dsound/tests: DirectSound3DListener_QueryInterface should accept IKsPropertySet

[Joerg-Cyril.Hoehle at t-systems.com]

Hi,

I don't know how others feel about this pattern:
+   ok(rc==DS_OK && temp_buffer!=NULL, ...
+   if(temp_buffer) IKsPropertySet_Release(temp_buffer);

I'd rather code like this
    if (rc==DS_OK && temp_buffer) Release().

The reason is that the typical invariant is
"Any output variable is correctly set if and only
 if the called function indicated success on return".
And the corollar:
If it failed, output variables may generally be filled with garbage.

Similarly, access errno only after an I/O function returned failure.

I do not dispute that it is good style for the callee to only set output
variables when returning success. But that is a requirement hard to maintain
in SW and often violated.

E.g. there's a lot of code like:
  ...
  if (some) return ERROR;
  *outparam1= xyz;
  ...
  if (more) return ERROR;
  ...
  *outparam2= abc;
  ...
  return SUCCESS;
See how p1 may contain garbage?

Regards,
 Jörg Höhle