Replace push_back with emplace_back to avoid unnecessary temporary construction and slightly improve performance.

Author: rajanyadav0307

src/aws-cpp-sdk-core/source/client/ClientConfiguration.cpp

@@ -196,8 +196,9 @@ Aws::Vector<Aws::String> calculateAuthPreferences() {
   Aws::Vector<Aws::String> res;
   auto prefs = Aws::Environment::GetEnv("AWS_AUTH_SCHEME_PREFERENCE");
   Aws::Vector<Aws::String> prefsList  = Aws::Utils::StringUtils::Split(prefs, ',');
+  res.reserve(prefsList.size());  // avoid repeated allocations
   for (auto& pref : prefsList) {
-    res.push_back(Aws::Utils::StringUtils::Trim(pref.c_str()));
+    res.emplace_back(Aws::Utils::StringUtils::Trim(pref.c_str()));
   }
   return res;
 }

src/aws-cpp-sdk-text-to-speech/source/text-to-speech/TextToSpeechManager.cpp

@@ -93,8 +93,7 @@ namespace Aws
                 for (auto& deviceInfo : driver->EnumerateDevices())
                 {
                     AWS_LOGSTREAM_DEBUG(CLASS_TAG, "Adding device " << deviceInfo.deviceName << " for driver " << driver->GetName());
-                    OutputDevicePair device(deviceInfo, driver);
-                    deviceDriverList.push_back(device);
+                    deviceDriverList.emplace_back(deviceInfo, driver);
                 }
             }
 
@@ -120,9 +119,11 @@ namespace Aws
             auto voicesOutcome = m_pollyClient->DescribeVoices(describeVoices);
             if (voicesOutcome.IsSuccess())
             {
-                for (auto& voice : voicesOutcome.GetResult().GetVoices())
+                auto& voices = voicesOutcome.GetResult().GetVoices();
+                m_voices.reserve(voices.size());
+                for (const auto& voice : voices)
                 {
-                    m_voices.push_back(std::pair<Aws::String, Aws::String>(voice.GetName(), voice.GetLanguageName()));
+                    m_voices.emplace_back(voice.GetName(), voice.GetLanguageName());
                 }
             }
             else