[tip:perf/core] perf trace: Fix build when DWARF unwind isn't available

[tip-bot for Arnaldo Carvalho de Melo]

Commit-ID:  ccd62a896ffe3dbd60f3b7570a2b74e4fe030ed6
Gitweb:     http://git.kernel.org/tip/ccd62a896ffe3dbd60f3b7570a2b74e4fe030ed6
Author:     Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
AuthorDate: Sat, 16 Apr 2016 09:36:32 -0300
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Sat, 16 Apr 2016 09:44:28 -0300

perf trace: Fix build when DWARF unwind isn't available

The variable is initialized and then conditionally set to a different
value, but not used when DWARF unwinding is not available, bummer, write
1000 times: "Run make -C tools/perf build-test"...

  builtin-trace.c: In function âcmd_traceâ:
  builtin-trace.c:3112:6: error: variable âmax_stack_user_setâ set but not
  used [-Werror=unused-but-set-variable]
    bool max_stack_user_set = true;
        ^
  cc1: all warnings being treated as err

Fix it by marking it as __maybe_unused.

Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Milian Wolff <milian.wolff@xxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Fixes: 056149932602 ("perf trace: Make --(min,max}-stack imply "--call-graph dwarf"")
Link: http://lkml.kernel.org/n/tip-85r40c5hhv6jnmph77l1hgsr@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/builtin-trace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 026ec0c..0e3c1ce 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -3109,7 +3109,7 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
 			"per thread proc mmap processing timeout in ms"),
 	OPT_END()
 	};
-	bool max_stack_user_set = true;
+	bool __maybe_unused max_stack_user_set = true;
 	bool mmap_pages_user_set = true;
 	const char * const trace_subcommands[] = { "record", NULL };
 	int err;