Re: [Xen-devel] [PATCH v6 1/4] xen: introduce SYMBOL

[Julien Grall <julien.grall@xxxxxxx>]

Hi Jan,

On 18/01/2019 09:54, Jan Beulich wrote:
> > > > On 18.01.19 at 02:24, <sstabellini@xxxxxxxxxx> wrote:
> > On Thu, 17 Jan 2019, Jan Beulich wrote:
> > > > > > On 17.01.19 at 01:37, <sstabellini@xxxxxxxxxx> wrote:
> > > > On Wed, 16 Jan 2019, Jan Beulich wrote:
> Stop. No. We very much can prove they are - _end points at
> one past the last element of _start[]. It is the compiler which
> can't prove the opposite, and hence it can't leverage
> undefined behavior for optimization purposes.
You keep saying the compiler can't leverage it for optimization purpose, however 
there are confirmations that GCC may actually leverage it (e.g [1]). You 
actually need to trick the compiler to avoid the optimization (e.g RELOC_HIDE).
So obviously, this is not only a MISRA "problem" as you state here and below.

I believe Stefano, Stewart and I provided plenty of documentation/thread to 
support our positions. Can you provide us documentation/thread showing the 
compiler will not try to leverage that case?
Cheers,

[1] 
https://kristerw.blogspot.com/2016/12/pointer-comparison-invalid-optimization.html?m=1
--
Julien Grall

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