[tip:perfcounters/core] perf tools: Work around strict aliasing related warnings

tip-bot for Ingo Molnar
2009-09-02T13:01:25Z

Commit-ID: 65014ab36196f6d86edc9ee23759d6930b9d89a8
Gitweb: http://git.kernel.org/tip/65014ab36196f6d86edc9ee23759d6930b9d89a8
Author: Ingo Molnar <mingo@elte.hu>
AuthorDate: Wed, 2 Sep 2009 14:55:55 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 2 Sep 2009 14:56:33 +0200

perf tools: Work around strict aliasing related warnings

Older versions of GCC are rather stupid about strict aliasing:

util/trace-event-parse.c: In function 'parse_cmdlines':
util/trace-event-parse.c:93: warning: dereferencing type-punned pointer will break strict-aliasing rules
util/trace-event-parse.c: In function 'parse_proc_kallsyms':
util/trace-event-parse.c:155: warning: dereferencing type-punned pointer will break strict-aliasing rules
util/trace-event-parse.c:157: warning: dereferencing type-punned pointer will break strict-aliasing rules
util/trace-event-parse.c:158: warning: dereferencing type-punned pointer will break strict-aliasing rules
util/trace-event-parse.c: In function 'parse_ftrace_printk':
util/trace-event-parse.c:294: warning: dereferencing type-punned pointer will break strict-aliasing rules
util/trace-event-parse.c:295: warning: dereferencing type-punned pointer will break strict-aliasing rules
make: *** [util/trace-event-parse.o] Error 1

Make it clear to GCC that we intend with those pointers, by passing
them through via an explicit (void *) cast.

We might want to add -fno-strict-aliasing as well, like the kernel
itself does.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
tools/perf/util/trace-event-info.c | 2 +-
tools/perf/util/trace-event-parse.c | 12 ++++++------
2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/trace-event-info.c b/tools/perf/util/trace-event-info.c
index 8161527..6c9302a 100644
--- a/tools/perf/util/trace-event-info.c
+++ b/tools/perf/util/trace-event-info.c
@@ -188,7 +188,7 @@ int bigendian(void)
unsigned char str[] = { 0x1, 0x2, 0x3, 0x4, 0x0, 0x0, 0x0, 0x0};
unsigned int *ptr;

- ptr = (unsigned int *)str;
+ ptr = (unsigned int *)(void *)str;
return *ptr == 0x01020304;
}

diff --git a/tools/perf/util/trace-event-parse.c b/tools/perf/util/trace-event-parse.c
index 665dac2..37b10c2 100644
--- a/tools/perf/util/trace-event-parse.c
+++ b/tools/perf/util/trace-event-parse.c
@@ -90,7 +90,7 @@ void parse_cmdlines(char *file, int size __unused)
while (line) {
item = malloc_or_die(sizeof(*item));
sscanf(line, "%d %as", &item->pid,
- (float *)&item->comm); /* workaround gcc warning */
+ (float *)(void *)&item->comm); /* workaround gcc warning */
item->next = list;
list = item;
line = strtok_r(NULL, "\n", &next);
@@ -152,10 +152,10 @@ void parse_proc_kallsyms(char *file, unsigned int size __unused)
item = malloc_or_die(sizeof(*item));
item->mod = NULL;
ret = sscanf(line, "%as %c %as\t[%as",
- (float *)&addr_str, /* workaround gcc warning */
+ (float *)(void *)&addr_str, /* workaround gcc warning */
&ch,
- (float *)&item->func,
- (float *)&item->mod);
+ (float *)(void *)&item->func,
+ (float *)(void *)&item->mod);
item->addr = strtoull(addr_str, NULL, 16);
free(addr_str);

@@ -291,8 +291,8 @@ void parse_ftrace_printk(char *file, unsigned int size __unused)
while (line) {
item = malloc_or_die(sizeof(*item));
ret = sscanf(line, "%as : %as",
- (float *)&addr_str, /* workaround gcc warning */
- (float *)&item->printk);
+ (float *)(void *)&addr_str, /* workaround gcc warning */
+ (float *)(void *)&item->printk);
item->addr = strtoull(addr_str, NULL, 16);
free(addr_str);