Norman James | 6a58a27 | 2015-10-07 14:34:16 -0500 | [diff] [blame] | 1 | #include <stdio.h> |
| 2 | #include <string.h> |
| 3 | #include "config.h" |
| 4 | |
| 5 | /** |
| 6 | * build_assert - routines for build-time assertions |
| 7 | * |
| 8 | * This code provides routines which will cause compilation to fail should some |
| 9 | * assertion be untrue: such failures are preferable to run-time assertions, |
| 10 | * but much more limited since they can only depends on compile-time constants. |
| 11 | * |
| 12 | * These assertions are most useful when two parts of the code must be kept in |
| 13 | * sync: it is better to avoid such cases if possible, but seconds best is to |
| 14 | * detect invalid changes at build time. |
| 15 | * |
| 16 | * For example, a tricky piece of code might rely on a certain element being at |
| 17 | * the start of the structure. To ensure that future changes don't break it, |
| 18 | * you would catch such changes in your code like so: |
| 19 | * |
| 20 | * Example: |
| 21 | * #include <stddef.h> |
| 22 | * #include <ccan/build_assert/build_assert.h> |
| 23 | * |
| 24 | * struct foo { |
| 25 | * char string[5]; |
| 26 | * int x; |
| 27 | * }; |
| 28 | * |
| 29 | * static char *foo_string(struct foo *foo) |
| 30 | * { |
| 31 | * // This trick requires that the string be first in the structure |
| 32 | * BUILD_ASSERT(offsetof(struct foo, string) == 0); |
| 33 | * return (char *)foo; |
| 34 | * } |
| 35 | * |
| 36 | * License: CC0 (Public domain) |
| 37 | * Author: Rusty Russell <rusty@rustcorp.com.au> |
| 38 | */ |
| 39 | int main(int argc, char *argv[]) |
| 40 | { |
| 41 | if (argc != 2) |
| 42 | return 1; |
| 43 | |
| 44 | if (strcmp(argv[1], "depends") == 0) |
| 45 | /* Nothing. */ |
| 46 | return 0; |
| 47 | |
| 48 | return 1; |
| 49 | } |