Fix #10083 FN unusedScopedObject: temporary lock 'std::lock_guard<std::mutex>(m)' (#4522)

* Fix #10083 FN unusedScopedObject: temporary lock 'std::lock_guard<std::mutex>(m)'

* Format

* Fix cppcheck-cfg.rng

* Format

cfg/cppcheck-cfg.rng

@@ -551,6 +551,9 @@
                 <element name="suppress">
                   <ref name="DATA-EXTNAME"/>
                 </element>
+                <element name="checkFiniteLifetime">
+                  <ref name="DATA-EXTNAME"/>
+                </element>
               </choice>
             </zeroOrMore>
           </element>

cfg/std.cfg

@@ -8664,16 +8664,16 @@ initializer list (7) string& replace (const_iterator i1, const_iterator i2, init
   <smart-pointer class-name="std::weak_ptr"/>
   <type-checks>
     <unusedvar>
-      <suppress>std::insert_iterator</suppress>
-      <suppress>std::lock_guard</suppress>
-      <suppress>std::unique_lock</suppress>
-      <suppress>std::shared_lock</suppress>
       <suppress>std::fstream</suppress>
       <suppress>std::wfstream</suppress>
       <suppress>std::ofstream</suppress>
       <suppress>std::wofstream</suppress>
       <suppress>std::basic_fstream</suppress>
       <suppress>std::basic_ofstream</suppress>
+      <checkFiniteLifetime>std::insert_iterator</checkFiniteLifetime>
+      <checkFiniteLifetime>std::lock_guard</checkFiniteLifetime>
+      <checkFiniteLifetime>std::unique_lock</checkFiniteLifetime>
+      <checkFiniteLifetime>std::shared_lock</checkFiniteLifetime>
       <check>std::pair</check>
       <check>std::exception</check>
       <check>std::logic_error</check>

lib/checkother.cpp

@@ -2077,7 +2077,7 @@ void CheckOther::checkMisusedScopedObject()
         const Token* endTok = tok;
         if (Token::Match(endTok, "%name% <"))
             endTok = endTok->linkAt(1);
-        if (Token::Match(endTok, "%name%|> (|{") && Token::Match(endTok->linkAt(1), ")|} ; !!}") &&
+        if (Token::Match(endTok, "%name%|> (|{") && Token::Match(endTok->linkAt(1), ")|} ;") &&
             !Token::simpleMatch(endTok->next()->astParent(), ";")) { // for loop condition
             return tok;
         }
@@ -2085,7 +2085,8 @@ void CheckOther::checkMisusedScopedObject()
     };
 
     auto isLibraryConstructor = [&](const Token* tok, const std::string& typeStr) -> bool {
-        if (mSettings->library.getTypeCheck("unusedvar", typeStr) == Library::TypeCheck::check)
+        const Library::TypeCheck typeCheck = mSettings->library.getTypeCheck("unusedvar", typeStr);
+        if (typeCheck == Library::TypeCheck::check || typeCheck == Library::TypeCheck::checkFiniteLifetime)
             return true;
         return mSettings->library.detectContainerOrIterator(tok);
     };

lib/checkunusedvar.cpp

@@ -1268,6 +1268,7 @@ void CheckUnusedVar::checkFunctionVariableUsage()
                     case Library::TypeCheck::check:
                         break;
                     case Library::TypeCheck::suppress:
+                    case Library::TypeCheck::checkFiniteLifetime:
                         continue;
                     }
                 }
@@ -1365,6 +1366,7 @@ void CheckUnusedVar::checkFunctionVariableUsage()
                         case Library::TypeCheck::check:
                             break;
                         case Library::TypeCheck::suppress:
+                        case Library::TypeCheck::checkFiniteLifetime:
                             error = false;
                         }
                     }

lib/library.cpp

@@ -553,6 +553,8 @@ Library::Error Library::load(const tinyxml2::XMLDocument &doc)
                         mTypeChecks[std::pair<std::string,std::string>(checkName, typeName)] = TypeCheck::check;
                     else if (checkTypeName == "suppress")
                         mTypeChecks[std::pair<std::string,std::string>(checkName, typeName)] = TypeCheck::suppress;
+                    else if (checkTypeName == "checkFiniteLifetime")
+                        mTypeChecks[std::pair<std::string,std::string>(checkName, typeName)] = TypeCheck::checkFiniteLifetime;
                 }
             }
         }

lib/library.h

@@ -554,7 +554,11 @@ public:
     static bool isContainerYield(const Token * const cond, Library::Container::Yield y, const std::string& fallback=emptyString);
 
     /** Suppress/check a type */
-    enum class TypeCheck { def, check, suppress };
+    enum class TypeCheck { def,
+                           check,
+                           suppress,
+                           checkFiniteLifetime, // (unusedvar) object has side effects, but immediate destruction is wrong
+    };
     TypeCheck getTypeCheck(std::string check, std::string typeName) const;
 
 private:

test/testother.cpp

@@ -138,7 +138,6 @@ private:
         TEST_CASE(testMisusedScopeObjectDoesNotPickPureC);
         TEST_CASE(testMisusedScopeObjectDoesNotPickNestedClass);
         TEST_CASE(testMisusedScopeObjectInConstructor);
-        TEST_CASE(testMisusedScopeObjectNoCodeAfter);
         TEST_CASE(testMisusedScopeObjectStandardType);
         TEST_CASE(testMisusedScopeObjectNamespace);
         TEST_CASE(trac2071);
@@ -5044,14 +5043,6 @@ private:
         ASSERT_EQUALS("[test.cpp:4]: (style) Instance of 'Foo' object is destroyed immediately.\n", errout.str());
     }
 
-    void testMisusedScopeObjectNoCodeAfter() {
-        check("class Foo {};\n"
-              "void f() {\n"
-              "  Foo();\n" // No code after class => don't warn
-              "}", "test.cpp");
-        ASSERT_EQUALS("", errout.str());
-    }
-
     void testMisusedScopeObjectStandardType() {
         check("int g();\n"
               "void f(int i) {\n"
@@ -5111,6 +5102,15 @@ private:
                       "[test.cpp:3]: (style) Instance of 'std::string' object is destroyed immediately.\n"
                       "[test.cpp:4]: (style) Instance of 'std::pair' object is destroyed immediately.\n",
                       errout.str());
+
+        check("struct S {\n" // #10083
+              "    void f() {\n"
+              "        std::lock_guard<std::mutex>(m);\n"
+              "    }\n"
+              "    std::mutex m;\n"
+              "}\n", "test.cpp");
+        ASSERT_EQUALS("[test.cpp:3]: (style) Instance of 'std::lock_guard' object is destroyed immediately.\n",
+                      errout.str());
     }
 
     void trac2084() {