diff --git a/clang/include/clang/StaticAnalyzer/Checkers/SValExplainer.h b/clang/include/clang/StaticAnalyzer/Checkers/SValExplainer.h
--- a/clang/include/clang/StaticAnalyzer/Checkers/SValExplainer.h
+++ b/clang/include/clang/StaticAnalyzer/Checkers/SValExplainer.h
@@ -32,7 +32,7 @@
     std::string Str;
     llvm::raw_string_ostream OS(Str);
     S->printPretty(OS, nullptr, PrintingPolicy(ACtx.getLangOpts()));
-    return OS.str();
+    return Str;
   }
 
   bool isThisObject(const SymbolicRegion *R) {
@@ -69,7 +69,7 @@
     std::string Str;
     llvm::raw_string_ostream OS(Str);
     OS << "concrete memory address '" << I << "'";
-    return OS.str();
+    return Str;
   }
 
   std::string VisitNonLocSymbolVal(nonloc::SymbolVal V) {
@@ -82,7 +82,7 @@
     llvm::raw_string_ostream OS(Str);
     OS << (I.isSigned() ? "signed " : "unsigned ") << I.getBitWidth()
        << "-bit integer '" << I << "'";
-    return OS.str();
+    return Str;
   }
 
   std::string VisitNonLocLazyCompoundVal(nonloc::LazyCompoundVal V) {
@@ -123,7 +123,7 @@
     OS << "(" << Visit(S->getLHS()) << ") "
        << std::string(BinaryOperator::getOpcodeStr(S->getOpcode())) << " "
        << S->getRHS();
-    return OS.str();
+    return Str;
   }
 
   // TODO: IntSymExpr doesn't appear in practice.
@@ -177,7 +177,7 @@
     else
       OS << "'" << Visit(R->getIndex()) << "'";
     OS << " of " + Visit(R->getSuperRegion());
-    return OS.str();
+    return Str;
   }
 
   std::string VisitNonParamVarRegion(const NonParamVarRegion *R) {
diff --git a/clang/lib/Analysis/AnalysisDeclContext.cpp b/clang/lib/Analysis/AnalysisDeclContext.cpp
--- a/clang/lib/Analysis/AnalysisDeclContext.cpp
+++ b/clang/lib/Analysis/AnalysisDeclContext.cpp
@@ -387,7 +387,7 @@
     OS << ' ' << OMD->getSelector().getAsString() << ']';
   }
 
-  return OS.str();
+  return Str;
 }
 
 LocationContextManager &AnalysisDeclContext::getLocationContextManager() {
diff --git a/clang/lib/StaticAnalyzer/Checkers/FuchsiaHandleChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/FuchsiaHandleChecker.cpp
--- a/clang/lib/StaticAnalyzer/Checkers/FuchsiaHandleChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/FuchsiaHandleChecker.cpp
@@ -389,7 +389,7 @@
         llvm::raw_string_ostream OS(SBuf);
         OS << "Function '" << FuncDecl->getDeclName()
            << "' returns an open handle";
-        return OS.str();
+        return SBuf;
       } else
         return "";
     });
@@ -405,7 +405,7 @@
         llvm::raw_string_ostream OS(SBuf);
         OS << "Function '" << FuncDecl->getDeclName()
            << "' returns an unowned handle";
-        return OS.str();
+        return SBuf;
       } else
         return "";
     });
@@ -439,7 +439,7 @@
               llvm::raw_string_ostream OS(SBuf);
               OS << "Handle released through " << ParamDiagIdx
                  << llvm::getOrdinalSuffix(ParamDiagIdx) << " parameter";
-              return OS.str();
+              return SBuf;
             } else
               return "";
           });
@@ -453,7 +453,7 @@
             llvm::raw_string_ostream OS(SBuf);
             OS << "Handle allocated through " << ParamDiagIdx
                << llvm::getOrdinalSuffix(ParamDiagIdx) << " parameter";
-            return OS.str();
+            return SBuf;
           } else
             return "";
         });
@@ -467,7 +467,7 @@
             llvm::raw_string_ostream OS(SBuf);
             OS << "Unowned handle allocated through " << ParamDiagIdx
                << llvm::getOrdinalSuffix(ParamDiagIdx) << " parameter";
-            return OS.str();
+            return SBuf;
           } else
             return "";
         });
diff --git a/clang/lib/StaticAnalyzer/Core/HTMLDiagnostics.cpp b/clang/lib/StaticAnalyzer/Core/HTMLDiagnostics.cpp
--- a/clang/lib/StaticAnalyzer/Core/HTMLDiagnostics.cpp
+++ b/clang/lib/StaticAnalyzer/Core/HTMLDiagnostics.cpp
@@ -437,7 +437,7 @@
   for (auto BI : *Buf)
     os << BI;
 
-  return os.str();
+  return file;
 }
 
 void HTMLDiagnostics::dumpCoverageData(
@@ -534,7 +534,7 @@
 </form>
 )<<<";
 
-  return os.str();
+  return s;
 }
 
 void HTMLDiagnostics::FinalizeHTML(const PathDiagnostic& D, Rewriter &R,
@@ -1202,7 +1202,7 @@
   std::string Result;
   llvm::raw_string_ostream OS(Result);
   OS << "<span id=\"" << ClassName << Index << "\">";
-  return OS.str();
+  return Result;
 }
 
 std::string getSpanBeginForControlStart(unsigned Index) {
diff --git a/clang/lib/StaticAnalyzer/Core/MemRegion.cpp b/clang/lib/StaticAnalyzer/Core/MemRegion.cpp
--- a/clang/lib/StaticAnalyzer/Core/MemRegion.cpp
+++ b/clang/lib/StaticAnalyzer/Core/MemRegion.cpp
@@ -444,7 +444,7 @@
   std::string s;
   llvm::raw_string_ostream os(s);
   dumpToStream(os);
-  return os.str();
+  return s;
 }
 
 void MemRegion::dumpToStream(raw_ostream &os) const {