On Wed, Jun 27, 2007 at 10:45:55AM -0700, Linus Torvalds wrote:
>
>
> On Wed, 27 Jun 2007, Al Viro wrote:
> >
> > Eh... I'd say that my variant for offsetof() is simply better - it usually
> > directly turns into EXPR_VALUE, right in place, without rather convoluted
> > work. Aside of "should such cast be a constant integer expression"...
>
> Umm. But sparse is meant to parse C code. Which very much includes *other*
> projects.
>
> The kernel, for example, has its own offsetof. And yes, these days we use
> "__compiler_offsetof()", but we used to do
>
> #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
>
> and I seriously doubt that the kernel is the only one doing things like
> that.
You can't have it both way, really. If we are talking about annotating
a codebase we _can_ annotate, that one is not a problem at all. If we
are talking about vanilla C project that never heard about sparse...
We can define whatever extensions we like, but such project has to
cope with whatever C compilers they had been using.
So "sparse believes that this defintion of offsetof can be used as
array size" will mean fsck-all outside of #ifdef __CHECKER__ and
under such ifdef we can always define it to builtin; if anything,
that will be faster and easier on sparse.
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