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List:       cfe-commits
Subject:    Re: [PATCH] D11948: Add some macros to abstract marking of parameters as "not null", and use them in
From:       Marshall Clow via cfe-commits <cfe-commits () lists ! llvm ! org>
Date:       2015-08-12 22:42:01
Message-ID: CAMBqOsibpKjjGxRifZ8dEAZfVFWdpozNcrQnM5cGxCDT158QmQ () mail ! gmail ! com
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On Tue, Aug 11, 2015 at 2:28 PM, Joerg Sonnenberger via cfe-commits <
cfe-commits@lists.llvm.org> wrote:

> On Tue, Aug 11, 2015 at 02:06:58PM -0700, Marshall Clow via cfe-commits
> wrote:
> > On Tue, Aug 11, 2015 at 1:34 PM, Dan Albert <danalbert@google.com>
> wrote:
> >
> > > Yeah, those sound like exactly what we want. Helping people find UB is
> > > good, but optimizing assuming we've fixed all of the UB isn't
> something we
> > > can do.
> > >
> >
> > Dan -- that's the situation you're in today.
> > GCC has done that kind of optimization for *years*.
>
> Only on platforms that use this markup. Which is exactly the point I am
> raising. The gain by this optimisation is questionable at best and it
> has created (or exposed, however you want to call it) non-trivial bugs
> in the real world. There is a reason why there is a lot of push back
> outside glibc for this markers.
>
>
I don't think that this is true.

My tests (from a previous message - run on a Mac, which does not use glibc)
show that gcc recognizes this and optimizes based on that.

-- Marshall

[Attachment #5 (text/html)]

<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Aug \
11, 2015 at 2:28 PM, Joerg Sonnenberger via cfe-commits <span dir="ltr">&lt;<a \
href="mailto:cfe-commits@lists.llvm.org" \
target="_blank">cfe-commits@lists.llvm.org</a>&gt;</span> wrote:<br><blockquote \
class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc \
solid;padding-left:1ex"><span class="">On Tue, Aug 11, 2015 at 02:06:58PM -0700, \
Marshall Clow via cfe-commits wrote:<br> &gt; On Tue, Aug 11, 2015 at 1:34 PM, Dan \
Albert &lt;<a href="mailto:danalbert@google.com">danalbert@google.com</a>&gt; \
wrote:<br> &gt;<br>
&gt; &gt; Yeah, those sound like exactly what we want. Helping people find UB is<br>
&gt; &gt; good, but optimizing assuming we&#39;ve fixed all of the UB isn&#39;t \
something we<br> &gt; &gt; can do.<br>
&gt; &gt;<br>
&gt;<br>
&gt; Dan -- that&#39;s the situation you&#39;re in today.<br>
&gt; GCC has done that kind of optimization for *years*.<br>
<br>
</span>Only on platforms that use this markup. Which is exactly the point I am<br>
raising. The gain by this optimisation is questionable at best and it<br>
has created (or exposed, however you want to call it) non-trivial bugs<br>
in the real world. There is a reason why there is a lot of push back<br>
outside glibc for this markers.<br><br></blockquote><div><br></div><div>I don&#39;t \
think that this is true.</div><div><br></div><div>My tests (from a previous message - \
run on a Mac, which does not use glibc) show that gcc recognizes this and optimizes \
based on that.</div><div><br></div><div>-- Marshall</div><div>  \
</div></div><br></div></div>


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