Fix issue 9485: knownConditionTrueFalse false positive with integer constants (#2447)

* Fix issue 9485: knownConditionTrueFalse false positive with integer constants

* Formatting

Author: pfultz2

lib/checkother.cpp

@@ -1987,7 +1987,15 @@ void CheckOther::checkDuplicateExpression()
             if (tok->isOp() && tok->astOperand1() && !Token::Match(tok, "+|*|<<|>>|+=|*=|<<=|>>=")) {
                 if (Token::Match(tok, "==|!=|-") && astIsFloat(tok->astOperand1(), true))
                     continue;
-                if (isSameExpression(mTokenizer->isCPP(), true, tok->astOperand1(), tok->astOperand2(), mSettings->library, true, true, &errorPath)) {
+                const bool followVar = !isConstVarExpression(tok) || Token::Match(tok, "%comp%|%oror%|&&");
+                if (isSameExpression(mTokenizer->isCPP(),
+                                     true,
+                                     tok->astOperand1(),
+                                     tok->astOperand2(),
+                                     mSettings->library,
+                                     true,
+                                     followVar,
+                                     &errorPath)) {
                     if (isWithoutSideEffects(mTokenizer->isCPP(), tok->astOperand1())) {
                         const bool assignment = tok->str() == "=";
                         if (assignment && warningEnabled)
@@ -2005,17 +2013,39 @@ void CheckOther::checkDuplicateExpression()
                             duplicateExpressionError(tok->astOperand1(), tok->astOperand2(), tok, errorPath);
                         }
                     }
-                } else if (tok->str() == "=" && Token::simpleMatch(tok->astOperand2(), "=") && isSameExpression(mTokenizer->isCPP(), false, tok->astOperand1(), tok->astOperand2()->astOperand1(), mSettings->library, true, false)) {
+                } else if (tok->str() == "=" && Token::simpleMatch(tok->astOperand2(), "=") &&
+                           isSameExpression(mTokenizer->isCPP(),
+                                            false,
+                                            tok->astOperand1(),
+                                            tok->astOperand2()->astOperand1(),
+                                            mSettings->library,
+                                            true,
+                                            false)) {
                     if (warningEnabled && isWithoutSideEffects(mTokenizer->isCPP(), tok->astOperand1())) {
                         selfAssignmentError(tok, tok->astOperand1()->expressionString());
                     }
                 } else if (styleEnabled &&
-                           isOppositeExpression(mTokenizer->isCPP(), tok->astOperand1(), tok->astOperand2(), mSettings->library, false, true, &errorPath) &&
+                           isOppositeExpression(mTokenizer->isCPP(),
+                                                tok->astOperand1(),
+                                                tok->astOperand2(),
+                                                mSettings->library,
+                                                false,
+                                                true,
+                                                &errorPath) &&
                            !Token::Match(tok, "=|-|-=|/|/=") &&
                            isWithoutSideEffects(mTokenizer->isCPP(), tok->astOperand1())) {
                     oppositeExpressionError(tok, errorPath);
                 } else if (!Token::Match(tok, "[-/%]")) { // These operators are not associative
-                    if (styleEnabled && tok->astOperand2() && tok->str() == tok->astOperand1()->str() && isSameExpression(mTokenizer->isCPP(), true, tok->astOperand2(), tok->astOperand1()->astOperand2(), mSettings->library, true, true, &errorPath) && isWithoutSideEffects(mTokenizer->isCPP(), tok->astOperand2()))
+                    if (styleEnabled && tok->astOperand2() && tok->str() == tok->astOperand1()->str() &&
+                        isSameExpression(mTokenizer->isCPP(),
+                                         true,
+                                         tok->astOperand2(),
+                                         tok->astOperand1()->astOperand2(),
+                                         mSettings->library,
+                                         true,
+                                         followVar,
+                                         &errorPath) &&
+                        isWithoutSideEffects(mTokenizer->isCPP(), tok->astOperand2()))
                         duplicateExpressionError(tok->astOperand2(), tok->astOperand1()->astOperand2(), tok, errorPath);
                     else if (tok->astOperand2() && isConstExpression(tok->astOperand1(), mSettings->library, true, mTokenizer->isCPP())) {
                         const Token *ast1 = tok->astOperand1();

test/testother.cpp

@@ -139,6 +139,7 @@ class TestOther : public TestFixture {
         TEST_CASE(duplicateExpression7);
         TEST_CASE(duplicateExpression8);
         TEST_CASE(duplicateExpression9); // #9320
+        TEST_CASE(duplicateExpression10); // #9485
         TEST_CASE(duplicateExpressionLoop);
         TEST_CASE(duplicateValueTernary);
         TEST_CASE(duplicateExpressionTernary); // #6391
@@ -4657,6 +4658,18 @@ class TestOther : public TestFixture {
         ASSERT_EQUALS("", errout.str());
     }
 
+    void duplicateExpression10()
+    {
+        // #9485
+        check("int f() {\n"
+              "   const int a = 1;\n"
+              "   const int b = a-1;\n"
+              "   const int c = a+1;\n"
+              "   return c;\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+    }
+
     void duplicateExpressionLoop() {
         check("void f() {\n"
               "    int a = 1;\n"