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Re: Xen reliance on non-standard GCC features
- To: Roberto Bagnara <roberto.bagnara@xxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 5 Jun 2023 09:35:16 +0200
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- Cc: Stefano Stabellini <stefano.stabellini@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 05 Jun 2023 07:35:39 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 05.06.2023 07:28, Roberto Bagnara wrote:
> Finally, Xen seems to rely on explicitly undefined behavior, namely
> C99 UB 58: "A structure or union is defined as containing no named
> members (6.7.2.1)." All instances but one occur via macro BUILD_BUG_ON_ZERO,
> the remaining instance concerns struct
> `cpu_policy::<anonymous union>::<anonymous struct>::<anonymous
> union>::<anonymous struct>'.
> Reliance on undefined behavior might be hard to justify.
For starters just a comment here: I'm pretty sure this case was discussed
before, and that it was agreed that if need be we'd simply add _ as the
name there. Yet then - how did you notice this? Code inspection? I would
expect no analysis tool would spot it because it's used for gcc < 4.6
only. And I doubt you run analysis tools in combination with this old a
gcc?
Jan
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