On Mon, 1 May 2000, Tigran Aivazian wrote:
> On Mon, 1 May 2000, Graham Stoney wrote:
>
> > In a discussion about Linux kernel optimisations, Russell King writes:
> > > Oh, if any of the mm people are reading this, what about killing the
> > > redundant zero initialisers so that these variables can be placed in
> > > the BSS?
> >
> > Even better, is there any way to get gcc to treat static and extern variables
> > with explicit all-bits-zero initializers as though they had no initializers?
> >
> > In other words, treat these the same:
> > static int initialised=0; /* wastes space in .data */
> > static int uninitialised; /* implicitly zero, and more efficient */
> >
> > This would be useful for all space-conscious environments where the user
> > knows that .bss is zero-filled. Variables with redundant explicit zero
> > initializers are effectively wasting .data space, but some programmer like
> > to use them anyway.
>
> # cd /usr/src/linux/arch/i386/kernel
> # grep -i surprise *S
> head.S: * Clear BSS first so that there are no surprises...
>
> as you see, it has been done explicitly by the kernel, regardless of what
> gcc may have prepared.
oops, I just realised you are asking for something slightly different.
What I meant is that you can now safely ignore zero-initializers because
BSS is zero-cleared by the kernel explicitly.
Regards,
Tigran
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