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

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Message-ID: <20150520131748.GC2955@kernel.org>
Date:	Wed, 20 May 2015 10:17:48 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Martin Liška <mliska@...e.cz>
Cc:	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

Em Wed, May 20, 2015 at 03:07:39PM +0200, Martin Liška escreveu:
> On 05/19/2015 04:04 PM, Arnaldo Carvalho de Melo wrote:
> >Em Tue, May 19, 2015 at 03:41:03PM +0200, Martin Liška escreveu:
> >>Following patch is fix for wrong DEBUG configuration.
> >
> >Can you please state, in the changelog, what you think is wrong and how
> >your proposed change fixes it, so that after reading your intent I can
> >go and look at the code to see if it matches that?

Ok, that improved things, thanks! A question:

> 
> Currently, GCC optimizes -O6 same as -O3 level. Right optimize debugging
> experience is given by passing -Og to compiler.

Is this is this -Og available in old gcc versions? When was it
introduced? Do you know?

- Arnaldo

> Assign default value for pointers that are identified by compiler as
> non-initialized.
> 
> Signed-off-by: Martin Liska <mliska@...e.cz>

> >From b5f2b42b279ab497e92d41e1f4021dd5cb6ae3ce Mon Sep 17 00:00:00 2001
> From: mliska <mliska@...e.cz>
> Date: Thu, 2 Apr 2015 15:24:49 +0200
> Subject: [PATCH] perf: fix wrong DEBUG configuration
> 
> Currently, GCC optimizes -O6 same as -O3 level. Right optimize debugging
> experience is given by passing -Og to compiler.
> Assign default value for pointers that are identified by compiler as
> non-initialized.
> 
> Signed-off-by: Martin Liska <mliska@...e.cz>
> ---
>  tools/perf/arch/common.c            | 2 +-
>  tools/perf/config/Makefile          | 2 +-
>  tools/perf/util/symbol.c            | 2 +-
>  tools/perf/util/trace-event-parse.c | 2 +-
>  4 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/perf/arch/common.c b/tools/perf/arch/common.c
> index 49776f1..b7bb42c 100644
> --- a/tools/perf/arch/common.c
> +++ b/tools/perf/arch/common.c
> @@ -61,7 +61,7 @@ const char *const mips_triplets[] = {
>  static bool lookup_path(char *name)
>  {
>  	bool found = false;
> -	char *path, *tmp;
> +	char *path, *tmp = NULL;
>  	char buf[PATH_MAX];
>  	char *env = getenv("PATH");
>  
> diff --git a/tools/perf/config/Makefile b/tools/perf/config/Makefile
> index e3b3724..ca8d3e3 100644
> --- a/tools/perf/config/Makefile
> +++ b/tools/perf/config/Makefile
> @@ -129,7 +129,7 @@ ifndef DEBUG
>  endif
>  
>  ifeq ($(DEBUG),0)
> -  CFLAGS += -O6
> +  CFLAGS += -Og
>  endif
>  
>  ifdef PARSER_DEBUG
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index 82a31fd..a19fbd4 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -400,7 +400,7 @@ static struct symbol *symbols__find_by_name(struct rb_root *symbols,
>  					    const char *name)
>  {
>  	struct rb_node *n;
> -	struct symbol_name_rb_node *s;
> +	struct symbol_name_rb_node *s = NULL;
>  
>  	if (symbols == NULL)
>  		return NULL;
> diff --git a/tools/perf/util/trace-event-parse.c b/tools/perf/util/trace-event-parse.c
> index 25d6c73..d495741 100644
> --- a/tools/perf/util/trace-event-parse.c
> +++ b/tools/perf/util/trace-event-parse.c
> @@ -173,7 +173,7 @@ void parse_ftrace_printk(struct pevent *pevent,
>  	char *line;
>  	char *next = NULL;
>  	char *addr_str;
> -	char *fmt;
> +	char *fmt = NULL;
>  
>  	line = strtok_r(file, "\n", &next);
>  	while (line) {
> -- 
> 2.1.4
> 

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