build_assert.h (1228B)
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 */