Re: [PATCH] perf: fix wrong DEBUG configuration

[Martin Liška]

On 05/20/2015 04:55 PM, Ingo Molnar wrote:

* Arnaldo Carvalho de Melo <a...@kernel.org> wrote:

Em Wed, May 20, 2015 at 03:29:37PM +0200, Martin Liška escreveu:

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:

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?

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?

So the rule has been: What are the kernel requirements for the
toolchain? tools/perf/ should build with that.

So we could use -Og if it works, like Kbuild does it:

         KBUILD_CFLAGS += $(call cc-option,-mno-fp-ret-in-387)

the 'cc-option' Make function does some magic of silently calling GCC
with that option and observing the result.

See:

   scripts/Kbuild.include:cc-option = $(call try-run,\

et al.

Thanks,

        Ingo

Hi.

I am sorry, I did mistake in understanding of DEBUG variable.
Following patch should be fixed, except missing auto-detection
of -Og option.

Unfortunately, following hunk does not work, no -Ox is added to CFLAGS?

--  CFLAGS += -Og
++  CFLAGS += $(call cc-option,-Og,-O0)


Thanks,
Martin

>From 98ef10fcb27afc3ae7aaab3ebd157ab90b3b1afe Mon Sep 17 00:00:00 2001
From: mliska <mli...@suse.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, thus change the value
to -O6.
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 <mli...@suse.cz>
---
 tools/perf/arch/common.c            | 2 +-
 tools/perf/config/Makefile          | 4 +++-
 tools/perf/util/symbol.c            | 2 +-
 tools/perf/util/trace-event-parse.c | 2 +-
 4 files changed, 6 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..6a29320 100644
--- a/tools/perf/config/Makefile
+++ b/tools/perf/config/Makefile
@@ -129,7 +129,9 @@ ifndef DEBUG
 endif
 
 ifeq ($(DEBUG),0)
-  CFLAGS += -O6
+  CFLAGS += -O3
+else
+  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