Fix #11406 FP returnDanglingLifetime, std::unique_ptr and implicit conversion to bool (#4600)

lib/checkautovariables.cpp

@@ -578,7 +578,8 @@ void CheckAutoVariables::checkVarLifetimeScope(const Token * start, const Token
                 }
             }
         }
-        const bool escape = Token::Match(tok->astParent(), "return|throw");
+        const bool escape = Token::simpleMatch(tok->astParent(), "throw") ||
+                            (Token::simpleMatch(tok->astParent(), "return") && !Function::returnsStandardType(scope->function));
         std::unordered_set<const Token*> exprs;
         for (const ValueFlow::Value& val:tok->values()) {
             if (!val.isLocalLifetimeValue() && !val.isSubFunctionLifetimeValue())

lib/symboldatabase.cpp

@@ -2931,6 +2931,13 @@ bool Function::returnsReference(const Function* function, bool unknown)
     });
 }
 
+bool Function::returnsStandardType(const Function* function, bool unknown)
+{
+    return checkReturns(function, unknown, true, [](UNUSED const Token* defStart, const Token* defEnd) {
+        return defEnd->previous() && defEnd->previous()->isStandardType();
+    });
+}
+
 bool Function::returnsVoid(const Function* function, bool unknown)
 {
     return checkReturns(function, unknown, true, [](UNUSED const Token* defStart, const Token* defEnd) {

lib/symboldatabase.h

@@ -930,6 +930,7 @@ public:
     static bool returnsConst(const Function* function, bool unknown = false);
 
     static bool returnsReference(const Function* function, bool unknown = false);
+    static bool returnsStandardType(const Function* function, bool unknown = false);
 
     static bool returnsVoid(const Function* function, bool unknown = false);
 

test/testautovariables.cpp

@@ -2768,6 +2768,22 @@ private:
         ASSERT_EQUALS(
             "[test.cpp:2] -> [test.cpp:1] -> [test.cpp:3]: (error) Returning pointer to local variable 'p' that will be invalid when returning.\n",
             errout.str());
+
+        check("int* f();\n" // #11406
+              "bool g() {\n"
+              "    std::unique_ptr<int> ptr(f());\n"
+              "    return ptr.get();\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+
+        check("int* f();\n"
+              "int* g() {\n"
+              "    std::unique_ptr<int> ptr(f());\n"
+              "    return ptr.get();\n"
+              "}\n");
+        ASSERT_EQUALS(
+            "[test.cpp:4] -> [test.cpp:3] -> [test.cpp:4]: (error) Returning object that points to local variable 'ptr' that will be invalid when returning.\n",
+            errout.str());
     }
     void danglingLifetime() {
         check("auto f() {\n"