Fix #8433 FN unused variable not detected when there is lambda (#5060)

* Fix #8433 FN unused variable not detected when there is lambda

* Format

* Fix tests

* Check lambda return

* Add test

* Undo, add test

* simpleMatch()

* Rename test

lib/checkmemoryleak.cpp

@@ -720,8 +720,6 @@ void CheckMemoryLeakStructMember::check()
             continue;
         if (var->typeEndToken()->isStandardType())
             continue;
-        if (var->scope()->hasInlineOrLambdaFunction())
-            continue;
         checkStructVariable(var);
     }
 }
@@ -921,7 +919,7 @@ void CheckMemoryLeakStructMember::checkStructVariable(const Variable * const var
                 }
 
                 // Returning from function..
-                else if (tok3->str() == "return") {
+                else if ((tok3->scope()->type != Scope::ScopeType::eLambda || tok3->scope() == variable->scope()) && tok3->str() == "return") {
                     // Returning from function without deallocating struct member?
                     if (!Token::Match(tok3, "return %varid% ;", structid) &&
                         !Token::Match(tok3, "return & %varid%", structid) &&

lib/symboldatabase.cpp

@@ -5149,6 +5149,15 @@ const Type* SymbolDatabase::findVariableType(const Scope *start, const Token *ty
     return nullptr;
 }
 
+static bool hasEmptyCaptureList(const Token* tok) {
+    if (!Token::simpleMatch(tok, "{"))
+        return false;
+    const Token* listTok = tok->astParent();
+    if (Token::simpleMatch(listTok, "("))
+        listTok = listTok->astParent();
+    return Token::simpleMatch(listTok, "[ ]");
+}
+
 bool Scope::hasInlineOrLambdaFunction() const
 {
     return std::any_of(nestedList.begin(), nestedList.end(), [&](const Scope* s) {
@@ -5156,7 +5165,7 @@ bool Scope::hasInlineOrLambdaFunction() const
         if (s->type == Scope::eUnconditional && Token::simpleMatch(s->bodyStart->previous(), ") {"))
             return true;
         // Lambda function
-        if (s->type == Scope::eLambda)
+        if (s->type == Scope::eLambda && !hasEmptyCaptureList(s->bodyStart))
             return true;
         if (s->hasInlineOrLambdaFunction())
             return true;

test/testleakautovar.cpp

@@ -2131,15 +2131,13 @@ private:
               "    FILE*f=fopen(fname,a);\n"
               "    std::shared_ptr<FILE> fp{f, [](FILE* x) { free(f); }};\n"
               "}", true);
-        TODO_ASSERT_EQUALS(
+        ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:3]: (error) Mismatching allocation and deallocation: f\n", errout.str());
-            "[test.cpp:2] -> [test.cpp:3]: (error) Mismatching allocation and deallocation: f\n", "", errout.str());
 
         check("void f() {\n"
               "    FILE*f=fopen(fname,a);\n"
               "    std::shared_ptr<FILE> fp{f, [](FILE* x) {}};\n"
               "}", true);
-        TODO_ASSERT_EQUALS(
+        ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:3]: (error) Mismatching allocation and deallocation: f\n", errout.str());
-            "[test.cpp:2] -> [test.cpp:3]: (error) Mismatching allocation and deallocation: f\n", "", errout.str());
 
         check("class C;\n"
               "void f() {\n"

test/testmemleak.cpp

@@ -1737,7 +1737,7 @@ private:
 
         TEST_CASE(customAllocation);
 
-        TEST_CASE(lambdaInForLoop); // #9793
+        TEST_CASE(lambdaInScope); // #9793
     }
 
     void err() {
@@ -2228,8 +2228,8 @@ private:
         ASSERT_EQUALS("[test.c:7]: (error) Memory leak: abc.a\n", errout.str());
     }
 
-    void lambdaInForLoop() { // #9793
+    void lambdaInScope() {
-        check(
+        check( // #9793
             "struct S { int * p{nullptr}; };\n"
             "int main()\n"
             "{\n"
@@ -2242,6 +2242,35 @@ private:
             "    return 0;\n"
             "}", true);
         ASSERT_EQUALS("", errout.str());
+
+        check(
+            "struct S { int* p; };\n"
+            "void f() {\n"
+            "    auto g = []() {\n"
+            "      S s;\n"
+            "      s.p = new int;\n"
+            "    };\n"
+            "}\n", true);
+        ASSERT_EQUALS("[test.cpp:6]: (error) Memory leak: s.p\n", errout.str());
+
+        check(
+            "struct S { int* p; };\n"
+            "void f() {\n"
+            "    S s;\n"
+            "    s.p = new int;\n"
+            "    auto g = [&]() {\n"
+            "        delete s.p;\n"
+            "    };\n"
+            "    g();\n"
+            "}\n"
+            "void h() {\n"
+            "    S s;\n"
+            "    s.p = new int;\n"
+            "    [&]() {\n"
+            "        delete s.p;\n"
+            "    }();\n"
+            "}\n", true);
+        ASSERT_EQUALS("", errout.str());
     }
 };
 

test/testunusedvar.cpp

@@ -6328,6 +6328,13 @@ private:
                               "    });\n"
                               "}");
         ASSERT_EQUALS("", errout.str());
+
+        functionVariableUsage("int f() {\n" // #8433
+                              "    float a;\n"
+                              "    auto lambda = []() {};\n"
+                              "    return 0;\n"
+                              "}\n");
+        ASSERT_EQUALS("[test.cpp:2]: (style) Unused variable: a\n", errout.str());
     }