linux-kernel - RE: why use memcpy when memmove is there?

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Message-ID: <MDEHLPKNGKAHNMBLJOLKKEKAGCAC.davids@webmaster.com>
Date:	Tue, 14 Aug 2007 14:59:22 -0700
From:	"David Schwartz" <davids@...master.com>
To:	<linux-kernel@...r.kernel.org>
Subject: RE: why use memcpy when memmove is there?

> Hi, All
>
> We were looking at  "[kernel]/lib/string.c"
> (http://lxr.linux.no/source/lib/string.c#L500)
>
> memcpy copies a part of memory to some other location
> but It will not work for all cases of overlapping
> blocks.(if the start of destination block falls
> between the source block)
>
> while memove copes with overlapping areas.
>
> then why is memcpy present in the sources can't we
> simply do
>
> "#define memcpy memmove" in include/linux/string.h
>
> or am I missing something?

Suppose you have two vehicles, an economy car and a semi truck. The truck
can go everyplace the car can go, and the truck can carry a bigger load. So
why would you ever use the car? Answer: The car uses less gas and you don't
always need a truck.

Think about what it takes to be able to copy one block of memory to another
location when those locations might overlap. You don't always need that.

DS

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