diff --git a/src/Converter.cc b/src/Converter.cc
index 542c14813..451f4b696 100644
--- a/src/Converter.cc
+++ b/src/Converter.cc
@@ -88,7 +88,7 @@ bool Converter::Convert(tinyxml2::XMLDocument *_doc,
     return false;
   }
 
-  if (!elem || !elem->Attribute("version"))
+  if (!elem->Attribute("version"))
   {
     sdferr << "  Unable to determine original SDF version\n";
     return false;
diff --git a/src/FrameSemantics.cc b/src/FrameSemantics.cc
index 94893dcf5..6081aac97 100644
--- a/src/FrameSemantics.cc
+++ b/src/FrameSemantics.cc
@@ -44,7 +44,6 @@ inline namespace SDF_VERSION_NAMESPACE {
 // Helpful functions when debugging in gdb
 void printGraph(const ScopedGraph<PoseRelativeToGraph> &_graph)
 {
-  std::stringstream ss;
   std::cout << _graph.Graph() << std::endl;
 }
 void printGraph(const ScopedGraph<FrameAttachedToGraph> &_graph)
@@ -258,7 +257,7 @@ std::pair<const Link *, std::string>
 /// be modified.
 static Errors resolveModelPoseWithPlacementFrame(
     const ignition::math::Pose3d &_rawPose,
-    const std::string _placementFrame,
+    const std::string &_placementFrame,
     const sdf::ScopedGraph<PoseRelativeToGraph> &_graph,
     ignition::math::Pose3d &_resolvedPose)
 {
diff --git a/src/parser.cc b/src/parser.cc
index 0b11d0f03..699c15fab 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -661,6 +661,7 @@ bool readDoc(tinyxml2::XMLDocument *_xmlDoc, SDFPtr _sdf,
   tinyxml2::XMLElement *sdfNode = _xmlDoc->FirstChildElement("sdf");
   if (!sdfNode)
   {
+    sdfdbg << "No <sdf> element in file[" << _source << "]\n";
     return false;
   }
 
@@ -675,7 +676,7 @@ bool readDoc(tinyxml2::XMLDocument *_xmlDoc, SDFPtr _sdf,
     _sdf->SetFilePath(_source);
   }
 
-  if (sdfNode && sdfNode->Attribute("version"))
+  if (sdfNode->Attribute("version"))
   {
     if (_sdf->OriginalVersion().empty())
     {
@@ -737,15 +738,8 @@ bool readDoc(tinyxml2::XMLDocument *_xmlDoc, SDFPtr _sdf,
   }
   else
   {
-    if (!sdfNode)
-    {
-      sdfdbg << "No <sdf> element in file[" << _source << "]\n";
-    }
-    else if (!sdfNode->Attribute("version"))
-    {
-      sdfdbg << "SDF <sdf> element has no version in file["
-             << _source << "]\n";
-    }
+    sdfdbg << "SDF <sdf> element has no version in file["
+           << _source << "]\n";
     return false;
   }
 
@@ -767,6 +761,7 @@ bool readDoc(tinyxml2::XMLDocument *_xmlDoc, ElementPtr _sdf,
   tinyxml2::XMLElement *sdfNode = _xmlDoc->FirstChildElement("sdf");
   if (!sdfNode)
   {
+    sdfdbg << "SDF has no <sdf> element\n";
     return false;
   }
 
@@ -775,7 +770,7 @@ bool readDoc(tinyxml2::XMLDocument *_xmlDoc, ElementPtr _sdf,
     _sdf->SetFilePath(_source);
   }
 
-  if (sdfNode && sdfNode->Attribute("version"))
+  if (sdfNode->Attribute("version"))
   {
     if (_sdf->OriginalVersion().empty())
     {
@@ -838,14 +833,7 @@ bool readDoc(tinyxml2::XMLDocument *_xmlDoc, ElementPtr _sdf,
   }
   else
   {
-    if (!sdfNode)
-    {
-      sdfdbg << "SDF has no <sdf> element\n";
-    }
-    else if (!sdfNode->Attribute("version"))
-    {
-      sdfdbg << "<sdf> element has no version\n";
-    }
+    sdfdbg << "<sdf> element has no version\n";
     return false;
   }
 
@@ -1149,7 +1137,7 @@ static bool readAttributes(tinyxml2::XMLElement *_xml, ElementPtr _sdf,
 /// \param[out] _errors Captures errors found during parsing.
 /// \return True if the file name is successfully resolved, false on error.
 static bool resolveFileNameFromUri(tinyxml2::XMLElement *_includeXml,
-    const sdf::ParserConfig &_config, const std::string _includeXmlPath,
+    const sdf::ParserConfig &_config, const std::string &_includeXmlPath,
     const std::string &_errorSourcePath, std::string &_fileName,
     Errors &_errors)
 {
diff --git a/src/parser_TEST.cc b/src/parser_TEST.cc
index 29beaee98..017c9cd9e 100644
--- a/src/parser_TEST.cc
+++ b/src/parser_TEST.cc
@@ -581,7 +581,7 @@ TEST_F(ValueConstraintsFixture, ElementMinMaxValues)
   auto sdf = InitSDF();
   sdf->Root()->AddElementDescription(sdfTest->Root());
 
-  auto wrapInSdf = [](std::string _xml) -> std::string
+  auto wrapInSdf = [](const std::string &_xml) -> std::string
   {
     std::stringstream ss;
     ss << "<sdf version=\"" << SDF_PROTOCOL_VERSION << "\"><test>" << _xml
diff --git a/test/integration/interface_api.cc b/test/integration/interface_api.cc
index 6d7bdde83..77180114c 100644
--- a/test/integration/interface_api.cc
+++ b/test/integration/interface_api.cc
@@ -392,7 +392,7 @@ TEST_F(InterfaceAPI, FrameSemantics)
   EXPECT_EQ(1u, world->InterfaceModelCount());
 
   auto resolvePoseNoErrors =
-      [](const sdf::SemanticPose &_semPose, const std::string _relativeTo = "")
+      [](const sdf::SemanticPose &_semPose, const std::string &_relativeTo = "")
   {
     Pose3d pose;
     sdf::Errors resolveErrors = _semPose.Resolve(pose, _relativeTo);
diff --git a/test/integration/nested_model.cc b/test/integration/nested_model.cc
index 904115114..d6056274d 100644
--- a/test/integration/nested_model.cc
+++ b/test/integration/nested_model.cc
@@ -993,7 +993,7 @@ class PlacementFrame: public ::testing::Test
   }
 
   public: sdf::SemanticPose GetChildEntitySemanticPose(
-      const sdf::World *_world, const std::string _entityName)
+      const sdf::World *_world, const std::string &_entityName)
   {
     return _world->ModelByName(_entityName)->SemanticPose();
   }
diff --git a/test/integration/unknown.cc b/test/integration/unknown.cc
index 35ade31b6..7e9b2ed5a 100644
--- a/test/integration/unknown.cc
+++ b/test/integration/unknown.cc
@@ -142,7 +142,7 @@ TEST(UnrecognizedElements, OldElementsInNewSchemas)
 {
   // This should be valid in 1.6, but not in 1.8 (do to usage of
   // `use_parent_model_frame`).
-  auto make_model_xml_string = [](std::string version)
+  auto make_model_xml_string = [](const std::string &version)
   {
     return R"(
 <?xml version="1.0" ?>