Fixed #2908 (common logic when using bitwise and)

lib/checkassignif.cpp

@@ -132,3 +132,63 @@ void CheckAssignIf::comparisonError(const Token *tok, bool result)
 
     reportError(tok, Severity::style, "comparisonError", errmsg);
 }
+
+
+
+
+
+
+void CheckAssignIf::multicompare()
+{
+    if (!_settings->_checkCodingStyle)
+        return;
+
+    for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next())
+    {
+        if (Token::Match(tok, "if ( %var% & %num% ) {"))
+        {
+            const unsigned int varid(tok->tokAt(2)->varId());
+            if (varid == 0)
+                continue;
+
+            const MathLib::bigint num1 = MathLib::toLongNumber(tok->strAt(4));
+            if (num1 < 0)
+                continue;
+
+            const Token *tok2 = tok->tokAt(6)->link();
+            while (Token::simpleMatch(tok2, "} else { if ("))
+            {
+                // Goto '('
+                const Token * const opar = tok2->tokAt(4);
+
+                // tok2: skip if-block
+                tok2 = opar->link();
+                if (Token::simpleMatch(tok2, ") {"))
+                    tok2 = tok2->next()->link();
+
+                // check condition..
+                if (Token::Match(opar, "( %varid% == %num% &&|%oror%|)", varid))
+                {
+                    const MathLib::bigint num2 = MathLib::toLongNumber(opar->strAt(3));
+                    if (num2 < 0)
+                        continue;
+
+                    if ((num1 & num2) == num2)
+                    {
+                        multicompareError(opar, tok->linenr());
+                    }
+                }
+            }
+        }
+    }
+}
+
+void CheckAssignIf::multicompareError(const Token *tok, unsigned int line1)
+{
+    std::ostringstream errmsg;
+    errmsg << "Comparison is always false because otherwise the condition at line "
+           << line1
+           << " is not false";
+
+    reportError(tok, Severity::style, "multicompare", errmsg.str());
+}

lib/checkassignif.h

@@ -52,6 +52,7 @@ public:
         CheckAssignIf checkAssignIf(tokenizer, settings, errorLogger);
         checkAssignIf.assignIf();
         checkAssignIf.comparison();
+        checkAssignIf.multicompare();
     }
 
     /** mismatching assignment / comparison */
@@ -60,17 +61,21 @@ public:
     /** mismatching lhs and rhs in comparison */
     void comparison();
 
+    /** match 'if' and 'else if' conditions */
+    void multicompare();
+
 private:
 
     void assignIfError(const Token *tok, bool result);
-
     void comparisonError(const Token *tok, bool result);
+    void multicompareError(const Token *tok, unsigned int line1);
 
     void getErrorMessages(ErrorLogger *errorLogger, const Settings *settings)
     {
         CheckAssignIf c(0, settings, errorLogger);
         c.assignIfError(0, false);
         c.comparisonError(0, false);
+        c.multicompareError(0,1);
     }
 
     std::string myName() const
@@ -82,7 +87,8 @@ private:
     {
         return "Match assignments and conditions:\n"
                " * Mismatching assignment and comparison => comparison is always true/false\n"
-               " * Mismatching lhs and rhs in comparison => comparison is always true/false";
+               " * Mismatching lhs and rhs in comparison => comparison is always true/false\n"
+               " * Match 'if' and 'else if' conditions";
     }
 };
 /// @}

test/testassignif.cpp

@@ -35,8 +35,9 @@ private:
 
     void run()
     {
-        TEST_CASE(assignAndCompare);
-        TEST_CASE(compare);
+        TEST_CASE(assignAndCompare);   // assignment and comparison don't match
+        TEST_CASE(compare);            // mismatching LHS/RHS in comparison
+        TEST_CASE(multicompare);       // mismatching comparisons
     }
 
     void check(const char code[])
@@ -58,6 +59,7 @@ private:
         CheckAssignIf checkAssignIf(&tokenizer, &settings, this);
         checkAssignIf.assignIf();
         checkAssignIf.comparison();
+        checkAssignIf.multicompare();
     }
 
     void assignAndCompare()
@@ -97,6 +99,17 @@ private:
               "}\n");
         ASSERT_EQUALS("[test.cpp:3]: (style) Mismatching comparison, the result is always true\n", errout.str());
     }
+
+    void multicompare()
+    {
+        check("void foo(int x)\n"
+              "{\n"
+              "    if (x & 7);\n"
+              "    else if (x == 1);\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:4]: (style) Comparison is always false because otherwise the condition at line 3 is not false\n", errout.str());
+
+    }
 };
 
 REGISTER_TEST(TestAssignIf)