Fix output time in metrics OStream exporter (#1346)

exporters/ostream/src/metric_exporter.cc

@@ -14,7 +14,34 @@ namespace
 std::string timeToString(opentelemetry::common::SystemTimestamp time_stamp)
 {
  std::time_t epoch_time = std::chrono::system_clock::to_time_t(time_stamp);
- return std::ctime(&epoch_time);
+
+ struct tm *tm_ptr = nullptr;
+# if defined(_MSC_VER)
+ struct tm buf_tm;
+ if (!gmtime_s(&buf_tm, &epoch_time))
+ {
+ tm_ptr = &buf_tm;
+ }
+# else
+ tm_ptr = std::gmtime(&epoch_time);
+# endif
+
+ char buf[100];
+ char *date_str = nullptr;
+ if (tm_ptr == nullptr)
+ {
+ OTEL_INTERNAL_LOG_ERROR("[OStream Metric] gmtime failed for " << epoch_time);
+ }
+ else if (std::strftime(buf, sizeof(buf), "%c", tm_ptr) > 0)
+ {
+ date_str = buf;
+ }
+ else
+ {
+ OTEL_INTERNAL_LOG_ERROR("[OStream Metric] strftime failed for " << epoch_time);
+ }
+
+ return std::string{date_str};
 }
 } // namespace
 
@@ -68,8 +95,8 @@ void OStreamMetricExporter::printInstrumentationInfoMetricData(
  for (const auto &record : info_metric.metric_data_)
  {
  sout_ << "\n start time\t: " << timeToString(record.start_ts)
- << " end time\t: " << timeToString(record.end_ts)
- << " description\t: " << record.instrument_descriptor.description_
+ << "\n end time\t: " << timeToString(record.end_ts)
+ << "\n description\t: " << record.instrument_descriptor.description_
  << "\n unit\t\t: " << record.instrument_descriptor.unit_;
 
  for (const auto &pd : record.point_data_attr_)