generics.h

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#ifndef GENERICS_H
#define GENERICS_H
 
#if defined __has_builtin
#define var __auto_type
 
#define lf_is_same_type(a, b) __builtin_types_compatible_p(__typeof__(a), __typeof__(b))
 
#define lf_is_same(typename, b) __builtin_types_compatible_p(typename, __typeof__(b))
 
#define lf_is_type_equal(typename_a, typename_b) __builtin_types_compatible_p(typename_a, typename_b)
 
#define lf_is_pointer_or_array(p) (__builtin_classify_type(p) == 5)
 
#define lf_decay(p) (&*__builtin_choose_expr(lf_is_pointer_or_array(p), p, NULL))
 
#define lf_is_pointer(p) lf_is_same_type(p, lf_decay(p))
 
#define lf_get_pointer(p) __builtin_choose_expr(lf_is_pointer(p), p, &p)
 
#define lf_to_left_type(left, right)                                                                                   \
  __builtin_choose_expr(lf_is_pointer_or_array(left),                                                                  \
                        __builtin_choose_expr(lf_is_pointer_or_array(right), (right), &(right)),                       \
                        __builtin_choose_expr(lf_is_pointer_or_array(right), *(right), (right)))
 
#else // buitin are not available
 
#define var
#define lf_is_same_type(a, b)
#define lf_is_same(typename, b)
#define lf_is_pointer_or_array(p)
#define lf_decay(p)
#define lf_is_pointer(p)
#define lf_get_pointer(p)
#define lf_to_left_type(left, right)
 
#endif // __has_builtin
 
#endif // GENERICS_H