/* CC0 (Public domain) - see ccan/licenses/CC0 file for details */ #ifndef CCAN_BUILD_ASSERT_H #define CCAN_BUILD_ASSERT_H /** * BUILD_ASSERT - assert a build-time dependency. * @cond: the compile-time condition which must be true. * * Your compile will fail if the condition isn't true, or can't be evaluated * by the compiler. This can only be used within a function. * * Example: * #include <stddef.h> * ... * static char *foo_to_char(struct foo *foo) * { * // This code needs string to be at start of foo. * BUILD_ASSERT(offsetof(struct foo, string) == 0); * return (char *)foo; * } */ #define BUILD_ASSERT(cond) \ do { (void) sizeof(char [1 - 2*!(cond)]); } while(0) /** * BUILD_ASSERT_OR_ZERO - assert a build-time dependency, as an expression. * @cond: the compile-time condition which must be true. * * Your compile will fail if the condition isn't true, or can't be evaluated * by the compiler. This can be used in an expression: its value is "0". * * Example: * #define foo_to_char(foo) \ * ((char *)(foo) \ * + BUILD_ASSERT_OR_ZERO(offsetof(struct foo, string) == 0)) */ #define BUILD_ASSERT_OR_ZERO(cond) \ (sizeof(char [1 - 2*!(cond)]) - 1) #endif /* CCAN_BUILD_ASSERT_H */