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Message-ID: <d50f136d8ea93fe4252e43e50b3dc72c@dragora.org>
Date: Sun, 11 May 2014 17:20:55 -0300
From: "Matias A. Fonzo" <selk@...gora.org>
To: musl@...ts.openwall.com
Subject: Re: Broken GCC versions: 4.8.2 and 4.9.0
Hi dalias,
On 2014-05-11 13:19, Rich Felker wrote:
> On Sun, May 11, 2014 at 06:10:20PM +0200, Thomas Petazzoni wrote:
>>
>> On Sat, 10 May 2014 21:05:03 -0400, Rich Felker wrote:
>>
>> > It's come to my attention that GCC versions 4.8.2 and 4.9.0 are
>> > performing invalid optimizations that result in a broken musl
>> > libc.a/libc.so. It's not clear yet whether there's a good workaround,
>> > or whether we should attempt to work around the problem, so for now,
>> > please just be aware that these versions of GCC cannot be used to
>> > compile musl. Using them to compile programs against musl should not
>> > be a problem. I'll post more details later. The short version is that
>> > it's making incorrect assumptions about the reachability of global
>> > variables that have a local weak definition and an external strong
>> > one.
>>
>> Hum, interesting. I've recently tested gcc 4.8.2 + musl on ARM, and
>> gcc
>> 4.9.0 + musl on i386, and I could boot a minimal musl+Busybox system
>> under Qemu perfectly fine. Maybe the problem you refer to only affects
>> certain parts of libc.a/libc.so?
>
> I've filed the bug report which you can see here:
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61144
>
> Something like the following command should confirm whether your build
> is affected:
>
> nm src/stdio/fflush.o | grep stdout
>
> For broken gcc versions, there is no output. For non-broken ones, you
> should see something like:
>
> 00000000 V __stdout_used
I can confirm that I'm getting in Dragora (binutils 2.23.2, GCC 4.8.2 +
musl 1.1.0):
0000000000000000 V __stdout_used
I was getting scared.. :-)
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