Fix #13360 FN comparisonError with bit mask (regression) (#7051)

Author: chrchr-github

lib/checkcondition.cpp

@@ -368,13 +368,13 @@ void CheckCondition::comparison()
         const Token *expr2 = tok->astOperand2();
         if (!expr1 || !expr2)
             continue;
-        if (expr1->isNumber())
+        if (expr1->hasKnownIntValue())
             std::swap(expr1,expr2);
-        if (!expr2->isNumber())
+        if (!expr2->hasKnownIntValue())
             continue;
         if (!compareTokenFlags(expr1, expr2, /*macro*/ true))
             continue;
-        const MathLib::bigint num2 = MathLib::toBigNumber(expr2->str());
+        const MathLib::bigint num2 = expr2->getKnownIntValue();
         if (num2 < 0)
             continue;
         if (!Token::Match(expr1,"[&|]"))

test/testcondition.cpp

@@ -503,6 +503,15 @@ class TestCondition : public TestFixture {
                "    if (MACRO_ALL == 0) {}\n"
                "}\n");
         ASSERT_EQUALS("", errout_str());
+
+        checkP("void f(int i, int j) {\n" // #13360
+               "    int X = 0x10;\n"
+               "    if ((i & 0xff00) == X) {}\n"
+               "    if (X == (j & 0xff00)) {}\n"
+               "}\n");
+        ASSERT_EQUALS("[test.cpp:3]: (style) Expression '(X & 0xff00) == 0x10' is always false.\n"
+                      "[test.cpp:4]: (style) Expression '(X & 0xff00) == 0x10' is always false.\n",
+                      errout_str());
     }
 
 #define checkPureFunction(code) checkPureFunction_(code, __FILE__, __LINE__)