lib/ccan/check_type/check_type.h

   1 #ifndef CCAN_CHECK_TYPE_H
   2 #define CCAN_CHECK_TYPE_H
   3 #include "config.h"
   4
   5 /**
   6  * check_type - issue a warning or build failure if type is not correct.
   7  * @expr: the expression whose type we should check (not evaluated).
   8  * @type: the exact type we expect the expression to be.
   9  *
  10  * This macro is usually used within other macros to try to ensure that a macro
  11  * argument is of the expected type.  No type promotion of the expression is
  12  * done: an unsigned int is not the same as an int!
  13  *
  14  * check_type() always evaluates to 0.
  15  *
  16  * If your compiler does not support typeof, then the best we can do is fail
  17  * to compile if the sizes of the types are unequal (a less complete check).
  18  *
  19  * Example:
  20  *      // They should always pass a 64-bit value to _set_some_value!
  21  *      #define set_some_value(expr)                    \
  22  *              _set_some_value((check_type((expr), uint64_t), (expr)))
  23  */
  24
  25 /**
  26  * check_types_match - issue a warning or build failure if types are not same.
  27  * @expr1: the first expression (not evaluated).
  28  * @expr2: the second expression (not evaluated).
  29  *
  30  * This macro is usually used within other macros to try to ensure that
  31  * arguments are of identical types.  No type promotion of the expressions is
  32  * done: an unsigned int is not the same as an int!
  33  *
  34  * check_types_match() always evaluates to 0.
  35  *
  36  * If your compiler does not support typeof, then the best we can do is fail
  37  * to compile if the sizes of the types are unequal (a less complete check).
  38  *
  39  * Example:
  40  *      // Do subtraction to get to enclosing type, but make sure that
  41  *      // pointer is of correct type for that member.
  42  *      #define container_of(mbr_ptr, encl_type, mbr)                   \
  43  *              (check_types_match((mbr_ptr), &((encl_type *)0)->mbr),  \
  44  *               ((encl_type *)                                         \
  45  *                ((char *)(mbr_ptr) - offsetof(enclosing_type, mbr))))
  46  */
  47 #if HAVE_TYPEOF
  48 #define check_type(expr, type)                  \
  49         ((typeof(expr) *)0 != (type *)0)
  50
  51 #define check_types_match(expr1, expr2)         \
  52         ((typeof(expr1) *)0 != (typeof(expr2) *)0)
  53 #else
  54 #include <ccan/build_assert/build_assert.h>
  55 /* Without typeof, we can only test the sizes. */
  56 #define check_type(expr, type)                                  \
  57         BUILD_ASSERT_OR_ZERO(sizeof(expr) == sizeof(type))
  58
  59 #define check_types_match(expr1, expr2)                         \
  60         BUILD_ASSERT_OR_ZERO(sizeof(expr1) == sizeof(expr2))
  61 #endif /* HAVE_TYPEOF */
  62
  63 #endif /* CCAN_CHECK_TYPE_H */