linux-kernel - Re: [PATCH] x86, acpi: LLVMLinux: Remove nested functions from Thinkpad ACPI

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Message-ID: <yw1xzjlw58dc.fsf@unicorn.mansr.com>
Date:	Wed, 12 Feb 2014 21:27:59 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Behan Webster <behanw@...verseincode.com>
Cc:	Christoph Hellwig <hch@...radead.org>, dl9pf@....de,
	David Woodhouse <David.Woodhouse@...el.com>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	ibm-acpi-devel@...ts.sourceforge.net,
	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86, acpi: LLVMLinux: Remove nested functions from Thinkpad ACPI

Behan Webster <behanw@...verseincode.com> writes:

> On 02/12/14 13:11, Christoph Hellwig wrote:
>> On Wed, Feb 12, 2014 at 09:58:46PM +0100, dl9pf@....de wrote:
>>> being able to compile the Linux kernel with Clang. The use of nested functions
>>> blocks this effort.
>> Is there any good way to make gcc warn about the use of nested functions?
> Interesting idea.
>
> '-Wtrampolines'
>      Warn about trampolines generated for pointers to nested functions.
>
>      A trampoline is a small piece of data or code that is created at
>      run time on the stack when the address of a nested function is
>      taken, and is used to call the nested function indirectly.  For
>      some targets, it is made up of data only and thus requires no
>      special treatment.  But, for most targets, it is made up of code
>      and thus requires the stack to be made executable in order for the
>      program to work properly.
>
> That might work.

That sounds like it will only warn if a trampoline is needed.  A nested
function whose address isn't taken, as is the case here, wouldn't
trigger this warning.

-- 
Måns Rullgård
mans@...sr.com
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