linux-kernel - Re: [tip:x86/tdx 8/12] vmlinux.o: warning: objtool: __tdx_hypercall+0x128: __tdx_hypercall_failed() is missing a _

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Date:   Thu, 14 Sep 2023 16:16:47 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     "Huang, Kai" <kai.huang@...el.com>, lkp <lkp@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "oe-kbuild-all@...ts.linux.dev" <oe-kbuild-all@...ts.linux.dev>,
        "x86@...nel.org" <x86@...nel.org>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>
Subject: Re: [tip:x86/tdx 8/12] vmlinux.o: warning: objtool:
 __tdx_hypercall+0x128: __tdx_hypercall_failed() is missing a __noreturn
 annotation


* Peter Zijlstra <peterz@...radead.org> wrote:

> > It appears the __noreturn must be annotated to the function declaration 
> > but not the function body.  I'll send out the fix as soon as I confirm 
> > the fix with LKP.
> 
> FWIW, the reason being that...
> 
> The point of noreturn is that the caller should know to stop generating 
> code. For that the declaration needs the attribute, because call sites 
> typically do not have access to the function definition in C.

BTW., arguably shouldn't the compiler generate a warning to begin with, 
when it encounters a noreturn function definition whose prototype doesn't 
have the attribute?

Thanks,

	Ingo