1 files changed, 49 insertions, 0 deletions
diff --git a/lib/ccan/build_assert/_info b/lib/ccan/build_assert/_info
new file mode 100644
index 0000000000..0906af07e6
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+++ b/lib/ccan/build_assert/_info
@@ -0,0 +1,49 @@
+#include <stdio.h>
+#include <string.h>
+#include "config.h"
+
+/**
+ * build_assert - routines for build-time assertions
+ *
+ * This code provides routines which will cause compilation to fail should some
+ * assertion be untrue: such failures are preferable to run-time assertions,
+ * but much more limited since they can only depends on compile-time constants.
+ *
+ * These assertions are most useful when two parts of the code must be kept in
+ * sync: it is better to avoid such cases if possible, but seconds best is to
+ * detect invalid changes at build time.
+ *
+ * For example, a tricky piece of code might rely on a certain element being at
+ * the start of the structure.  To ensure that future changes don't break it,
+ * you would catch such changes in your code like so:
+ *
+ * Example:
+ *	#include <stddef.h>
+ *	#include <ccan/build_assert/build_assert.h>
+ *
+ *	struct foo {
+ *		char string[5];
+ *		int x;
+ *	};
+ *
+ *	static char *foo_string(struct foo *foo)
+ *	{
+ *		// This trick requires that the string be first in the structure
+ *		BUILD_ASSERT(offsetof(struct foo, string) == 0);
+ *		return (char *)foo;
+ *	}
+ *
+ * License: LGPL (2 or any later version)
+ * Author: Rusty Russell <rusty@rustcorp.com.au>
+ */
+int main(int argc, char *argv[])
+{
+	if (argc != 2)
+		return 1;
+
+	if (strcmp(argv[1], "depends") == 0)
+		/* Nothing. */
+		return 0;
+
+	return 1;
+}