uftrace: Fix dead store warnings found by infer

This patch fixes some dead store warnings found by a static analysis
tool, called infer[1].

The warning messages are as follows.

  $ cd /path/to/uftrace
  $ infer run --force-integration make
          ...
  #24
  utils/debug.c:386: error: Dead Store
    The value written to `&percent` (type `double`) is never used.
    384. void print_diff_percent(uint64_t base_nsec, uint64_t pair_nsec)
    385. {
    386. 	double percent = 999.99;
          ^

  #28
  utils/debug.c:387: error: Dead Store
    The value written to `&sc` is never used.
    385. {
    386.  double percent = 999.99;
    387.  const char *sc = get_color(COLOR_CODE_NORMAL);
          ^
    388.  const char *ec = get_color(COLOR_CODE_RESET);
    389.

  #31
  utils/kernel.c:57: error: Dead Store
    The value written to `&ret` is never used.
    55. {
    56.   struct kfilter *pos, *tmp;
    57.   int ret = -1;
         ^
    58.   int fd;
    59.

  #32
  utils/perf.c:230: error: Dead Store
    The value written to `&start` is never used.
    228.  buf = &data[start & mask];
    229.  size = end - start;
    230.  start += size;
          ^

And fix warning on compile time with including unistd.h
header file.

  utils/kernel-parser.c:151:9:
  warning: implicit declaration of function 'close';
  did you mean 'pclos'?
  [-Wimplicit-function-declaration]
    151 |         close(kp->fds[cpu]);
        |         ^~~~~
        |         pclose

[1] https://github.com/facebook/infer

Fixed: #1553
Signed-off-by: Paran Lee <p4ranlee@gmail.com>

utils/debug.c

@@ -383,8 +383,8 @@ void print_time_unit(uint64_t delta_nsec)
 
 void print_diff_percent(uint64_t base_nsec, uint64_t pair_nsec)
 {
-	double percent = 999.99;
-	const char *sc = get_color(COLOR_CODE_NORMAL);
+	double percent;
+	const char *sc;
 	const char *ec = get_color(COLOR_CODE_RESET);
 
 	if (base_nsec == 0) {
@@ -401,10 +401,8 @@ void print_diff_percent(uint64_t base_nsec, uint64_t pair_nsec)
 	percent = 100.0 * (int64_t)(pair_nsec - base_nsec) / base_nsec;
 
 	/* for some error cases */
-	if (percent > 999.99)
+	if (percent > 999.99 || percent < -999.99)
 		percent = 999.99;
-	else if (percent < -999.99)
-		percent = -999.99;
 
 	sc = percent > 30  ? get_color(COLOR_CODE_RED) :
 	     percent > 3   ? get_color(COLOR_CODE_MAGENTA) :

utils/kernel-parser.c

@@ -4,6 +4,7 @@
 #include <string.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
+#include <unistd.h>
 
 /* This should be defined before #include "utils.h" */
 #define PR_FMT "kernel"

utils/kernel.c

@@ -43,7 +43,6 @@ struct kfilter {
 static int set_filter_file(const char *filter_file, struct list_head *filters)
 {
 	struct kfilter *pos, *tmp;
-	int ret = -1;
 	int fd;
 
 	fd = open_tracing_file(filter_file, true);
@@ -64,10 +63,9 @@ static int set_filter_file(const char *filter_file, struct list_head *filters)
 		if (write(fd, " ", 1) != 1)
 			pr_dbg2("writing filter file failed, but ignoring...\n");
 	}
-	ret = 0;
 
 	close(fd);
-	return ret;
+	return 0;
 }
 
 static int set_tracing_filter(struct uftrace_kernel_writer *kernel)

utils/perf.c

@@ -227,7 +227,6 @@ void record_perf_data(struct uftrace_perf_writer *perf, int cpu, int sock)
 
 	buf = &data[start & mask];
 	size = end - start;
-	start += size;
 
 	if (sock > 0)
 		send_trace_perf_data(sock, cpu, buf, size);