[ipxe-devel] [PATCH 1/1] [intel] Add PCI device IDs for Intel I218-LM and I218-V

[Michael Brown]

On 28/01/16 13:06, Thomas Miletich wrote:
> @Michael: somewhat OT, but there seems to be an unreachable call
>> intel_destroy_ring ( intel, &intel->rx );
>
> in intel_open()

Yes, that's the error recovery code to undo the effects of 
intel_create_ring(...->rx).  My usual pattern for error handling is:


   if ( ( rc = try_thing_one() ) != 0 )
      goto err_thing_one;

   ...

   if ( ( rc = try_thing_two() ) != 0 )
      goto err_thing_two;

   ...
   ...

   return 0;

   ...

   undo_thing_two();
  err_thing_two:

   ...

   undo_thing_one();
  err_thing_one:

   ...

   return rc

This means that the error recovery code is always present when the code 
is first written.  In future, when try_thing_three() is added to the 
function, the developer doesn't need to remember to add the logically 
unrelated undo_thing_two().

The error recovery code for the latest possible error in the function 
will always be unreachable with this design pattern.

Michael