linux-kernel - Re: [PATCH 2/2] Add CONFIG_READABLE

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Date:	Thu, 12 Apr 2012 22:35:17 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Andi Kleen <ak@...ux.intel.com>, Andi Kleen <andi@...stfloor.org>,
	linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
	x86@...nel.org
Subject: Re: [PATCH 2/2] Add CONFIG_READABLE_ASM

On Thu, Apr 12, 2012 at 10:17:07PM +0200, Geert Uytterhoeven wrote:
> Hi Sam,
> 
> On Thu, Apr 12, 2012 at 22:07, Sam Ravnborg <sam@...nborg.org> wrote:
> > Could you try this:
> >
> > cc-disable-opt = $(call try-run,\
> >        $(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -f$(strip $(1)) -c -xc /dev/null -o "$TMP",-fno-$(strip $(1)))
> >
> > KBUILD_CFLAGS += $(call cc-disable-opt, ipa-cp-clone)
> >
> >
> > It will try if "gcc -fipa-cp-clone" is supported,
> > and add -fno-ipa-cp-clone in that case.
> 
> Unfortunately not:
> 
> m68k-linux-gnu-gcc -Wp,-MD,kernel/.bounds.s.d  -nostdinc -isystem
> /usr/lib/gcc/m68k-linux-gnu/4.1.2/include
> -I/scratch/geert/linux/linux-next/arch/m68k/include
> Iarch/m68k/include/generated -Iinclude  -include
> /scratch/geert/linux/linux-next/include/linux/kconfig.h -D__KERNEL__
> -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing
> -fno-common -Werror-implicit-function-declaration -Wno-format-security
> -fno-delete-null-pointer-checks -Os -fno-reorder-blocks
> -fno-ipa-cp-clone -pipe -fno-strength-reduce -ffixed-a2
> -fno-omit-frame-pointer -fno-optimize-sibling-calls -g
> -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(bounds)"
> -D"KBUILD_MODNAME=KBUILD_STR(bounds)" -fverbose-asm -S -o
> kernel/bounds.s kernel/bounds.c
> cc1: error: unrecognized command line option "-fno-ipa-cp-clone"
> make[1]: *** [kernel/bounds.s] Error 1
> make: *** [prepare0] Error 2

So with the above command-line gcc fails with an exit code for -fno-ipa-cp-clone.
But with cc-option it does not.

Can you dig out the command-line used for cc-option?
We may be able to analyze why it fails in the above case, but
not with cc-option.

I wonder if we hit something strange due to the fact that we
are assigning to KBUILD_CFLAGS and we reference the same variable.

But that does not explain why the others work.

	Sam
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