From mboxrd@z Thu Jan  1 00:00:00 1970
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References: <27721ec6eb1f2bf4019349b1013e6d26@quintile.net>
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From: Charles Forsyth <charles.forsyth@gmail.com>
Date: Thu, 25 Jul 2019 12:59:57 +0100
Message-ID: <CAOw7k5h7sgZ+jrr3MAJuLPX-dLSzW=p-zAwPwkGKAMOdRFvPMw@mail.gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
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Subject: Re: [9fans] 5c bug
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5c shouldn't discard the cast, which implies a mask, but you should also
rewrite the code as you suggest.
(it's not just 5c, since it's the same for several other RISCy ones.)


On Thu, Jul 25, 2019 at 12:20 PM Steve Simon <steve@quintile.net> wrote:

> Hi,
>
> I traced a long standing cifs issue to 5c the compiler.
>
> The code in lib9p to validate wstat calls
> uses a neat bit of casting which fails when using 5c.
>
> /sys/src/lib9p/srv.c:658-669
>
> These following lines missfire reporting type or qid change
> when trying to rename files over cifs.
>
>         if((ushort)~r->d.type){
>         ...
>         if((uchar)~r->d.qid.type || .. ){
>
> but rewriting them like this makes the code work as expected:
>
>         if(r->d.type != (ushort)~0){
>         ...
>         if(r->d.qid.type != (uchar)~0 || ... )
>
> Personally I am happy to hack lib9p but the worry is that
> this bug might be affecting other things.
>
> I have no knowledge of the internals of the compilers so
> I am afraid I have made no attempt to dig deeper.
>
> -Steve
>
>

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<div dir=3D"ltr">5c shouldn&#39;t discard the cast, which implies a mask, b=
ut you should also rewrite the code as you suggest.<div>(it&#39;s not just =
5c, since it&#39;s the same for several other RISCy ones.)</div><div><br></=
div></div><br><div class=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_at=
tr">On Thu, Jul 25, 2019 at 12:20 PM Steve Simon &lt;<a href=3D"mailto:stev=
e@quintile.net">steve@quintile.net</a>&gt; wrote:<br></div><blockquote clas=
s=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid r=
gb(204,204,204);padding-left:1ex">Hi,<br>
<br>
I traced a long standing cifs issue to 5c the compiler.<br>
<br>
The code in lib9p to validate wstat calls<br>
uses a neat bit of casting which fails when using 5c.<br>
<br>
/sys/src/lib9p/srv.c:658-669<br>
<br>
These following lines missfire reporting type or qid change<br>
when trying to rename files over cifs.<br>
<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 if((ushort)~r-&gt;d.type){<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ...<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 if((uchar)~r-&gt;d.qid.type || .. ){<br>
<br>
but rewriting them like this makes the code work as expected:<br>
<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 if(r-&gt;d.type !=3D (ushort)~0){<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ...<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 if(r-&gt;d.qid.type !=3D (uchar)~0 || ... )<br>
<br>
Personally I am happy to hack lib9p but the worry is that<br>
this bug might be affecting other things.<br>
<br>
I have no knowledge of the internals of the compilers so<br>
I am afraid I have made no attempt to dig deeper.<br>
<br>
-Steve<br>
<br>
</blockquote></div>

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