Re: [lwip-devel] Concern over strict aliasing and undefined behavior?

[Valery Ushakov]

On Mon, Oct 07, 2013 at 10:40:18 -0500, Sam Caldwell wrote:

> I am currently doing some network programming and ran into the
> problem of strict-aliasing when I wanted to cast a portion of an
> incoming buffer to a struct modeling a network header.
> Unfortunately, this violates strict-aliasing, and therefore has
> undefined behavior.  I'm looking for the most efficient way to do
> this that is correct, portable, and well-defined.
[...]
> Additionally, here is a more thorough write-up of my understanding
> of the issue as a stack-overflow question:
>
> http://stackoverflow.com/questions/19165134/correct-portable-way-to-interpret-buffer-as-a-struct

You might find Derek Jones exegesis of the C standard helpful
http://www.knosof.co.uk/cbook/cbook.html

Your original "uint8_t *" version at stackoverflow is probably ok too,
since uint8_t is pretty much guaranteed to be defined as "a character
type", the last item in the aliasing rules list in 6.5 [#7].

-uwe