Fix #10682 Unused QString / #10686 unused std::array / #10005 unused variable with c++11 braced initializer not detected (#3684)

gui/projectfile.cpp

@@ -1035,7 +1035,6 @@ bool ProjectFile::write(const QString &filename)
         for (const QString &tag: tags) {
             xmlWriter.writeStartElement(CppcheckXml::TagWarningsElementName);
             xmlWriter.writeAttribute(CppcheckXml::TagAttributeName, tag);
-            QStringList warnings;
             for (const auto& wt: mWarningTags) {
                 if (wt.second == tag) {
                     xmlWriter.writeStartElement(CppcheckXml::WarningElementName);

lib/checkunusedvar.cpp

@@ -709,6 +709,7 @@ void CheckUnusedVar::checkFunctionVariableUsage_iterateScopes(const Scope* const
             else if (mTokenizer->isC() ||
                      i->typeEndToken()->isStandardType() ||
                      isRecordTypeWithoutSideEffects(i->type()) ||
+                     mSettings->library.detectContainer(i->typeStartToken(), /*iterator*/ false) ||
                      (i->isStlType() &&
                       !Token::Match(i->typeStartToken()->tokAt(2), "lock_guard|unique_lock|shared_ptr|unique_ptr|auto_ptr|shared_lock")))
                 type = Variables::standard;
@@ -728,7 +729,8 @@ void CheckUnusedVar::checkFunctionVariableUsage_iterateScopes(const Scope* const
                     break;
                 }
             }
-            if (i->isArray() && i->isClass()) // Array of class/struct members. Initialized by ctor.
+            if (i->isArray() && i->isClass() && // Array of class/struct members. Initialized by ctor except for std::array
+                !(i->isStlType() && i->valueType() && i->valueType()->containerTypeToken && i->valueType()->containerTypeToken->isStandardType()))
                 variables.write(i->declarationId(), i->nameToken());
             if (i->isArray() && Token::Match(i->nameToken(), "%name% [ %var% ]")) // Array index variable read.
                 variables.read(i->nameToken()->tokAt(2)->varId(), i->nameToken());
@@ -1176,7 +1178,7 @@ void CheckUnusedVar::checkFunctionVariableUsage()
             }
             // not assignment/initialization/increment => continue
             const bool isAssignment = tok->isAssignmentOp() && tok->astOperand1();
-            const bool isInitialization = (Token::Match(tok, "%var% (") && tok->variable() && tok->variable()->nameToken() == tok);
+            const bool isInitialization = (Token::Match(tok, "%var% (|{") && tok->variable() && tok->variable()->nameToken() == tok);
             const bool isIncrementOrDecrement = (tok->tokType() == Token::Type::eIncDecOp);
             if (!isAssignment && !isInitialization && !isIncrementOrDecrement)
                 continue;

test/cfg/qt.cpp

@@ -49,6 +49,12 @@ QString::iterator QString3()
     return it;
 }
 
+void QString4()
+{
+    // cppcheck-suppress unusedVariable
+    QString qs;
+}
+
 void QByteArray1(QByteArray byteArrayArg)
 {
     for (int i = 0; i <= byteArrayArg.size(); ++i) {
@@ -136,6 +142,7 @@ QList<int>::iterator QList3()
 
 void QLinkedList1()
 {
+    // cppcheck-suppress unreadVariable
     QLinkedList<QString> qstringLinkedList1{"one", "two"};
 
     QLinkedList<QString> qstringLinkedList2 = {"one", "two"};

test/testunusedvar.cpp

@@ -5230,6 +5230,16 @@ private:
                               "    return s;\n"
                               "}");
         ASSERT_EQUALS("", errout.str());
+
+        functionVariableUsage("void f() {\n"
+                              "    std::string s(\"foo\");\n"
+                              "}");
+        ASSERT_EQUALS("[test.cpp:2]: (style) Variable 's' is assigned a value that is never used.\n", errout.str());
+
+        functionVariableUsage("void f() {\n"
+                              "    std::string s{ \"foo\" };\n"
+                              "}");
+        ASSERT_EQUALS("[test.cpp:2]: (style) Variable 's' is assigned a value that is never used.\n", errout.str());
     }
 
     void localvarstring2() { // ticket #2929
@@ -5627,6 +5637,11 @@ private:
                               "  std::array<int, ArraySize> X; X.dostuff();\n"
                               "}");
         ASSERT_EQUALS("", errout.str());
+
+        functionVariableUsage("void f() {\n" // #10686
+                              "    std::array<int, 1> a;\n"
+                              "}\n");
+        ASSERT_EQUALS("[test.cpp:2]: (style) Unused variable: a\n", errout.str());
     }
 
     void localvarFuncPtr() {