Prepare for release: rename to ponghero and pull in ccan.

[ponghero.git] / ccan / check_type / check_type.h

diff --git a/ccan/check_type/check_type.h b/ccan/check_type/check_type.h
new file mode 100644 (file)
index 0000000..e05236f
--- /dev/null
+++ b/ccan/check_type/check_type.h
@@ -0,0 +1,63 @@
+#ifndef CCAN_CHECK_TYPE_H
+#define CCAN_CHECK_TYPE_H
+#include "config.h"
+
+/**
+ * check_type - issue a warning or build failure if type is not correct.
+ * @expr: the expression whose type we should check (not evaluated).
+ * @type: the exact type we expect the expression to be.
+ *
+ * This macro is usually used within other macros to try to ensure that a macro
+ * argument is of the expected type.  No type promotion of the expression is
+ * done: an unsigned int is not the same as an int!
+ *
+ * check_type() always evaluates to 1.
+ *
+ * If your compiler does not support typeof, then the best we can do is fail
+ * to compile if the sizes of the types are unequal (a less complete check).
+ *
+ * Example:
+ *     // They should always pass a 64-bit value to _set_some_value!
+ *     #define set_some_value(expr)                    \
+ *             _set_some_value((check_type((expr), uint64_t), (expr)))
+ */
+
+/**
+ * check_types_match - issue a warning or build failure if types are not same.
+ * @expr1: the first expression (not evaluated).
+ * @expr2: the second expression (not evaluated).
+ *
+ * This macro is usually used within other macros to try to ensure that
+ * arguments are of identical types.  No type promotion of the expressions is
+ * done: an unsigned int is not the same as an int!
+ *
+ * check_types_match() always evaluates to 1.
+ *
+ * If your compiler does not support typeof, then the best we can do is fail
+ * to compile if the sizes of the types are unequal (a less complete check).
+ *
+ * Example:
+ *     // Do subtraction to get to enclosing type, but make sure that
+ *     // pointer is of correct type for that member. 
+ *     #define container_of(mbr_ptr, encl_type, mbr)                   \
+ *             (check_types_match((mbr_ptr), &((encl_type *)0)->mbr),  \
+ *              ((encl_type *)                                         \
+ *               ((char *)(mbr_ptr) - offsetof(enclosing_type, mbr))))
+ */
+#if HAVE_TYPEOF
+#define check_type(expr, type)                 \
+       ((typeof(expr) *)0 != (type *)0)
+
+#define check_types_match(expr1, expr2)                \
+       ((typeof(expr1) *)0 != (typeof(expr2) *)0)
+#else
+#include "build_assert/build_assert.h"
+/* Without typeof, we can only test the sizes. */
+#define check_type(expr, type)                                 \
+       EXPR_BUILD_ASSERT(sizeof(expr) == sizeof(type))
+
+#define check_types_match(expr1, expr2)                                \
+       EXPR_BUILD_ASSERT(sizeof(expr1) == sizeof(expr2))
+#endif /* HAVE_TYPEOF */
+
+#endif /* CCAN_CHECK_TYPE_H */