| Norman James | 6a58a27 | 2015-10-07 14:34:16 -0500 | [diff] [blame] | 1 | /* CC0 (Public domain) - see LICENSE file for details */
|
| 2 | #ifndef CCAN_BUILD_ASSERT_H
|
| 3 | #define CCAN_BUILD_ASSERT_H
|
| 4 |
|
| 5 | /**
|
| 6 | * BUILD_ASSERT - assert a build-time dependency.
|
| 7 | * @cond: the compile-time condition which must be true.
|
| 8 | *
|
| 9 | * Your compile will fail if the condition isn't true, or can't be evaluated
|
| 10 | * by the compiler. This can only be used within a function.
|
| 11 | *
|
| 12 | * Example:
|
| 13 | * #include <stddef.h>
|
| 14 | * ...
|
| 15 | * static char *foo_to_char(struct foo *foo)
|
| 16 | * {
|
| 17 | * // This code needs string to be at start of foo.
|
| 18 | * BUILD_ASSERT(offsetof(struct foo, string) == 0);
|
| 19 | * return (char *)foo;
|
| 20 | * }
|
| 21 | */
|
| 22 | #define BUILD_ASSERT(cond) \
|
| 23 | do { (void) sizeof(char [1 - 2*!(cond)]); } while(0)
|
| 24 |
|
| 25 | /**
|
| 26 | * BUILD_ASSERT_OR_ZERO - assert a build-time dependency, as an expression.
|
| 27 | * @cond: the compile-time condition which must be true.
|
| 28 | *
|
| 29 | * Your compile will fail if the condition isn't true, or can't be evaluated
|
| 30 | * by the compiler. This can be used in an expression: its value is "0".
|
| 31 | *
|
| 32 | * Example:
|
| 33 | * #define foo_to_char(foo) \
|
| 34 | * ((char *)(foo) \
|
| 35 | * + BUILD_ASSERT_OR_ZERO(offsetof(struct foo, string) == 0))
|
| 36 | */
|
| 37 | #define BUILD_ASSERT_OR_ZERO(cond) \
|
| 38 | (sizeof(char [1 - 2*!(cond)]) - 1)
|
| 39 |
|
| 40 | #endif /* CCAN_BUILD_ASSERT_H */
|