linux-kernel - Re: [PATCH] frv: fix build failure

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Date:   Sun, 3 Dec 2017 22:32:26 +0000
From:   Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>
Cc:     Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] frv: fix build failure

On Mon, Nov 27, 2017 at 10:25:16AM -0800, Vineet Gupta wrote:
> +CC linux-arch, Arnd
> 
> On 11/23/2017 09:17 AM, Alexey Brodkin wrote:
> >Hi Sudip,
> >
> >On Tue, 2017-11-21 at 22:10 +0000, Sudip Mukherjee wrote:

<snip>

> I understand the case/need for adding a weak/common abort() as a
> quick fix for handling such cases, but perhaps we should not and
> instead fix the rootcause. In this specific case, Claudiu mentioned
> that gcc was generating abort due to something like this (flagging a
> possible divide by zero due to
> -fno-isolate-erroneous-paths-dereference.
> 
> a;
> 
> fn1() {
>   switch (a)
>   case 0:
>   return 1 / a;
> }
> 
> Sudeep can you confirm that removing this hacking FRV build to not
> have this toggle fixes the abort issue.
> 
> So the offending code needs to be fixed as in the end when that code
> path is taken system is hosed.

The above case that you mentioned is indeed the case here.
mpihelp_divrem() in lib/mpi/mpih-div.c has this same divide by zero case.

So, what should be the actual fix here?

--
Regards
Sudip