[Xen-devel] Re: [PATCH] Re: [Xen-staging] [xen-unstable] Explicitly tag every anonymous aggregate in the public headers.

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 28/3/08 21:04, "Alex Williamson" <alex.williamson@xxxxxx> wrote:

>    My previous fix allowed this to build on ia64, but it turns out
> there's still a boot issue that I don't understand.  As is, we take a
> nested dtlb fault on boot, which hg bisect determines is caused by this
> patch.  From a simple test program, I can verify that only the outermost
> __extension__ is necessary to include code w/ -std=c99.  So embedding an
> __extension__ within an __extension__ isn't necessary, but I don't know
> why it actually changes the behavior of the code.  The patch below
> reverts a few chucks of this cset and gets us booting again.  FWIW, I'm
> using gcc-4.1.2.  Thanks,

Playing around with this a bit I can't see what changes for having nested
usage of __extension__. I'm using gcc 4.1 but on x86_64.

Could you play around with sizeof() and offsetof() and find out exactly
what's getting laid out differently? Maybe we'll have to do some of the
reversion that you suggest (or just revert the whole lot and assert __GNUC__
and !__STRICT_ANSI__ at the top of the file). But it'd be nice to know a bit
more about what's going on here.

 -- Keir



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