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: NIngo Molnar <mingo@elte.hu>

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;
 }
 

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);