Re: [Qemu-devel] [PATCH v2 2/4] qga: Fix an enum conversion warningin commands-win32.c, hit by clang.

[driver1998]

On 5/1/19 2:25 AM, Eric Blake wrote:
> This adds lots of explicit casts. Are they actually necessary? Without
> seeing the actual warning, it seems fishy to have to be this explicit.

So here are the warnings, on clang version 9.0.0 (trunk 351977).

qga/commands-win32.c:461:24: error: implicit conversion from enumeration type 
'enum GuestDiskBusType' to different
      enumeration type 'STORAGE_BUS_TYPE' (aka 'enum _STORAGE_BUS_TYPE') 
[-Werror,-Wenum-conversion]
    [BusTypeUnknown] = GUEST_DISK_BUS_TYPE_UNKNOWN,
                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~
qga/commands-win32.c:462:21: error: implicit conversion from enumeration type 
'enum GuestDiskBusType' to different
      enumeration type 'STORAGE_BUS_TYPE' (aka 'enum _STORAGE_BUS_TYPE') 
[-Werror,-Wenum-conversion]
    [BusTypeScsi] = GUEST_DISK_BUS_TYPE_SCSI,
                    ^~~~~~~~~~~~~~~~~~~~~~~~
qga/commands-win32.c:463:22: error: implicit conversion from enumeration type 
'enum GuestDiskBusType' to different
      enumeration type 'STORAGE_BUS_TYPE' (aka 'enum _STORAGE_BUS_TYPE') 
[-Werror,-Wenum-conversion]
    [BusTypeAtapi] = GUEST_DISK_BUS_TYPE_IDE,
                     ^~~~~~~~~~~~~~~~~~~~~~~
qga/commands-win32.c:464:20: error: implicit conversion from enumeration type 
'enum GuestDiskBusType' to different
      enumeration type 'STORAGE_BUS_TYPE' (aka 'enum _STORAGE_BUS_TYPE') 
[-Werror,-Wenum-conversion]
    [BusTypeAta] = GUEST_DISK_BUS_TYPE_IDE,
                   ^~~~~~~~~~~~~~~~~~~~~~~
qga/commands-win32.c:465:21: error: implicit conversion from enumeration type 
'enum GuestDiskBusType' to different
      enumeration type 'STORAGE_BUS_TYPE' (aka 'enum _STORAGE_BUS_TYPE') 
[-Werror,-Wenum-conversion]
    [BusType1394] = GUEST_DISK_BUS_TYPE_IEEE1394,
                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
qga/commands-win32.c:466:20: error: implicit conversion from enumeration type 
'enum GuestDiskBusType' to different
      enumeration type 'STORAGE_BUS_TYPE' (aka 'enum _STORAGE_BUS_TYPE') 
[-Werror,-Wenum-conversion]
    [BusTypeSsa] = GUEST_DISK_BUS_TYPE_SSA,
                   ^~~~~~~~~~~~~~~~~~~~~~~
qga/commands-win32.c:467:22: error: implicit conversion from enumeration type 
'enum GuestDiskBusType' to different
      enumeration type 'STORAGE_BUS_TYPE' (aka 'enum _STORAGE_BUS_TYPE') 
[-Werror,-Wenum-conversion]
    [BusTypeFibre] = GUEST_DISK_BUS_TYPE_SSA,
                     ^~~~~~~~~~~~~~~~~~~~~~~
qga/commands-win32.c:468:20: error: implicit conversion from enumeration type 
'enum GuestDiskBusType' to different
      enumeration type 'STORAGE_BUS_TYPE' (aka 'enum _STORAGE_BUS_TYPE') 
[-Werror,-Wenum-conversion]
    [BusTypeUsb] = GUEST_DISK_BUS_TYPE_USB,
                   ^~~~~~~~~~~~~~~~~~~~~~~
qga/commands-win32.c:469:21: error: implicit conversion from enumeration type 
'enum GuestDiskBusType' to different
      enumeration type 'STORAGE_BUS_TYPE' (aka 'enum _STORAGE_BUS_TYPE') 
[-Werror,-Wenum-conversion]
    [BusTypeRAID] = GUEST_DISK_BUS_TYPE_RAID,
                    ^~~~~~~~~~~~~~~~~~~~~~~~
qga/commands-win32.c:470:22: error: implicit conversion from enumeration type 
'enum GuestDiskBusType' to different
      enumeration type 'STORAGE_BUS_TYPE' (aka 'enum _STORAGE_BUS_TYPE') 
[-Werror,-Wenum-conversion]
    [BusTypeiScsi] = GUEST_DISK_BUS_TYPE_ISCSI,
  CC      qga/qapi-generated/qga-qapi-visit.o
                     ^~~~~~~~~~~~~~~~~~~~~~~~~
qga/commands-win32.c:471:20: error: implicit conversion from enumeration type 
'enum GuestDiskBusType' to different
      enumeration type 'STORAGE_BUS_TYPE' (aka 'enum _STORAGE_BUS_TYPE') 
[-Werror,-Wenum-conversion]
    [BusTypeSas] = GUEST_DISK_BUS_TYPE_SAS,
                   ^~~~~~~~~~~~~~~~~~~~~~~
qga/commands-win32.c:472:21: error: implicit conversion from enumeration type 
'enum GuestDiskBusType' to different
      enumeration type 'STORAGE_BUS_TYPE' (aka 'enum _STORAGE_BUS_TYPE') 
[-Werror,-Wenum-conversion]
    [BusTypeSata] = GUEST_DISK_BUS_TYPE_SATA,
                    ^~~~~~~~~~~~~~~~~~~~~~~~
qga/commands-win32.c:473:20: error: implicit conversion from enumeration type 
'enum GuestDiskBusType' to different
      enumeration type 'STORAGE_BUS_TYPE' (aka 'enum _STORAGE_BUS_TYPE') 
[-Werror,-Wenum-conversion]
    [BusTypeSd] =  GUEST_DISK_BUS_TYPE_SD,
                   ^~~~~~~~~~~~~~~~~~~~~~
qga/commands-win32.c:474:20: error: implicit conversion from enumeration type 
'enum GuestDiskBusType' to different
      enumeration type 'STORAGE_BUS_TYPE' (aka 'enum _STORAGE_BUS_TYPE') 
[-Werror,-Wenum-conversion]
    [BusTypeMmc] = GUEST_DISK_BUS_TYPE_MMC,
                   ^~~~~~~~~~~~~~~~~~~~~~~
qga/commands-win32.c:486:12: error: implicit conversion from enumeration type 
'STORAGE_BUS_TYPE'
      (aka 'enum _STORAGE_BUS_TYPE') to different enumeration type 
'GuestDiskBusType' (aka 'enum GuestDiskBusType')
      [-Werror,-Wenum-conversion]
    return win2qemu[(int)bus];
    ~~~~~~ ^~~~~~~~~~~~~~~~~~

> Or is it complaining that GuestDiskBusType and STORAGE_BUS_TYPE are
> distinct types, and that we are indeed cross-assigning between the two
> enums because we intentionally want them to share values?

It looks like it is, according to the last warning.