null pointers: fixed false positives when checking if pointer is null at many locations (#485)

src/checkother.cpp

@@ -1042,6 +1042,21 @@ void CheckOther::nullPointer()
             if (varid1 == 0)
                 continue;
 
+            // Checking if the struct pointer is non-null before the assignment..
+            {
+                const Token *tok2 = _tokenizer->tokens();
+                while (tok2)
+                {
+                    if (tok2 == tok1)
+                        break;
+                    if (Token::Match(tok2, "if|while ( !| %varid% )", varid1))
+                        break;
+                    tok2 = tok2->next();
+                }
+                if (tok2 != tok1)
+                    continue;
+            }
+
             unsigned int indentlevel2 = 0;
             for (const Token *tok2 = tok1->tokAt(3); tok2; tok2 = tok2->next())
             {

test/testother.cpp

@@ -508,6 +508,18 @@ private:
                          "        ;\n"
                          "}\n");
         ASSERT_EQUALS("", errout.str());
+
+        // while..
+        checkNullPointer("void freeAbc(struct ABC *abc)\n"
+                         "{\n"
+                         "    while (abc)\n"
+                         "    {\n"
+                         "        struct ABC *next = abc->next;\n"
+                         "        if (abc) delete abc;\n"
+                         "        abc = next;\n"
+                         "    }\n"
+                         "}\n");
+        ASSERT_EQUALS("", errout.str());
     }
 
     // Dereferencing a pointer and then checking if it is null