Fix #10993 danglingTemporaryLifetime reported in two different locati… (#4462)

* Fix #10993 danglingTemporaryLifetime reported in two different locations for std::string_view usage

* Missing include

* Add test

lib/checkautovariables.cpp

@@ -392,6 +392,13 @@ void CheckAutoVariables::errorUselessAssignmentPtrArg(const Token *tok)
                 "Assignment of function parameter has no effect outside the function. Did you forget dereferencing it?", CWE398, Certainty::normal);
 }
 
+bool CheckAutoVariables::diag(const Token* tokvalue)
+{
+    if (!tokvalue)
+        return true;
+    return !mDiagDanglingTemp.insert(tokvalue).second;
+}
+
 //---------------------------------------------------------------------------
 
 static bool isInScope(const Token * tok, const Scope * scope)
@@ -603,7 +610,8 @@ void CheckAutoVariables::checkVarLifetimeScope(const Token * start, const Token
                         break;
                     } else if (!tokvalue->variable() &&
                                isDeadTemporary(mTokenizer->isCPP(), tokvalue, tok, &mSettings->library)) {
-                        errorDanglingTemporaryLifetime(tok, &val, tokvalue);
+                        if (!diag(tokvalue))
+                            errorDanglingTemporaryLifetime(tok, &val, tokvalue);
                         break;
                     }
                 }

lib/checkautovariables.h

@@ -27,6 +27,7 @@
 #include "errortypes.h"
 
 #include <string>
+#include <set>
 
 class Settings;
 class Token;
@@ -127,6 +128,11 @@ private:
                "- suspicious assignment of pointer argument\n"
                "- useless assignment of function argument\n";
     }
+
+    /** returns true if tokvalue has already been diagnosed */
+    bool diag(const Token* tokvalue);
+
+    std::set<const Token*> mDiagDanglingTemp;
 };
 /// @}
 //---------------------------------------------------------------------------

test/testautovariables.cpp

@@ -2744,6 +2744,12 @@ private:
               "    return sv;\n"
               "}\n");
         ASSERT_EQUALS("", errout.str());
+
+        check("void f() {\n" // #10993
+              "    std::string_view v = std::string();\n"
+              "    v.data();\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:2] -> [test.cpp:3]: (error) Using object that is a temporary.\n", errout.str());
     }
 
     void danglingLifetimeUniquePtr()