Re: [Qemu-devel] [PATCH] HACKING: remove bogus restrictions

[Michael S. Tsirkin]

On Tue, Aug 28, 2012 at 06:23:38PM +0100, Peter Maydell wrote:
> On 28 August 2012 18:18, Michael S. Tsirkin <address@hidden> wrote:
> > On Tue, Aug 28, 2012 at 05:24:40PM +0100, Peter Maydell wrote:
> >>  C99 7.1.3
> >> reserves underscore capital and double underscore prefixes.
> >
> > This is taking it out of context - reserved means different
> > things in different parts of the spec.
> >
> > As far as I can see, 7.1.3 talks about what is permissible in headers:
> > naturally when a libc implementation adds stuff in a header it would
> > want to avoid breaking applications including this header. But
> > it does not talk about what is permissible in a legal program - to avoid
> > conflicts, you just need to use variables with reasonable names like
> > kvmXXX qemuXXX or virtioXXX.
> 
> 7.1.3 para 2 says "If the program declares or defines an identifier
> in a context in which it is reserved [...] the behavior is undefined."
> The rationale for 7.1.3 says that the underscore-cap and double
> underscore identifiers are "reserved for the implementor" and that
> "part of the name space of internal identifiers beginning with
> underscore is available to the user" which implies that the rest
> of that namespace is *not* available to the user.
> 
> I think that's fairly clear that we can't use these identifiers
> without entering the realm of undefined behavior.
> 

I'll have to re-read that, I missed it.
What about _t in POSIX? That seems fairly safe if name is long and qemu
specific enough.

-- 
MST