linux-kernel - Re: [UML] 3.16 build without optimization fails

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Date:	Tue, 19 Aug 2014 22:19:58 +0200
From:	Thomas Meyer <thomas@...3r.de>
To:	Valdis.Kletnieks@...edu
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [UML] 3.16 build without optimization fails

Hi.

Thanks for your answer.

There goes my plan to better understand an UML kernel lock up by using a debugger... Everything gets optimised out with -O2 :-(

Can you give an example function that relies on this GCC feature?

With kind regards
Thomas

Am 19.08.2014 22:06 schrieb Valdis.Kletnieks@...edu:
>
> On Tue, 19 Aug 2014 21:12:10 +0200, Thomas Meyer said: 
> > > Hi, 
> > > 
> > > the build with -O0 fails with: 
>
> > > bug or feature? 
> > > 
> > > any ideas? 
>
> Feature.  The kernel is *known* to not build with -O0, because that 
> disables *all* function inlining, and there's several functions that *have* 
> to be inlined in order to function properly (most notably, anything 
> that uses the gcc __builtin_return_address in a function that is expected 
> to be inlined).