Fix 11980: False positive returnDanglingLifetime returning pointer to stack array as std::string (by way of struct return value constructor) (#5445)

Author: pfultz2

lib/astutils.cpp

@@ -724,7 +724,8 @@ std::vector<ValueType> getParentValueTypes(const Token* tok, const Settings* set
                 const Scope* scope = t->classScope;
                 // Check for aggregate constructors
                 if (scope && scope->numConstructors == 0 && t->derivedFrom.empty() &&
-                    (t->isClassType() || t->isStructType()) && numberOfArguments(ftok) < scope->varlist.size()) {
+                    (t->isClassType() || t->isStructType()) && numberOfArguments(ftok) <= scope->varlist.size() &&
+                    !scope->varlist.empty()) {
                     assert(argn < scope->varlist.size());
                     auto it = std::next(scope->varlist.cbegin(), argn);
                     if (it->valueType())

lib/valueflow.cpp

@@ -4602,7 +4602,7 @@ static void valueFlowLifetimeClassConstructor(Token* tok,
                 const Variable& var = *it;
                 if (var.isReference() || var.isRValueReference()) {
                     ls.byRef(tok, tokenlist, errorLogger, settings);
-                } else {
+                } else if (ValueFlow::isLifetimeBorrowed(ls.argtok, settings)) {
                     ls.byVal(tok, tokenlist, errorLogger, settings);
                 }
                 it++;

test/testautovariables.cpp

@@ -3750,6 +3750,15 @@ class TestAutoVariables : public TestFixture {
               "    return A{y, x};\n"
               "}");
         ASSERT_EQUALS("", errout.str());
+
+        check("struct a {\n"
+              "    std::string m;\n"
+              "};\n"
+              "a f() {\n"
+              "    std::array<char, 1024> m {};\n"
+              "    return { m.data() };\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void danglingLifetimeInitList() {