linux-kernel - Re: [PATCH] perf: fix wrong DEBUG configuration

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Date:	Mon, 25 May 2015 12:47:09 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Martin Liška <mliska@...e.cz>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] perf: fix wrong DEBUG configuration


* Martin Liška <mliska@...e.cz> wrote:

> Currently, GCC optimizes -O6 same as -O3 level, thus change the value
> to -O6.

s/to -O6
  to -O3

> Right optimize debugging experience is given by passing -Og to 
> compiler. Assign default value for pointers that are identified by 
> compiler as non-initialized.

s/Right optimize debugging experience is given/
  Correct debugging experience is given/

s/identified by compiler
  identified by the compiler

>  ifeq ($(DEBUG),0)
> -  CFLAGS += -O6
> +  CFLAGS += -O3
> +else
> +  CFLAGS += $(call cc-option,-Og,-O0)
>  endif

> +# try-run
> +# Usage: option = $(call try-run, $(CC)...-o "$$TMP",option-ok,otherwise)
> +# Exit code chooses option. "$$TMP" is can be used as temporary file and
> +# is automatically cleaned up.
> +try-run = $(shell set -e;		\
> +	TMP="$(TMPOUT).$$$$.tmp";	\
> +	TMPO="$(TMPOUT).$$$$.o";	\
> +	if ($(1)) >/dev/null 2>&1;	\
> +	then echo "$(2)";		\
> +	else echo "$(3)";		\
> +	fi;				\
> +	rm -f "$$TMP" "$$TMPO")
> +
> +# cc-option
> +# Usage: cflags-y += $(call cc-option,-march=winchip-c6,-march=i586)
> +
> +cc-option = $(call try-run,\
> +	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2))

Looks good to me!

Acked-by: Ingo Molnar <mingo@...nel.org>

Thanks,

	Ingo
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