Fix 13114: FN: danglingTempReference (Accessing Temporary Object Through Method Returning Self) (#7409)

Author: pfultz2

lib/valueflow.cpp

@@ -1712,10 +1712,8 @@ static std::vector<ValueFlow::LifetimeToken> getLifetimeTokens(const Token* tok,
                 for (ValueFlow::LifetimeToken& lt : getLifetimeTokens(returnTok, escape, errorPath, pred, settings, depth - returns.size())) {
                     const Token* argvarTok = lt.token;
                     const Variable* argvar = argvarTok->variable();
-                    if (!argvar)
-                        continue;
                     const Token* argTok = nullptr;
-                    if (argvar->isArgument() && (argvar->isReference() || argvar->isRValueReference())) {
+                    if (argvar && argvar->isArgument() && (argvar->isReference() || argvar->isRValueReference())) {
                         const int n = getArgumentPos(argvar, f);
                         if (n < 0)
                             return std::vector<ValueFlow::LifetimeToken> {};

test/testautovariables.cpp

@@ -4356,6 +4356,35 @@ class TestAutoVariables : public TestFixture {
               "    *p = ret;\n"
               "}\n");
         ASSERT_EQUALS("", errout_str());
+
+        check("struct A {\n"
+              "    int val=42;\n"
+              "    const A& Get() const & {\n"
+              "        return *this;\n"
+              "    }\n"
+              "};\n"
+              "const A *ptr;\n"
+              "int main() {\n"
+              "    ptr = &A().Get();\n"
+              "    return ptr->val;\n"
+              "}\n");
+        ASSERT_EQUALS(
+            "[test.cpp:4] -> [test.cpp:9] -> [test.cpp:9] -> [test.cpp:9] -> [test.cpp:10]: (error) Using pointer that is a temporary.\n",
+            errout_str());
+
+        check("struct A {\n"
+              "    int val = 42;\n"
+              "    const A& Get() const {\n"
+              "        return *this;\n"
+              "    }\n"
+              "};\n"
+              "int main() {\n"
+              "    const A& r = A().Get();\n"
+              "    return r.val;\n"
+              "}\n");
+        ASSERT_EQUALS(
+            "[test.cpp:8] -> [test.cpp:4] -> [test.cpp:8] -> [test.cpp:9]: (error) Using reference to dangling temporary.\n",
+            errout_str());
     }
 
     void invalidLifetime() {