1 #ifndef CCAN_CAST_IF_TYPE_H
2 #define CCAN_CAST_IF_TYPE_H
5 #if HAVE_TYPEOF && HAVE_BUILTIN_CHOOSE_EXPR && HAVE_BUILTIN_TYPES_COMPATIBLE_P
7 * cast_if_type - only cast an expression if it is of a given type
8 * @desttype: the type to cast to
9 * @expr: the expression to cast
10 * @oktype: the type we allow
12 * This macro is used to create functions which allow multiple types.
13 * The result of this macro is used somewhere that a @desttype type is
14 * expected: if @expr was of type @oktype, it will be cast to
15 * @desttype type. As a result, if @expr is any type other than
16 * @oktype or @desttype, a compiler warning will be issued.
18 * This macro can be used in static initializers.
20 * This is merely useful for warnings: if the compiler does not
21 * support the primitives required for cast_if_type(), it becomes an
22 * unconditional cast, and the @oktype argument is not used. In
23 * particular, this means that @oktype can be a type which uses
24 * the "typeof": it will not be evaluated if typeof is not supported.
27 * // We can take either an unsigned long or a void *.
28 * void _set_some_value(void *val);
29 * #define set_some_value(expr) \
30 * _set_some_value(cast_if_type(void *, (expr), unsigned long))
32 #define cast_if_type(desttype, expr, oktype) \
33 __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(expr):0), oktype), \
34 (desttype)(expr), (expr))
36 #define cast_if_type(expr, oktype, desttype) ((desttype)(expr))
40 * cast_if_any - only cast an expression if it is one of the three given types
41 * @desttype: the type to cast to
42 * @expr: the expression to cast
43 * @ok1: the first type we allow
44 * @ok2: the second type we allow
45 * @ok3: the third type we allow
47 * This is a convenient wrapper for multiple cast_if_type() calls. You can
48 * chain them inside each other (ie. use cast_if_any() for expr) if you need
49 * more than 3 arguments.
52 * // We can take either a long, unsigned long, void * or a const void *.
53 * void _set_some_value(void *val);
54 * #define set_some_value(expr) \
55 * _set_some_value(cast_if_any(void *, (expr), \
56 * long, unsigned long, const void *))
58 #define cast_if_any(desttype, expr, ok1, ok2, ok3) \
59 cast_if_type(desttype, \
60 cast_if_type(desttype, \
61 cast_if_type(desttype, (expr), ok1), \
66 * typesafe_cb - cast a callback function if it matches the arg
67 * @rtype: the return type of the callback function
68 * @fn: the callback function to cast
69 * @arg: the (pointer) argument to hand to the callback function.
71 * If a callback function takes a single argument, this macro does
72 * appropriate casts to a function which takes a single void * argument if the
73 * callback provided matches the @arg (or a const or volatile version).
75 * It is assumed that @arg is of pointer type: usually @arg is passed
76 * or assigned to a void * elsewhere anyway.
79 * void _register_callback(void (*fn)(void *arg), void *arg);
80 * #define register_callback(fn, arg) \
81 * _register_callback(typesafe_cb(void, (fn), (arg)), (arg))
83 #define typesafe_cb(rtype, fn, arg) \
84 cast_if_any(rtype (*)(void *), (fn), \
85 rtype (*)(typeof(*arg)*), \
86 rtype (*)(const typeof(*arg)*), \
87 rtype (*)(volatile typeof(*arg)*))
90 * typesafe_cb_const - cast a const callback function if it matches the arg
91 * @rtype: the return type of the callback function
92 * @fn: the callback function to cast
93 * @arg: the (pointer) argument to hand to the callback function.
95 * If a callback function takes a single argument, this macro does appropriate
96 * casts to a function which takes a single const void * argument if the
97 * callback provided matches the @arg.
99 * It is assumed that @arg is of pointer type: usually @arg is passed
100 * or assigned to a void * elsewhere anyway.
103 * void _register_callback(void (*fn)(const void *arg), const void *arg);
104 * #define register_callback(fn, arg) \
105 * _register_callback(typesafe_cb_const(void, (fn), (arg)), (arg))
107 #define typesafe_cb_const(rtype, fn, arg) \
108 cast_if_type(rtype (*)(const void *), (fn), \
109 rtype (*)(const typeof(*arg)*))
112 * typesafe_cb_preargs - cast a callback function if it matches the arg
113 * @rtype: the return type of the callback function
114 * @fn: the callback function to cast
115 * @arg: the (pointer) argument to hand to the callback function.
117 * This is a version of typesafe_cb() for callbacks that take other arguments
121 * void _register_callback(void (*fn)(int, void *arg), void *arg);
122 * #define register_callback(fn, arg) \
123 * _register_callback(typesafe_cb_preargs(void, (fn), (arg), int),\
126 #define typesafe_cb_preargs(rtype, fn, arg, ...) \
127 cast_if_any(rtype (*)(__VA_ARGS__, void *), (fn), \
128 rtype (*)(__VA_ARGS__, typeof(arg)), \
129 rtype (*)(__VA_ARGS__, const typeof(*arg) *), \
130 rtype (*)(__VA_ARGS__, volatile typeof(*arg) *))
133 * typesafe_cb_postargs - cast a callback function if it matches the arg
134 * @rtype: the return type of the callback function
135 * @fn: the callback function to cast
136 * @arg: the (pointer) argument to hand to the callback function.
138 * This is a version of typesafe_cb() for callbacks that take other arguments
142 * void _register_callback(void (*fn)(void *arg, int), void *arg);
143 * #define register_callback(fn, arg) \
144 * _register_callback(typesafe_cb_postargs(void, (fn), (arg), int),\
147 #define typesafe_cb_postargs(rtype, fn, arg, ...) \
148 cast_if_any(rtype (*)(void *, __VA_ARGS__), (fn), \
149 rtype (*)(typeof(arg), __VA_ARGS__), \
150 rtype (*)(const typeof(*arg) *, __VA_ARGS__), \
151 rtype (*)(volatile typeof(*arg) *, __VA_ARGS__))
154 * typesafe_cb_cmp - cast a compare function if it matches the arg
155 * @rtype: the return type of the callback function
156 * @fn: the callback function to cast
157 * @arg: the (pointer) argument(s) to hand to the compare function.
159 * If a callback function takes two matching-type arguments, this macro does
160 * appropriate casts to a function which takes two const void * arguments if
161 * the callback provided takes two a const pointers to @arg.
163 * It is assumed that @arg is of pointer type: usually @arg is passed
164 * or assigned to a void * elsewhere anyway.
167 * void _my_qsort(void *base, size_t nmemb, size_t size,
168 * int (*cmp)(const void *, const void *));
169 * #define my_qsort(base, nmemb, cmpfn) \
170 * _my_qsort((base), (nmemb), sizeof(*(base)), \
171 * typesafe_cb_cmp(int, (cmpfn), (base)), (arg))
173 #define typesafe_cb_cmp(rtype, cmpfn, arg) \
174 cast_if_type(rtype (*)(const void *, const void *), (cmpfn), \
175 rtype (*)(const typeof(*arg)*, const typeof(*arg)*))
177 #endif /* CCAN_CAST_IF_TYPE_H */