On Thu, 8 Dec 2022 at 22:15, Michael D Kinney <michael.d.kin...@intel.com> wrote: > > Hi Ard, > > There is a difference between returning a pointer to a device path > and modifying the device path contents. > > If you add CONST to the argument, then an updated pointer to a device > path can not be returned. >
No, this is incorrect. The function takes a pointer (1) to a pointer(2) to a device path protocol EFI_DEVICE_PATH_PROTOCOL ** So the function can dereference pointer 1 and modify pointer 2 *unless* it is marked as CONST, i.e. EFI_DEVICE_PATH_PROTOCOL * CONST * in which case the pointer is not modifiable, but it is permitted to dereference that pointer to modify the underlying object. I am arguing that the prototype should be EFI_DEVICE_PATH_PROTOCOL CONST ** (which is the same as putting the CONST at the beginning) where the caller's pointer can be advanced by the callee via the pointer-to-pointer. But that would still not permit the object to be modified. > The API clear describes returning an updated device path pointer, so > the API is declared correctly without CONST. > The pointer may be updated but not the object. It really comes down to the difference between CONST EFI_DEVICE_PATH_PROTOCOL ** EFI_DEVICE_PATH_PROTOCOL CONST ** EFI_DEVICE_PATH_PROTOCOL * CONST * EFI_DEVICE_PATH_PROTOCOL **CONST (where the first two mean the same thing0 > The API does not state that the contents of the device path are modified. > > An API that uses CONST EFI_DEVICE_PATH* would indicate that the API > should not modify the contents of the device path. For example: > > /** > Returns the size of a device path in bytes. > > This function returns the size, in bytes, of the device path data structure > specified by DevicePath including the end of device path node. > If DevicePath is NULL or invalid, then 0 is returned. > > @param DevicePath A pointer to a device path data structure. > > @retval 0 If DevicePath is NULL or invalid. > @retval Others The size of a device path in bytes. > > **/ > UINTN > EFIAPI > GetDevicePathSize ( > IN CONST EFI_DEVICE_PATH_PROTOCOL *DevicePath > ); > Yes, but this one is a pointer, not a pointer-to-pointer. Big difference. -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#97149): https://edk2.groups.io/g/devel/message/97149 Mute This Topic: https://groups.io/mt/95518373/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
