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RE: [lwip-devel] SMEMCPY

From: Goldschmidt Simon
Subject: RE: [lwip-devel] SMEMCPY
Date: Tue, 22 Jan 2008 13:35:47 +0100

> SMEMCPY description is :
> "SMEMCPY: override this with care! Some compilers (e.g. gcc) can
inline a
>  * call to memcpy() if the length is known at compile time and is
> But I see some use in sockets.c like SMEMCPY(addr, &sin, *addrlen); In
this case, the size is not known at compile > time. What is the correct
use (or description) for this macro ? 

Those macros are defined because memcpy can be sped up on many platforms
(using loop unrolling / large register file etc.). But most of the time,
this involves a lengthy initialization (finding out whether src and dst
are aligned etc.).

So while in this situation, the compiler can't inline the memcpy, we
still know *addrlen is so small that it perhaps isn't worth the lengthy
initialization of the overridden MEMCPY and thus use the (perhaps)
smaller implementation of memcpy() (which SMEMCPY points to).


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