RE : [lwip-devel] SMEMCPY

[Frédéric BERNON]

There is some "memcpy" in the code, shouldn't we replace them by MEMCPY ?

 
  
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-----Message d'origine-----
De : address@hidden [mailto:address@hidden De la part de Goldschmidt Simon
Envoyé : mardi 22 janvier 2008 13:36
À : lwip-devel
Objet : RE: [lwip-devel] SMEMCPY



> 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
small."
> 
> 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).

Simon


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