Re: [lwip-users] structure packaging

[address@hidden]

address@hidden wrote:
> There are some structures that are by default not packed but only work
> if they are packed.
> The following structures are:
> struct mem in mem.c
> struct pbuf in pbuf.h
> struct dhcp in dhcp.h
>
> Is there any reason that they are not packed by default? Because I think
> they should be.
> Has anyone had similar problems?
>    
Can you explain why these should be packed? Structure packing should 
only be necessary for protocol headers where the structures are used to 
describe a well-defined header layout. In contrast to this, the 
structures above are used internally only and thus don't need to be packed.

The only exception to this in the lwIP code currently is the struct 
ip_reass_helper, which is only packed to know that its size isn't 
enlarged by an optimizing compiler, but that's not valid for mem/pbuf/dhcp.

Simon