Fix a couple of possible divide-by-zero conditions in statistics

Several people reported the average time problem, but there's another
one lurking there too: if the dive duration is zero, you get bogus
average depth information too (but because that one was a floating point
divide, and by default they are unsignalling on x86, it didn't crash, it
just resulted in bogus results).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/statistics.c b/statistics.c
index 34f487b521398cdc025186462d1ae81e1df63314..19105653c2aa1ad8014cfa095dd86bf524f940fc 100644 (file)
--- a/statistics.c
+++ b/statistics.c
@@ -91,6 +91,18 @@ static void process_dive(struct dive *dp, stats_t *stats)
                stats->max_depth.mm = dp->maxdepth.mm;
        if (stats->min_depth.mm == 0 || dp->maxdepth.mm < stats->min_depth.mm)
                stats->min_depth.mm = dp->maxdepth.mm;
+       if (dp->watertemp.mkelvin) {
+               if (stats->min_temp == 0 || dp->watertemp.mkelvin < stats->min_temp)
+                       stats->min_temp = dp->watertemp.mkelvin;
+               if (dp->watertemp.mkelvin > stats->max_temp)
+                       stats->max_temp = dp->watertemp.mkelvin;
+               stats->combined_temp += get_temp_units(dp->watertemp.mkelvin, &unit);
+               stats->combined_count++;
+       }
+
+       /* Maybe we should drop zero-duration dives */
+       if (!dp->duration.seconds)
+               return;
        stats->avg_depth.mm = (1.0 * old_tt * stats->avg_depth.mm +
                        dp->duration.seconds * dp->meandepth.mm) / stats->total_time.seconds;
        if (dp->sac > 2800) { /* less than .1 cuft/min (2800ml/min) is bogus */
@@ -103,14 +115,6 @@ static void process_dive(struct dive *dp, stats_t *stats)
                        stats->min_sac.mliter = dp->sac;
                stats->total_sac_time = sac_time;
        }
-       if (dp->watertemp.mkelvin) {
-               if (stats->min_temp == 0 || dp->watertemp.mkelvin < stats->min_temp)
-                       stats->min_temp = dp->watertemp.mkelvin;
-               if (dp->watertemp.mkelvin > stats->max_temp)
-                       stats->max_temp = dp->watertemp.mkelvin;
-               stats->combined_temp += get_temp_units(dp->watertemp.mkelvin, &unit);
-               stats->combined_count++;
-       }
 }
 
 static void process_all_dives(struct dive *dive, struct dive **prev_dive)
@@ -266,7 +270,7 @@ static void show_single_dive_stats(struct dive *dive)
 static void show_total_dive_stats(struct dive *dive)
 {
        double value;
-       int decimals;
+       int decimals, seconds;
        const char *unit;
        stats_t *stats_ptr;
 
@@ -287,7 +291,10 @@ static void show_total_dive_stats(struct dive *dive)
                set_label(stats_w.max_temp, "%.1f %s", value, unit);
        }
        set_label(stats_w.total_time, get_time_string(stats_ptr->total_time.seconds, 0));
-       set_label(stats_w.avg_time, get_time_string(stats_ptr->total_time.seconds / stats_ptr->selection_size, 0));
+       seconds = stats_ptr->total_time.seconds;
+       if (stats_ptr->selection_size)
+               seconds /= stats_ptr->selection_size;
+       set_label(stats_w.avg_time, get_time_string(seconds, 0));
        set_label(stats_w.longest_time, get_time_string(stats_ptr->longest_time.seconds, 0));
        set_label(stats_w.shortest_time, get_time_string(stats_ptr->shortest_time.seconds, 0));
        value = get_depth_units(stats_ptr->max_depth.mm, &decimals, &unit);