linux-kernel - Re: [2.6 patch] blackfin: "extern inline" -> "static inline"

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Date:	Thu, 25 Oct 2007 16:20:20 -0400
From:	"Mike Frysinger" <vapier.adi@...il.com>
To:	"Adrian Bunk" <bunk@...nel.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	"Jie Zhang" <jzhang.linux@...il.com>, bryan.wu@...log.com,
	linux-kernel@...r.kernel.org
Subject: Re: [2.6 patch] blackfin: "extern inline" -> "static inline"

On 10/25/07, Adrian Bunk <bunk@...nel.org> wrote:
> On Thu, Oct 25, 2007 at 04:07:45PM -0400, Mike Frysinger wrote:
> > On 10/25/07, Adrian Bunk <bunk@...nel.org> wrote:
> > > On Thu, Oct 25, 2007 at 12:16:40PM -0400, Mike Frysinger wrote:
> > > > On 10/25/07, Adrian Bunk <bunk@...nel.org> wrote:
> > > > > On Wed, Oct 24, 2007 at 08:06:14PM -0700, H. Peter Anvin wrote:
> > > > > > Mike Frysinger wrote:
> > > > > >> we'll have to either use the gcc attributes to force old inline
> > > > > >> behavior or use the gcc flag to force it
> > > > > >
> > > > > > We should probably have an extern_inline define then, assuming this is a
> > > > > > function that does exist in a linkable version already -- otherwise "static
> > > > > > inline" is correct.
> > > > >
> > > > > Since we #define inline to be __attribute__((always_inline))
> > > > > "extern inline" with the old semantics would only behave differently
> > > > > if someone took the address of one of these string functions.
> > > >
> > > > that isnt what we intended ;)
> > > >
> > > > > Does this happen anywhere in the blackfin port?
> > > >
> > > > gcc is also free to ignore the optimized inline in favor of an
> > > > external reference
> > >
> > > It is not since we #define inline to be __attribute__((always_inline)).
> >
> > as i said, that was not what we intended ... and actually,
> > always_inline does not mean always inline ... it is still possible to
> > get gcc to not inline things when building debug versions.
>
> Do you have any example for your claim "to get gcc to not inline things
> when building debug versions"?

$ cat test.c
__attribute__((always_inline)) int foo(void) { return 0; }
int main(void){ return foo(); }
$ gcc -g test.c -o test
$ readelf -s test | grep FUNC | grep -v _
    61: 00000000004004b8    11 FUNC    GLOBAL DEFAULT   13 foo
    68: 00000000004004c3    11 FUNC    GLOBAL DEFAULT   13 main

looks pretty straightforward to me
-mike
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