linux-kernel - Re: [PATCH v6 4/25] compiler-gcc{3,4}.h: Use GCC

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Date:	Mon, 1 Oct 2012 13:32:25 -0700
From:	Josh Triplett <josh@...htriplett.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Daniel Santos <daniel.santos@...ox.com>,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-sparse@...r.kernel.org,
	Akinobu Mita <akinobu.mita@...il.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Christopher Li <sparse@...isli.org>,
	David Daney <david.daney@...ium.com>,
	David Howells <dhowells@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	David Woodhouse <David.Woodhouse@...el.com>,
	Don Zickus <dzickus@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v6 4/25] compiler-gcc{3,4}.h: Use GCC_VERSION macro

On Mon, Oct 01, 2012 at 12:39:44PM -0700, Andrew Morton wrote:
> On Thu, 27 Sep 2012 20:54:20 -0500
> Daniel Santos <daniel.santos@...ox.com> wrote:
> 
> > Using GCC_VERSION reduces complexity, is easier to read and is GCC's
> > recommended mechanism for doing version checks. (Just don't ask me why
> > they didn't define it in the first place.)  This also makes it easy to
> > merge compiler-gcc{3,4}.h should somebody want to.
> > 
> > Signed-off-by: Daniel Santos <daniel.santos@...ox.com>
> > ---
> >  include/linux/compiler-gcc3.h |    8 ++++----
> >  include/linux/compiler-gcc4.h |   14 +++++++-------
> >  2 files changed, 11 insertions(+), 11 deletions(-)
> > 
> > diff --git a/include/linux/compiler-gcc3.h b/include/linux/compiler-gcc3.h
> > index 37d4124..7d89feb 100644
> > --- a/include/linux/compiler-gcc3.h
> > +++ b/include/linux/compiler-gcc3.h
> > @@ -2,22 +2,22 @@
> >  #error "Please don't include <linux/compiler-gcc3.h> directly, include <linux/compiler.h> instead."
> >  #endif
> >  
> > -#if __GNUC_MINOR__ < 2
> > +#if GCC_VERSION < 30200
> >  # error Sorry, your compiler is too old - please upgrade it.
> >  #endif
> >  
> > -#if __GNUC_MINOR__ >= 3
> > +#if GCC_VERSION >= 30300
> >  # define __used			__attribute__((__used__))
> >  #else
> >  # define __used			__attribute__((__unused__))
> >  #endif
> >  
> > -#if __GNUC_MINOR__ >= 4
> > +#if GCC_VERSION >= 30400
> >  #define __must_check		__attribute__((warn_unused_result))
> >  #endif
> >  
> >  #ifdef CONFIG_GCOV_KERNEL
> > -# if __GNUC_MINOR__ < 4
> > +# if GCC_VERSION < 30400
> >  #   error "GCOV profiling support for gcc versions below 3.4 not included"
> >  # endif /* __GNUC_MINOR__ */
> >  #endif /* CONFIG_GCOV_KERNEL */
> > diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h
> > index 4506d65..b44307d 100644
> > --- a/include/linux/compiler-gcc4.h
> > +++ b/include/linux/compiler-gcc4.h
> > @@ -4,7 +4,7 @@
> >  
> >  /* GCC 4.1.[01] miscompiles __weak */
> >  #ifdef __KERNEL__
> > -# if __GNUC_MINOR__ == 1 && __GNUC_PATCHLEVEL__ <= 1
> > +# if GCC_VERSION >= 40100 &&  GCC_VERSION <= 40101
> >  //#  error Your version of gcc miscompiles the __weak directive
> >  # endif
> >  #endif
> > @@ -13,11 +13,11 @@
> >  #define __must_check 		__attribute__((warn_unused_result))
> >  #define __compiler_offsetof(a,b) __builtin_offsetof(a,b)
> >  
> > -#if __GNUC_MINOR__ > 0
> > +#if GCC_VERSION >= 40102
> 
> Is this correct (and clear)?  I'd expect
> 
> 	#if GCC_VERSION > 40000

GCC_VERSION >= 40100, actually; __GNUC_MINOR__ > 0 implies
__GNUC_MINOR__ >= 1, whereas the version you wrote would accept 4.0.1.

- Josh Triplett
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