typesafe: fix warnings with gcc's -Wpointer-arith

[ccan] / ccan / typesafe_cb / typesafe_cb.h

diff --git a/ccan/typesafe_cb/typesafe_cb.h b/ccan/typesafe_cb/typesafe_cb.h
index 4aabecf53e1228bbe4d2dd3ce69b505bbfb84311..4bc2e2da9b9249e0b1626ac950846acfe9446109 100644 (file)
--- a/ccan/typesafe_cb/typesafe_cb.h
+++ b/ccan/typesafe_cb/typesafe_cb.h
@@ -12,9 +12,8 @@
  *
  * This macro is used to create functions which allow multiple types.
  * The result of this macro is used somewhere that a @desttype type is
- * expected: if @expr was of type @oktype, it will be cast to
- * @desttype type.  As a result, if @expr is any type other than
- * @oktype or @desttype, a compiler warning will be issued.
+ * expected: if @test is exactly of type @oktype, then @expr will be
+ * cast to @desttype type, otherwise left alone.
  *
  * This macro can be used in static initializers.
  *
@@ -31,7 +30,7 @@
  *             _set_some_value(cast_if_type(void *, (e), (e), unsigned long))
  */
 #define cast_if_type(desttype, expr, test, oktype)                     \
-__builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(test):0), oktype), \
+       __builtin_choose_expr(__builtin_types_compatible_p(typeof(test), oktype), \
                        (desttype)(expr), (expr))
 #else
 #define cast_if_type(desttype, expr, test, oktype) ((desttype)(expr))
@@ -79,6 +78,9 @@ __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(test):0), oktype),
  * It is assumed that @arg is of pointer type: usually @arg is passed
  * or assigned to a void * elsewhere anyway.
  *
+ * This will not work with a NULL @fn argument: see typesafe_cb_def or
+ * typesafe_cb_exact.
+ *
  * Example:
  *     void _register_callback(void (*fn)(void *arg), void *arg);
  *     #define register_callback(fn, arg) \
@@ -87,6 +89,47 @@ __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(test):0), oktype),
 #define typesafe_cb(rtype, fn, arg)                    \
        cast_if_type(rtype (*)(void *), (fn), (fn)(arg), rtype)
 
+/**
+ * typesafe_cb_def - cast a callback fn if it matches arg (of defined type)
+ * @rtype: the return type of the callback function
+ * @fn: the callback function to cast
+ * @arg: the (pointer) argument to hand to the callback function.
+ *
+ * This is typesafe_cb(), except the type must be defined (eg. if it's
+ * struct foo *, the definition of struct foo must be visible).  For many
+ * applications, this is reasonable.
+ *
+ * This variant can accept @fn equal to NULL.
+ *
+ * Example:
+ *     void _register_callback(void (*fn)(void *arg), void *arg);
+ *     #define register_callback(fn, arg) \
+ *             _register_callback(typesafe_cb_def(void, (fn), (arg)), (arg))
+ */
+#define typesafe_cb_def(rtype, fn, arg)                                \
+       cast_if_any(rtype (*)(void *), (fn), 0?(fn):(fn),       \
+                   rtype (*)(typeof(*arg)*),                   \
+                   rtype (*)(const typeof(*arg)*),             \
+                   rtype (*)(volatile typeof(*arg)*))
+
+/**
+ * typesafe_cb_exact - cast a callback fn if it exactly matches arg
+ * @rtype: the return type of the callback function
+ * @fn: the callback function to cast
+ * @arg: the (pointer) argument to hand to the callback function.
+ *
+ * This is typesafe_cb(), except the @fn can be NULL, or must exactly match
+ * the @arg type (no const or volatile).
+ *
+ * Example:
+ *     void _register_callback(void (*fn)(void *arg), void *arg);
+ *     #define register_callback(fn, arg) \
+ *             _register_callback(typesafe_cb_exact(void, (fn), (arg)), (arg))
+ */
+#define typesafe_cb_exact(rtype, fn, arg)                              \
+       cast_if_type(rtype (*)(void *), (fn), 0?(fn):(fn),              \
+                    rtype (*)(typeof(arg)))
+
 /**
  * typesafe_cb_const - cast a const callback function if it matches the arg
  * @rtype: the return type of the callback function
@@ -105,10 +148,8 @@ __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(test):0), oktype),
  *     #define register_callback(fn, arg) \
  *             _register_callback(typesafe_cb_const(void, (fn), (arg)), (arg))
  */
-#define typesafe_cb_const(rtype, fn, arg)                              \
-       sizeof((fn)((const void *)0)),                                  \
-               cast_if_type(rtype (*)(const void *),                   \
-                            (fn), (fn)(arg), rtype (*)(typeof(arg)))
+#define typesafe_cb_const(rtype, fn, arg)                      \
+       cast_if_type(rtype (*)(const void *), (fn), (fn)(arg), rtype)
 
 /**
  * typesafe_cb_preargs - cast a callback function if it matches the arg
@@ -126,8 +167,9 @@ __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(test):0), oktype),
  *                                (arg))
  */
 #define typesafe_cb_preargs(rtype, fn, arg, ...)                       \
-       cast_if_type(rtype (*)(__VA_ARGS__, void *), (fn), (fn),        \
+       cast_if_type(rtype (*)(__VA_ARGS__, void *), (fn), 0?(fn):(fn), \
                     rtype (*)(__VA_ARGS__, typeof(arg)))
+
 /**
  * typesafe_cb_postargs - cast a callback function if it matches the arg
  * @rtype: the return type of the callback function
@@ -144,8 +186,9 @@ __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(test):0), oktype),
  *                                (arg))
  */
 #define typesafe_cb_postargs(rtype, fn, arg, ...)                      \
-       cast_if_type(rtype (*)(void *, __VA_ARGS__), (fn), (fn),        \
+       cast_if_type(rtype (*)(void *, __VA_ARGS__), (fn), 0?(fn):(fn), \
                     rtype (*)(typeof(arg), __VA_ARGS__))
+
 /**
  * typesafe_cb_cmp - cast a compare function if it matches the arg
  * @rtype: the return type of the callback function
@@ -168,7 +211,8 @@ __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(test):0), oktype),
  *                       typesafe_cb_cmp(int, (cmpfn), (base)), (arg))
  */
 #define typesafe_cb_cmp(rtype, cmpfn, arg)                             \
-       cast_if_type(rtype (*)(const void *, const void *), (cmpfn),    \
+       cast_if_type(rtype (*)(const void *, const void *),             \
+                    (cmpfn), 0?(cmpfn):(cmpfn),                        \
                     rtype (*)(const typeof(*arg)*, const typeof(*arg)*))
                     
 #endif /* CCAN_CAST_IF_TYPE_H */