Fixed #599 (False positive: null pointer dereference)

src/checkother.cpp

@@ -1159,7 +1159,7 @@ void CheckOther::nullPointer()
 
                 else if (Token::Match(tok2, "if ( !| %varid% )", varid1))
                 {
-                    nullPointerError(tok1, varname);
+                    nullPointerError(tok1, varname, tok2->linenr());
                     break;
                 }
             }
@@ -1344,6 +1344,13 @@ void CheckOther::nullPointerError(const Token *tok, const std::string &varname)
     reportError(tok, Severity::error, "nullPointer", "Possible null pointer dereference: " + varname);
 }
 
+void CheckOther::nullPointerError(const Token *tok, const std::string &varname, const int line)
+{
+    std::ostringstream ostr;
+    ostr << line;
+    reportError(tok, Severity::error, "nullPointer", "Possible null pointer dereference: " + varname + " - otherwise it is redundant to check if " + varname + " is null at line " + ostr.str());
+}
+
 void CheckOther::zerodivError(const Token *tok)
 {
     reportError(tok, Severity::error, "zerodiv", "Division by zero");

src/checkother.h

@@ -143,6 +143,7 @@ public:
     void conditionAlwaysTrueFalse(const Token *tok, const std::string &truefalse);
     void strPlusChar(const Token *tok);
     void nullPointerError(const Token *tok, const std::string &varname);
+    void nullPointerError(const Token *tok, const std::string &varname, const int line);
     void zerodivError(const Token *tok);
     void postIncrementError(const Token *tok, const std::string &var_name, const bool isIncrement);
 

test/testother.cpp

@@ -492,7 +492,7 @@ private:
                          "    if (!abc)\n"
                          "        ;\n"
                          "}\n");
-        ASSERT_EQUALS("[test.cpp:3]: (error) Possible null pointer dereference: abc\n", errout.str());
+        ASSERT_EQUALS("[test.cpp:3]: (error) Possible null pointer dereference: abc - otherwise it is redundant to check if abc is null at line 4\n", errout.str());
 
         // ok dereferencing in a condition
         checkNullPointer("void foo(struct ABC *abc)\n"