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 <[email protected]>
Acked-by: Pekka Enberg <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Steven Rostedt <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
[ committer note: fixed up conflict with a116e05 in builtin-sched.c ]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 3 insertions, 2 deletions

diff --git a/tools/perf/ui/gtk/browser.c b/tools/perf/ui/gtk/browser.c
index 3c16ab50e0f8..55acba6e0df4 100644
--- a/tools/perf/ui/gtk/browser.c
+++ b/tools/perf/ui/gtk/browser.c
@@ -237,8 +237,9 @@ static GtkWidget *perf_gtk__setup_statusbar(void)
 
 int perf_evlist__gtk_browse_hists(struct perf_evlist *evlist,
 				  const char *help,
-				  void (*timer) (void *arg)__used,
-				  void *arg __used, int delay_secs __used)
+				  void (*timer) (void *arg)__maybe_unused,
+				  void *arg __maybe_unused,
+				  int delay_secs __maybe_unused)
 {
 	struct perf_evsel *pos;
 	GtkWidget *vbox;