Fix #14247 FN returnDanglingLifetime with designated initializer (#7937)

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

Author: chrchr-github

lib/astutils.cpp

@@ -1022,6 +1022,11 @@ const Token* isInLoopCondition(const Token* tok)
     return Token::Match(top->previous(), "for|while (") ? top : nullptr;
 }
 
+bool isDesignatedInitializer(const Token* tok)
+{
+    return tok && tok->isUnaryOp(".");
+}
+
 /// If tok2 comes after tok1
 bool precedes(const Token * tok1, const Token * tok2)
 {

lib/astutils.h

@@ -265,6 +265,11 @@ bool isStructuredBindingVariable(const Variable* var);
 
 const Token* isInLoopCondition(const Token* tok);
 
+/**
+ * Is token the dot of a designated initializer?
+ */
+bool isDesignatedInitializer(const Token* tok);
+
 /**
  * Is token used as boolean, that is to say cast to a bool, or used as a condition in a if/while/for
  */

lib/valueflow.cpp

@@ -2860,6 +2860,7 @@ static void valueFlowLifetimeClassConstructor(Token* tok,
         std::vector<const Token*> args = getArguments(tok);
         if (scope->numConstructors == 0) {
             auto it = scope->varlist.cbegin();
+            const bool hasDesignatedInitializers = !args.empty() && isDesignatedInitializer(args[0]->astOperand1());
             LifetimeStore::forEach(
                 tokenlist,
                 errorLogger,
@@ -2869,20 +2870,25 @@ static void valueFlowLifetimeClassConstructor(Token* tok,
                 ValueFlow::Value::LifetimeKind::SubObject,
                 [&](LifetimeStore& ls) {
                 // Skip static variable
-                it = std::find_if(it, scope->varlist.cend(), [](const Variable& var) {
-                    return !var.isStatic();
+                it = std::find_if(it, scope->varlist.cend(), [&](const Variable &var) {
+                    return !var.isStatic() && (!hasDesignatedInitializers || var.name() == ls.argtok->astOperand1()->astOperand1()->str());
                 });
                 if (it == scope->varlist.cend())
                     return;
-                const Variable& var = *it;
+                if (hasDesignatedInitializers)
+                    ls.argtok = ls.argtok->astOperand2();
+                const Variable &var = *it;
                 if (var.valueType() && var.valueType()->container && var.valueType()->container->stdStringLike && !var.valueType()->container->view)
                     return; // TODO: check in isLifetimeBorrowed()?
                 if (var.isReference() || var.isRValueReference()) {
                     ls.byRef(tok, tokenlist, errorLogger, settings);
                 } else if (ValueFlow::isLifetimeBorrowed(ls.argtok, settings)) {
                     ls.byVal(tok, tokenlist, errorLogger, settings);
                 }
-                it++;
+                if (hasDesignatedInitializers)
+                    it = scope->varlist.cbegin();
+                else
+                    it++;
             });
         } else {
             const Function* constructor = findConstructor(scope, tok, args);

test/testautovariables.cpp

@@ -3937,6 +3937,42 @@ class TestAutoVariables : public TestFixture {
         ASSERT_EQUALS(
             "[test.cpp:6:30] -> [test.cpp:6:30] -> [test.cpp:6:21] -> [test.cpp:5:21] -> [test.cpp:8:12]: (error) Returning object that points to local variable 'a' that will be invalid when returning. [returnDanglingLifetime]\n",
             errout_str());
+
+        check("struct A { int& x; };\n" // #14247
+              "A f() {\n"
+              "    int x = 0;\n"
+              "    A a{.x = x};\n"
+              "    return a;\n"
+              "}\n");
+        ASSERT_EQUALS(
+            "[test.cpp:4:14] -> [test.cpp:3:9] -> [test.cpp:5:12]: (error) Returning object that points to local variable 'x' that will be invalid when returning. [returnDanglingLifetime]\n",
+            errout_str());
+
+        check("struct A { int x; int& r};\n"
+              "A f(int& r) {\n"
+              "    int x = 0;\n"
+              "    A a{.x = x, .r = r};\n"
+              "    return a;\n"
+              "}\n");
+        ASSERT_EQUALS("", errout_str());
+
+        check("struct A { int& x; };\n"
+              "A f() {\n"
+              "    int x = 0;\n"
+              "    A a{ .x{x} };\n"
+              "    return a;\n"
+              "}\n");
+        ASSERT_EQUALS(
+            "[test.cpp:4:13] -> [test.cpp:3:9] -> [test.cpp:5:12]: (error) Returning object that points to local variable 'x' that will be invalid when returning. [returnDanglingLifetime]\n",
+            errout_str());
+
+        check("struct A { int x; int& r};\n"
+              "A f(int& r) {\n"
+              "    int x = 0;\n"
+              "    A a{ .x{x}, .r{r} };\n"
+              "    return a;\n"
+              "}\n");
+        ASSERT_EQUALS("", errout_str());
     }
 
     void danglingLifetimeInitList() {