linux-kernel - Re: String literals in _

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Date:	Thu, 26 Mar 2015 15:15:57 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Joe Perches <joe@...ches.com>
Cc:	gcc@....gnu.org, Mathias Krause <minipli@...glemail.com>,
	Mason <slash.tmp@...e.fr>,
	Linux ARM <linux-arm-kernel@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: String literals in __init functions

On Thu, 26 Mar 2015 14:58:40 -0700 Joe Perches <joe@...ches.com> wrote:

> > I'd have thought that a function-wide
> > 	__attribute__((__string_section__(foo))
> > wouldn't be a ton of work to implement.
> 
> Maybe not.
> 
> Could some future version of gcc move string constants
> in a function to a specific section marked in a manner
> similar to what Andrew described above?

One thing which might complexicate this is

void foo()
{
	p("bar");
}

void  __attribute__((__string_section__(.init.rodata)) zot()
{
	p("bar");
}

It would be silly to create two instances of "bar".

Change it thusly:


#define __mark_str(str) \
	({ static const char var[] __attribute__((__section__(".init.string"))) = str; var; })

void foo()
{
	p("bar");
}

void zot()
{
	p(__mark_str("bar"));
}


and we indeed get two copies of "bar".

It would be nice not to do that, but I guess that losing this
optimization is a reasonable compromise.
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