[boost] Re: change to linked_ptr release

From: Gavin Collings (gcollings_at_[hidden])
Date: 2000-02-07 10:52:15

> No specific destruction order is necessary to pass around the
message. 
> The message itself is not used until there is only one node on the
> list.  So the actual node that carries it is unimportant (the circular
> list helps here).  Along as one node knows the message, it is not
lost.
>  If a node is leaving the list and has the message, it passes it on to
> its neighbor.  The direction is irrelevant.  It is true that in some
> circumstances, the message might need to be passed to evey node on the
> list, but each of these operations would be constant time.  This lazy
> evaluation allows all operations to be limited to O(1).

Ah yes, quite neat.  I haven't properly explored using the list as a
notification mechanism, this looks like a good application of it,
though.  Shall we split the difference and say N/2 on average then ;)
I'm still a little hesitant about leaving all those potentially
dangling references around, though.

> Do you have struct alignment settings leftover from some previous
> project?  MSVC's default is 8 byte alignment.

Here's what MSDN says: -

   Type Alignment
   -------------- 
   char Align on byte boundaries 
   short (16-bit) Align on even byte boundaries 
   int and long (32-bit) Align on 32-bit boundaries 
   float Align on 32-bit boundaries 
   double Align on 64-bit boundaries 
   structures Largest alignment requirement of any member 
   unions Alignment requirement of the first member 

The largest alignment requirement of any member is 4 bytes (pointer). 
The 8 bytes you're talking of is the maximum amount of padding that
will be inserted to bring about this alignment (/Zp option).  That is
set to 8 bytes in my VC project, I still get a 12 byte linked_ptr
though - apparently no padding is necessary.

Gavin.