3 files changed, 90 insertions, 0 deletions
diff --git a/ccan/ccan/build_assert/LICENSE b/ccan/ccan/build_assert/LICENSE
new file mode 120000
index 0000000..b7951da
--- /dev/null
+++ b/ccan/ccan/build_assert/LICENSE
@@ -0,0 +1 @@
+../../licenses/CC0
+\ No newline at end of file
diff --git a/ccan/ccan/build_assert/_info b/ccan/ccan/build_assert/_info
new file mode 100644
index 0000000..97ebe6c
--- /dev/null
+++ b/ccan/ccan/build_assert/_info
@@ -0,0 +1,49 @@
+#include "config.h"
+#include <stdio.h>
+#include <string.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: CC0 (Public domain)
+ * 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;
+}
diff --git a/ccan/ccan/build_assert/build_assert.h b/ccan/ccan/build_assert/build_assert.h
new file mode 100644
index 0000000..b9ecd84
--- /dev/null
+++ b/ccan/ccan/build_assert/build_assert.h
@@ -0,0 +1,40 @@
+/* CC0 (Public domain) - see LICENSE 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 */