Fix FP issue 8801: Condition 'a+b' is always true (#1444)

lib/checkcondition.cpp

@@ -1235,6 +1235,25 @@ void CheckCondition::clarifyConditionError(const Token *tok, bool assign, bool b
                 errmsg, CWE398, false);
 }
 
+static bool isConstVarExpression(const Token * tok)
+{
+    if(!tok)
+        return false;
+    if(Token::Match(tok, "%cop%")) {
+        if(tok->astOperand1() && !isConstVarExpression(tok->astOperand1()))
+            return false;
+        if(tok->astOperand2() && !isConstVarExpression(tok->astOperand2()))
+            return false;
+        return true;
+    }
+    if(Token::Match(tok, "%bool%|%num%|%str%|%char%|nullptr|NULL"))
+        return true;
+    if(tok->isEnumerator())
+        return true;
+    if(tok->variable())
+        return tok->variable()->isConst();
+    return false;
+}
 
 void CheckCondition::alwaysTrueFalse()
 {
@@ -1269,7 +1288,7 @@ void CheckCondition::alwaysTrueFalse()
             if (!(constIfWhileExpression || constValExpr || compExpr || returnStatement))
                 continue;
 
-            if (returnStatement && (tok->isEnumerator() || Token::Match(tok, "nullptr|NULL")))
+            if (returnStatement && isConstVarExpression(tok))
                 continue;
 
             if (returnStatement && Token::simpleMatch(tok->astParent(), "return") && tok->variable() && (

test/testcondition.cpp

@@ -2603,6 +2603,13 @@ private:
               "}\n");
         ASSERT_EQUALS("", errout.str());
 
+        check("int f() {\n"
+              "    const int a = 50;\n"
+              "    const int b = 52;\n"
+              "    return a+b;\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+
         check("bool& g();\n"
               "bool f() {\n"
               "    bool & b = g();\n"