netdev - Re: [PATCH v2 1/6] net-PPP: Replacement of a printk() call by pr_warn() in mppe

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Date:	Sun, 7 Dec 2014 13:36:08 +0100 (CET)
From:	Julia Lawall <julia.lawall@...6.fr>
To:	Joe Perches <joe@...ches.com>
cc:	SF Markus Elfring <elfring@...rs.sourceforge.net>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	Paul Mackerras <paulus@...ba.org>, linux-ppp@...r.kernel.org,
	netdev@...r.kernel.org, Eric Dumazet <eric.dumazet@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH v2 1/6] net-PPP: Replacement of a printk() call by
 pr_warn() in mppe_rekey()



On Sun, 7 Dec 2014, Joe Perches wrote:

> On Sun, 2014-12-07 at 11:44 +0100, Julia Lawall wrote:
> > > A negative to that approach is inlined functions would
> > > take the function name of the parent not keep the
> > > inlined function name.
> > 
> > I tried the following:
> > 
> > #include <stdio.h>
> > 
> > inline int foo() {
> >   printf("%s %x\n",__func__,0x12345);
> > }
> > 
> > int main () {
> >   foo();
> > }
> > 
> > The assembly code generated for main is:
> > 
> > 0000000000400470 <main>:
> >   400470:       b9 45 23 01 00          mov    $0x12345,%ecx
> >   400475:       ba 4b 06 40 00          mov    $0x40064b,%edx
> >   40047a:       be 44 06 40 00          mov    $0x400644,%esi
> >   40047f:       bf 01 00 00 00          mov    $0x1,%edi
> >   400484:       31 c0                   xor    %eax,%eax
> >   400486:       e9 d5 ff ff ff          jmpq   400460 <__printf_chk@plt>
> > 
> > That is, the call to foo seems tom be inlined.
> > 
> > But the output is:
> > 
> > foo 12345
> > 
> > So it seems that __func__ is determined before inlining.
> 
> True, and that's what I intended to describe.
> 
> If you did that with a kernel module and replaced
> "%s, __func__" with "%pf, __builtin_return_address(0)"
> when built with kallsyms you should get:
> 
> "modname 12345" when most would expect "foo 12345"
> 
> when built without kallsyms, that output should be
> "<address> 12345"
> 
> but the object code should be smaller.

OK.  But the semantic patch is only using __func__ and only in cases where 
the string wanted is similar to the name of the current function, so I 
think it should be OK?

julia
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