Fix #14818 FP returnDanglingLifetime when passing c_str() to function (#8750)

Co-authored-by: chrchr-github <noreply@github.com>

Author: chrchr-github

lib/valueflow.cpp

@@ -2542,6 +2542,8 @@ static void valueFlowLifetimeFunction(Token *tok, const TokenList &tokenlist, Er
         for (const Token* returnTok : returns) {
             if (returnTok == tok)
                 continue;
+            if (!ValueFlow::isLifetimeBorrowed(returnTok, settings))
+                return;
             const Variable *returnVar = ValueFlow::getLifetimeVariable(returnTok, settings);
             if (returnVar && returnVar->isArgument() && (returnVar->isConst() || !isVariableChanged(returnVar, settings))) {
                 LifetimeStore ls = LifetimeStore::fromFunctionArg(f, tok, returnVar, tokenlist, settings, errorLogger);

test/testautovariables.cpp

@@ -2962,6 +2962,15 @@ class TestAutoVariables : public TestFixture {
               "    int m;\n"
               "}\n");
         ASSERT_EQUALS("", errout_str());
+
+        check("std::string to_string(const char* p) {\n" // #14818
+              "    return p;\n"
+              "}\n"
+              "std::string get() {\n"
+              "    std::string s;\n"
+              "    return to_string(s.c_str());\n"
+              "}\n");
+        ASSERT_EQUALS("", errout_str());
     }
 
     void danglingLifetimeContainerView()