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-rw-r--r--lib/ccan/build_assert/build_assert.h39
1 files changed, 39 insertions, 0 deletions
diff --git a/lib/ccan/build_assert/build_assert.h b/lib/ccan/build_assert/build_assert.h
new file mode 100644
index 0000000000..24e59c44cd
--- /dev/null
+++ b/lib/ccan/build_assert/build_assert.h
@@ -0,0 +1,39 @@
+#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 */