+/*
+ * Generate a mask of type `type` with the `length` least significant bits
+ * set, and the most significant bits cleared.
+ */
+#define _bt_make_mask(type, length) \
+ ((type) ~_bt_make_mask_complement(type, length))
+
+/*
+ * Right shift a value `v` of `shift` bits.
+ *
+ * The type of `v` can be signed or unsigned integer.
+ * The value of `shift` must be less than the size of `v` (in bits),
+ * otherwise the behavior is undefined.
+ * Evaluates to the result of the shift operation.
+ *
+ * According to the C99 standard, right shift of a left hand-side signed
+ * type which has a negative value is implementation defined. This
+ * bitfield header relies on the right shift implementation carrying the
+ * sign bit. If the compiler implementation has a different behavior,
+ * emulate carrying the sign bit.
+ *
+ * This macro should not be used if `shift` can be greater or equal than
+ * the bitwidth of `v`. See `_bt_safe_rshift`.
+ */
+#if ((-1 >> 1) == -1)
+#define _bt_rshift(v, shift) ((v) >> (shift))
+#else
+#define _bt_rshift(v, shift) \
+ ((__typeof__(v)) ((_bt_cast_value_to_unsigned(v) >> (shift)) | \
+ ((v) < 0 ? _bt_make_mask_complement(__typeof__(v), \
+ sizeof(v) * CHAR_BIT - (shift)) : 0)))