SERVER-39490 opWriteConcernCounters can cause undefined behavior due to overflow

(cherry picked from commit 884ac2862eda54e15d99e4db253b822cb4a90f1d)

2 files changed, 8 insertions, 8 deletions

diff --git a/src/mongo/db/stats/server_write_concern_metrics.cpp b/src/mongo/db/stats/server_write_concern_metrics.cpp
index da8e74c9011..1477dac2f61 100644
--- a/src/mongo/db/stats/server_write_concern_metrics.cpp
+++ b/src/mongo/db/stats/server_write_concern_metrics.cpp
@@ -133,21 +133,21 @@ void ServerWriteConcernMetrics::WriteConcernMetricsForOperationType::recordWrite
 
 void ServerWriteConcernMetrics::WriteConcernMetricsForOperationType::toBSON(
     BSONObjBuilder* builder) const {
-    builder->append("wmajority", wMajorityCount);
+    builder->append("wmajority", static_cast<long long>(wMajorityCount));
 
     BSONObjBuilder wNumBuilder(builder->subobjStart("wnum"));
     for (auto const& pair : wNumCounts) {
-        wNumBuilder.append(std::to_string(pair.first), pair.second);
+        wNumBuilder.append(std::to_string(pair.first), static_cast<long long>(pair.second));
     }
     wNumBuilder.done();
 
     BSONObjBuilder wTagBuilder(builder->subobjStart("wtag"));
     for (auto const& pair : wTagCounts) {
-        wTagBuilder.append(pair.first, pair.second);
+        wTagBuilder.append(pair.first, static_cast<long long>(pair.second));
     }
     wTagBuilder.done();
 
-    builder->append("none", noWCount);
+    builder->append("none", static_cast<long long>(noWCount));
 }
 
 namespace {
diff --git a/src/mongo/db/stats/server_write_concern_metrics.h b/src/mongo/db/stats/server_write_concern_metrics.h
index 9a9525d1b30..e2744de9abe 100644
--- a/src/mongo/db/stats/server_write_concern_metrics.h
+++ b/src/mongo/db/stats/server_write_concern_metrics.h
@@ -84,16 +84,16 @@ private:
         void toBSON(BSONObjBuilder* builder) const;
 
         // Count of operations with writeConcern w:"majority".
-        long long wMajorityCount = 0;
+        std::uint64_t wMajorityCount = 0;
 
         // Count of operations without a writeConcern "w" value.
-        long long noWCount = 0;
+        std::uint64_t noWCount = 0;
 
         // Counts of operations with writeConcern w:<num>.
-        std::map<int, long long> wNumCounts;
+        std::map<int, std::uint64_t> wNumCounts;
 
         // Counts of operations with writeConcern w:"tag".
-        StringMap<long long> wTagCounts;
+        StringMap<std::uint64_t> wTagCounts;
     };
 
     mutable stdx::mutex _mutex;