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

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Date:	Wed, 20 May 2015 15:29:37 +0200
From:	Martin Liška <mliska@...e.cz>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
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

On 05/20/2015 03:17 PM, Arnaldo Carvalho de Melo wrote:
> 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

Hi

GCC 4.8.0 is the first version capable of the option: https://gcc.gnu.org/gcc-4.8/changes.html.
That can be problematic, which GCC version do you support in linux/perf?

Martin

>
>> 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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