perf tools: Work around strict aliasing related warnings
Ingo Molnar [Wed, 2 Sep 2009 12:55:55 +0000 (14:55 +0200)]
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
tools/perf/util/trace-event-parse.c

index 8161527..6c9302a 100644 (file)
@@ -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;
 }
 
index 665dac2..37b10c2 100644 (file)
@@ -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);