out parameters - How should I check that [out] params in COM can be used? -


Officially one should not use the [out] parameters from COM functions unless The function is not successful, it means that there can be (at least) three ways to see if any [out] parameter can be used

the following Consider the interface 

  Interface IFoo: IUnknown {HRESULT GetOtherFoo ([Out] IFoo ** ppFoo); HRESULT bar (); };

Which of the following ways would you advise to use it?

Check 1 return value 

  CComPtr & lt; IFoo & gt; other; HRESULT hr = foo- & gt; GetOtherFoo (and others); If (SUCCEEDED (HR)) other-> bar ();   
  IFoo due to a bug in   NULL  pointer may cause Dirensing, it would bother me a bit I 
 
  Check the 2 output parameters  
 
 It depends on the fact that if a method fails, then it will be  [out]  Parameter (if parameter is changed & lt; ==> it is safe to use). 
 
  CComPtr & lt; IFoo & gt; other; Foo- & gt; GetOtherFoo (& amp; Other); If (other) other-> bar ();  
 
 Note that this is none anyway,  CComPtr  of destructors  Release  will call if the pointer is not < Code> NULL  therefore it can not be trash 
 
  Both in a crazy way  
 
  CComPtr & lt; IFoo & gt; Check both. other; HRESULT hr = foo- & gt; GetOtherFoo (and others); If (SUCCEEDED (HR) and others) other-> times ();  
 
 This is a bit verbose in my opinion. 
 
 
 P.S. See. 
 
 If you want to write more checks and make it more reliable, you can slow down the code. Option 3 is for you because you expect COM server There are bugs in it, it is fair enough to investigate against them.

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