linux-kernel - [PATCH 1/3] perf: tools: Fix aliasing violation in zfree uses

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Date:	Wed, 15 Jan 2014 10:44:06 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Ingo Molnar <mingo@...hat.com>
Cc:	Will Deacon <will.deacon@....com>,
	Mark Rutland <mark.rutland@....com>
Subject: [PATCH 1/3] perf: tools: Fix aliasing violation in zfree uses

Commit 74cf249d5cf7 (perf tools: Use zfree to help detect
use after free bugs) changed many uses of free to zfree, which
automatically clears the pointer. However, in a couple of places it
casts a const char** to void**, which the compiler doesn't like:

  cc1: warnings being treated as errors
  util/strlist.c: In function ‘str_node__delete’:
  util/strlist.c:42: error: dereferencing type-punned pointer will break strict-aliasing rules
  util/strlist.c:42: error: dereferencing type-punned pointer will break strict-aliasing rules
  make[1]: *** [util/strlist.o] Error 1

This patch fixes the issue by only throwing away the const, casting to char**
instead. This is more readily accepted by the compiler.

Signed-off-by: Mark Rutland <mark.rutland@....com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...stprotocols.net>
---
 tools/perf/util/srcline.c | 4 ++--
 tools/perf/util/strlist.c | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/srcline.c b/tools/perf/util/srcline.c
index 7e67879..f3e4bc5 100644
--- a/tools/perf/util/srcline.c
+++ b/tools/perf/util/srcline.c
@@ -129,7 +129,7 @@ static struct a2l_data *addr2line_init(const char *path)
 
 out:
 	if (a2l) {
-		zfree((void **)&a2l->input);
+		zfree((char **)&a2l->input);
 		free(a2l);
 	}
 	bfd_close(abfd);
@@ -140,7 +140,7 @@ static void addr2line_cleanup(struct a2l_data *a2l)
 {
 	if (a2l->abfd)
 		bfd_close(a2l->abfd);
-	zfree((void **)&a2l->input);
+	zfree((char **)&a2l->input);
 	zfree(&a2l->syms);
 	free(a2l);
 }
diff --git a/tools/perf/util/strlist.c b/tools/perf/util/strlist.c
index 61a90bf..71f9d10 100644
--- a/tools/perf/util/strlist.c
+++ b/tools/perf/util/strlist.c
@@ -39,7 +39,7 @@ out_delete:
 static void str_node__delete(struct str_node *snode, bool dupstr)
 {
 	if (dupstr)
-		zfree((void **)&snode->s);
+		zfree((char **)&snode->s);
 	free(snode);
 }
 
-- 
1.8.1.1

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