removing bcopy... because it's half broken - fa.linux.kernel

Message from discussion removing bcopy... because it's half broken

Adrian Bunk

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More options Jan 10 2005, 4:00 am

Newsgroups: fa.linux.kernel

From: Adrian Bunk <b...@stusta.de>

Date: Mon, 10 Jan 2005 09:00:09 GMT

Local: Mon, Jan 10 2005 4:00 am

Subject: Re: removing bcopy... because it's half broken

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On Sun, Jan 09, 2005 at 12:19:09PM -0800, Linus Torvalds wrote:

> On Sun, 9 Jan 2005, Arjan van de Ven wrote:

> > Instead of fixing this inconsistency, I decided to remove it entirely,
> > explicit memcpy() and memmove() are prefered anyway (welcome to the 1990's)
> > and nothing in the kernel is using these functions, so this saves code size
> > as well for everyone.

> The problem is that at least some gcc versions would historically generate
> calls to "bcopy" on alpha for structure assignments. Maybe it doesn't any
> more, and no such old gcc versions exist any more, but who knows?
>...

include/asm-alpha/string.h says:

/*
* GCC of any recent vintage doesn't do stupid things with bcopy.
* EGCS 1.1 knows all about expanding memcpy inline, others don't.
*
* Similarly for a memset with data = 0.
*/

And Arjan's patch is pretty low-risk:

If it breaks on any architecture with any supported compiler (>= 2.95),
it will break at compile time and there will pretty fast be reports of
this breakage in which case it would be easy to revert his patch.

> Linus

cu
Adrian

"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed

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