own storage unit.
	 */
	struct mixed {
		_Bool flag0:1;
		signed int signed0:1;
		unsigned int unsigned0:1;
		char ch[3];
		_Bool flag1:1;
		signed int signed1:1;
		unsigned int unsigned1:1;
	} mixed;
	/* expect+1: error: negative array dimension (-8) [20] */
	typedef int sizeof_mixed[-(int)sizeof(mixed)];
	/* FIXME: Implement build_offsetof correctly. */
	/* expect+3: error: negative array dimension (-8) [20] */
	typedef int offsetof_mixed_ch[
	    -(int)__builtin_offsetof(struct mixed, ch)
	];
}

/*
 * Ensure that anonymous structs and unions are handled correctly.  They were
 * added in C11, and lint did not properly support them until 2023.
 */
void
anonymous_struct_and_union(void)
{
	struct {
		union {
			unsigned char uc16[16];
			unsigned char uc32[32];
		};
	} su_16_32;
	/* FIXME: Must be 32, not 48. */
	/* expect+1: error: negative array dimension (-48) [20] */
	typedef int sizeof_su_16_32[-(int)sizeof(su_16_32)];

	union {
		struct {
			unsigned char uc16[16];
			unsigned char uc32[32];
		};
	} us_16_32;
	/* expect+1: error: negative array dimension (-48) [20] */
	typedef int sizeof_us_16_32[-(int)sizeof(us_16_32)];
}