| Norman James | 6a58a27 | 2015-10-07 14:34:16 -0500 | [diff] [blame] | 1 | /* CC0 (Public domain) - see LICENSE file for details */
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| 2 | #ifndef CCAN_CHECK_TYPE_H
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| 3 | #define CCAN_CHECK_TYPE_H
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| 4 | #include "config.h"
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| 5 |
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| 6 | /**
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| 7 | * check_type - issue a warning or build failure if type is not correct.
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| 8 | * @expr: the expression whose type we should check (not evaluated).
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| 9 | * @type: the exact type we expect the expression to be.
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| 10 | *
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| 11 | * This macro is usually used within other macros to try to ensure that a macro
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| 12 | * argument is of the expected type. No type promotion of the expression is
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| 13 | * done: an unsigned int is not the same as an int!
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| 14 | *
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| 15 | * check_type() always evaluates to 0.
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| 16 | *
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| 17 | * If your compiler does not support typeof, then the best we can do is fail
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| 18 | * to compile if the sizes of the types are unequal (a less complete check).
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| 19 | *
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| 20 | * Example:
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| 21 | * // They should always pass a 64-bit value to _set_some_value!
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| 22 | * #define set_some_value(expr) \
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| 23 | * _set_some_value((check_type((expr), uint64_t), (expr)))
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| 24 | */
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| 25 |
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| 26 | /**
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| 27 | * check_types_match - issue a warning or build failure if types are not same.
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| 28 | * @expr1: the first expression (not evaluated).
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| 29 | * @expr2: the second expression (not evaluated).
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| 30 | *
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| 31 | * This macro is usually used within other macros to try to ensure that
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| 32 | * arguments are of identical types. No type promotion of the expressions is
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| 33 | * done: an unsigned int is not the same as an int!
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| 34 | *
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| 35 | * check_types_match() always evaluates to 0.
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| 36 | *
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| 37 | * If your compiler does not support typeof, then the best we can do is fail
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| 38 | * to compile if the sizes of the types are unequal (a less complete check).
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| 39 | *
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| 40 | * Example:
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| 41 | * // Do subtraction to get to enclosing type, but make sure that
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| 42 | * // pointer is of correct type for that member.
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| 43 | * #define container_of(mbr_ptr, encl_type, mbr) \
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| 44 | * (check_types_match((mbr_ptr), &((encl_type *)0)->mbr), \
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| 45 | * ((encl_type *) \
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| 46 | * ((char *)(mbr_ptr) - offsetof(enclosing_type, mbr))))
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| 47 | */
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| 48 | #if HAVE_TYPEOF
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| 49 | #define check_type(expr, type) \
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| 50 | ((typeof(expr) *)0 != (type *)0)
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| 51 |
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| 52 | #define check_types_match(expr1, expr2) \
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| 53 | ((typeof(expr1) *)0 != (typeof(expr2) *)0)
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| 54 | #else
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| 55 | #include <ccan/build_assert/build_assert.h>
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| 56 | /* Without typeof, we can only test the sizes. */
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| 57 | #define check_type(expr, type) \
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| 58 | BUILD_ASSERT_OR_ZERO(sizeof(expr) == sizeof(type))
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| 59 |
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| 60 | #define check_types_match(expr1, expr2) \
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| 61 | BUILD_ASSERT_OR_ZERO(sizeof(expr1) == sizeof(expr2))
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| 62 | #endif /* HAVE_TYPEOF */
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| 63 |
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| 64 | #endif /* CCAN_CHECK_TYPE_H */
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