Move modules to ccan/ tools to tools/

[ccan] / ccan / build_assert / build_assert.h

diff --git a/ccan/build_assert/build_assert.h b/ccan/build_assert/build_assert.h
new file mode 100644 (file)
index 0000000..4b0d75e
--- /dev/null
+++ b/ccan/build_assert/build_assert.h
@@ -0,0 +1,37 @@
+#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:
+ *     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)
+
+/**
+ * EXPR_BUILD_ASSERT - 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)                                         \
+ *               + EXPR_BUILD_ASSERT(offsetof(struct foo, string) == 0))
+ */
+#define EXPR_BUILD_ASSERT(cond) \
+       (sizeof(char [1 - 2*!(cond)]) - 1)
+
+#endif /* CCAN_BUILD_ASSERT_H */