perf tools: Experiment with cppcheck

Experimenting a bit using cppcheck[1], a static checker brought to my
attention by Colin, reducing the scope of some variables, reducing the
line of source code lines in the process:

$ cppcheck --enable=style tools/perf/util/thread.c
Checking tools/perf/util/thread.c...
[tools/perf/util/thread.c:17]: (style) The scope of the variable 'leader' can be reduced.
[tools/perf/util/thread.c:133]: (style) The scope of the variable 'err' can be reduced.
[tools/perf/util/thread.c:273]: (style) The scope of the variable 'err' can be reduced.

Will continue later, but these are already useful, keep them.

1: https://sourceforge.net/p/cppcheck/wiki/Home/

Cc: Adrian Hunter <[e-mail]>
Cc: Colin Ian King <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Wang Nan <[e-mail]>
Link: http://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/evlist.c

···
 static int perf_evlist__enable_event_cpu(struct perf_evlist *evlist,
 					 struct perf_evsel *evsel, int cpu)
 {
-	int thread, err;
+	int thread;
 	int nr_threads = perf_evlist__nr_threads(evlist, evsel);
 
 	if (!evsel->fd)
 		return -EINVAL;
 
 	for (thread = 0; thread < nr_threads; thread++) {
-		err = ioctl(FD(evsel, cpu, thread),
-			    PERF_EVENT_IOC_ENABLE, 0);
+		int err = ioctl(FD(evsel, cpu, thread), PERF_EVENT_IOC_ENABLE, 0);
 		if (err)
 			return err;
 	}
···
 					    struct perf_evsel *evsel,
 					    int thread)
 {
-	int cpu, err;
+	int cpu;
 	int nr_cpus = cpu_map__nr(evlist->cpus);
 
 	if (!evsel->fd)
 		return -EINVAL;
 
 	for (cpu = 0; cpu < nr_cpus; cpu++) {
-		err = ioctl(FD(evsel, cpu, thread), PERF_EVENT_IOC_ENABLE, 0);
+		int err = ioctl(FD(evsel, cpu, thread), PERF_EVENT_IOC_ENABLE, 0);
 		if (err)
 			return err;
 	}
···
 	struct perf_evsel *evsel;
 	int ncpus = cpu_map__nr(evlist->cpus);
 	int nthreads = thread_map__nr(evlist->threads);
-	int n;
 
 	evlist__for_each_entry_reverse(evlist, evsel) {
-		n = evsel->cpus ? evsel->cpus->nr : ncpus;
+		int n = evsel->cpus ? evsel->cpus->nr : ncpus;
 		perf_evsel__close(evsel, n, nthreads);
 	}
 }

tools/perf/util/evsel.c

···
 
 static int perf_evsel__alloc_fd(struct perf_evsel *evsel, int ncpus, int nthreads)
 {
-	int cpu, thread;
-
 	if (evsel->system_wide)
 		nthreads = 1;
 
 	evsel->fd = xyarray__new(ncpus, nthreads, sizeof(int));
 
 	if (evsel->fd) {
+		int cpu, thread;
 		for (cpu = 0; cpu < ncpus; cpu++) {
 			for (thread = 0; thread < nthreads; thread++) {
 				FD(evsel, cpu, thread) = -1;

tools/perf/util/machine.c

···
 					int max_stack)
 {
 	struct ip_callchain *chain = sample->callchain;
-	int chain_nr = min(max_stack, (int)chain->nr);
+	int chain_nr = min(max_stack, (int)chain->nr), i;
 	u8 cpumode = PERF_RECORD_MISC_USER;
-	int i, j, err;
 	u64 ip;
 
 	for (i = 0; i < chain_nr; i++) {
···
 	/* LBR only affects the user callchain */
 	if (i != chain_nr) {
 		struct branch_stack *lbr_stack = sample->branch_stack;
-		int lbr_nr = lbr_stack->nr;
+		int lbr_nr = lbr_stack->nr, j;
 		/*
 		 * LBR callstack can only get user call chain.
 		 * The mix_chain_nr is kernel call chain
···
 		int mix_chain_nr = i + 1 + lbr_nr + 1;
 
 		for (j = 0; j < mix_chain_nr; j++) {
+			int err;
 			if (callchain_param.order == ORDER_CALLEE) {
 				if (j < i + 1)
 					ip = chain->ips[j];

tools/perf/util/strbuf.h

···
 int strbuf_grow(struct strbuf *buf, size_t);
 
 static inline int strbuf_setlen(struct strbuf *sb, size_t len) {
-	int ret;
 	if (!sb->alloc) {
-		ret = strbuf_grow(sb, 0);
+		int ret = strbuf_grow(sb, 0);
 		if (ret)
 			return ret;
 	}

tools/perf/util/thread.c

···
 
 int thread__init_map_groups(struct thread *thread, struct machine *machine)
 {
-	struct thread *leader;
 	pid_t pid = thread->pid_;
 
 	if (pid == thread->tid || pid == -1) {
 		thread->mg = map_groups__new(machine);
 	} else {
-		leader = __machine__findnew_thread(machine, pid, pid);
+		struct thread *leader = __machine__findnew_thread(machine, pid, pid);
 		if (leader) {
 			thread->mg = map_groups__get(leader->mg);
 			thread__put(leader);
···
 		       bool exec)
 {
 	struct comm *new, *curr = thread__comm(thread);
-	int err;
 
 	/* Override the default :tid entry */
 	if (!thread->comm_set) {
-		err = comm__override(curr, str, timestamp, exec);
+		int err = comm__override(curr, str, timestamp, exec);
 		if (err)
 			return err;
 	} else {
···
 
 int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp)
 {
-	int err;
-
 	if (parent->comm_set) {
 		const char *comm = thread__comm_str(parent);
+		int err;
 		if (!comm)
 			return -ENOMEM;
 		err = thread__set_comm(thread, comm, timestamp);