memcpy

memcpy

[Stoyan Gaydarov]

I wanted to know what memcpy returned as a result, and if it 
needs/should be checked. There are several places in the kernel where i 
noticed it being used but i also saw a warning about the result not 
being used, so i wanted to know a little more about it.

-Stoyan

Re: memcpy

[Peter Hüwe]

Am Donnerstag 27 August 2009 00:18:28 schrieb Stoyan Gaydarov:
> I wanted to know what memcpy returned as a result, and if it
> needs/should be checked. There are several places in the kernel where i
> noticed it being used but i also saw a warning about the result not
> being used, so i wanted to know a little more about it.
>
> -Stoyan
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Hi,

*memcpy is defined in .../lib/string.c  (+ some macros etc - use cscope to 
find more references) as

/**
 * memcpy - Copy one area of memory to another
 * @dest: Where to copy to
 * @src: Where to copy from
 * @count: The size of the area.
 *
 * You should not use this function to access IO space, use memcpy_toio()
 * or memcpy_fromio() instead.
 */
void *memcpy(void *dest, const void *src, size_t count)
{
    char *tmp = dest;
    const char *s = src;

    while (count--)
        *tmp++ = *s++;
    return dest;
}

You can see it just returns the destination address that you have passed to it
-> so I guess unless it is possible that you have already passed it a null 
pointer (which might horribly fail) it is not really necessary to check the 
result.


Peter

Re: memcpy

[Bernd Petrovitsch]

On Mit, 2009-08-26 at 17:18 -0500, Stoyan Gaydarov wrote:
> I wanted to know what memcpy returned as a result, and if it 
> needs/should be checked. There are several places in the kernel where i 
It is IMHO agreed concensus that kernel-implementations of well-known
(and especially C-library) userspace functions have to behave the
same/similar.
Or they get another name if only to avoid confusion.

> noticed it being used but i also saw a warning about the result not 
> being used, so i wanted to know a little more about it.

Use the source, Luke.

	Bernd
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