perf tools: Use __maybe_used for unused variables

perf defines both __used and __unused variables to use for marking
unused variables. The variable __used is defined to
__attribute__((__unused__)), which contradicts the kernel definition to
__attribute__((__used__)) for new gcc versions. On Android, __used is
also defined in system headers and this leads to warnings like: warning:
'__used__' attribute ignored

__unused is not defined in the kernel and is not a standard definition.
If __unused is included everywhere instead of __used, this leads to
conflicts with glibc headers, since glibc has a variables with this name
in its headers.

The best approach is to use __maybe_unused, the definition used in the
kernel for __attribute__((unused)). In this way there is only one
definition in perf sources (instead of 2 definitions that point to the
same thing: __used and __unused) and it works on both Linux and Android.
This patch simply replaces all instances of __used and __unused with
__maybe_unused.

Signed-off-by: Irina Tirdea <irina.tirdea@intel.com>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1347315303-29906-7-git-send-email-irina.tirdea@intel.com
[ committer note: fixed up conflict with a116e05 in builtin-sched.c ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-probe.c

@@ -143,8 +143,8 @@ static int parse_probe_event_argv(int argc, const char **argv)
 	return ret;
 }
 
-static int opt_add_probe_event(const struct option *opt __used,
-			      const char *str, int unset __used)
+static int opt_add_probe_event(const struct option *opt __maybe_unused,
+			      const char *str, int unset __maybe_unused)
 {
 	if (str) {
 		params.mod_events = true;
@@ -153,8 +153,8 @@ static int opt_add_probe_event(const struct option *opt __used,
 		return 0;
 }
 
-static int opt_del_probe_event(const struct option *opt __used,
-			       const char *str, int unset __used)
+static int opt_del_probe_event(const struct option *opt __maybe_unused,
+			       const char *str, int unset __maybe_unused)
 {
 	if (str) {
 		params.mod_events = true;
@@ -166,7 +166,7 @@ static int opt_del_probe_event(const struct option *opt __used,
 }
 
 static int opt_set_target(const struct option *opt, const char *str,
-			int unset __used)
+			int unset __maybe_unused)
 {
 	int ret = -ENOENT;
 
@@ -188,8 +188,8 @@ static int opt_set_target(const struct option *opt, const char *str,
 }
 
 #ifdef DWARF_SUPPORT
-static int opt_show_lines(const struct option *opt __used,
-			  const char *str, int unset __used)
+static int opt_show_lines(const struct option *opt __maybe_unused,
+			  const char *str, int unset __maybe_unused)
 {
 	int ret = 0;
 
@@ -209,8 +209,8 @@ static int opt_show_lines(const struct option *opt __used,
 	return ret;
 }
 
-static int opt_show_vars(const struct option *opt __used,
-			 const char *str, int unset __used)
+static int opt_show_vars(const struct option *opt __maybe_unused,
+			 const char *str, int unset __maybe_unused)
 {
 	struct perf_probe_event *pev = &params.events[params.nevents];
 	int ret;
@@ -229,8 +229,8 @@ static int opt_show_vars(const struct option *opt __used,
 }
 #endif
 
-static int opt_set_filter(const struct option *opt __used,
-			  const char *str, int unset __used)
+static int opt_set_filter(const struct option *opt __maybe_unused,
+			  const char *str, int unset __maybe_unused)
 {
 	const char *err;
 
@@ -327,7 +327,7 @@ static const struct option options[] = {
 	OPT_END()
 };
 
-int cmd_probe(int argc, const char **argv, const char *prefix __used)
+int cmd_probe(int argc, const char **argv, const char *prefix __maybe_unused)
 {
 	int ret;