Re: [git pull] x86 updates for v2.6.28, phase #1

From: Linus Torvalds
Date: Fri Oct 10 2008 - 17:08:02 EST




On Fri, 10 Oct 2008, H. Peter Anvin wrote:
>
> Double underscores aren't the problem per se, the problem is having changes
> _ASM_X86_ to ASM_X86__ and therefore violating the namespace.

Yeah. If I recall the namespace rules correctly, you have to have a
underscore followed by another underscore or an upper-case letter. Those
cannot even be used for local variables by a conforming program.

Single-underscore + lower-case letter is only reserved as an external
identifier. I _think_. So a conforming program could still do

int main(int argc, char **argv)
{
int _asm_x86_types_h = 1;
return _asm_x86_types_h;
}

and I _think_ it should be ok.

So a system macro definition that could mess with something (admittedly
crazy as that) has to be either double underscores or underscore +
uppercase, so as long as the prefix is "_ASM" (or _LINUX), we're ok.

Double underscores in the _middle_ of the identifiers are a non-issue, and
are just ugly.

> That being said, I don't personally like the double underscores.

I agree, inside the identifier in particular they do seem pointless. At
the beginning, they are useful for things like __i386__ or __x86, where
you need the double underscore because 'i' is lower-case.

Or maybe I mis-remember the name space rules.

Linus
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