Null pointer: remove old checking that is replaced by value flow checking
This commit is contained in:
Daniel Marjamäki
parent
20b73747e0
commit
a84fdf98cc
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@ -557,198 +557,6 @@ void CheckNullPointer::nullPointerLinkedList()
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}
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}
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void CheckNullPointer::nullPointerStructByDeRefAndChec()
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{
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// Dereferencing a struct pointer and then checking if it's NULL..
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const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
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// skipvar: don't check vars that has been tested against null already
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std::set<unsigned int> skipvar;
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skipvar.insert(0);
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const std::size_t functions = symbolDatabase->functionScopes.size();
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for (std::size_t i = 0; i < functions; ++i) {
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const Scope * scope = symbolDatabase->functionScopes[i];
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if (scope->function == 0 || !scope->function->hasBody) // We only look for functions with a body
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continue;
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for (const Token *tok1 = scope->classStart; tok1 != scope->classEnd; tok1 = tok1->next()) {
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// Checking if some pointer is null.
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// then add the pointer to skipvar => is it known that it isn't NULL
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if (Token::Match(tok1, "if|while ( !| %var% )")) {
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tok1 = tok1->tokAt(2);
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if (tok1->str() == "!")
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tok1 = tok1->next();
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skipvar.insert(tok1->varId());
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continue;
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} else if (Token::Match(tok1, "(|%oror% ! %var% %oror%") ||
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Token::Match(tok1, "(|&& %var% &&")) {
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// TODO: there are false negatives caused by this. The
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// variable should be removed from skipvar after the
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// condition
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tok1 = tok1->next();
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if (tok1->str() == "!")
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tok1 = tok1->next();
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skipvar.insert(tok1->varId());
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continue;
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}
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bool inconclusive = false;
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/**
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* @todo There are lots of false negatives here. A dereference
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* is only investigated if a few specific conditions are met.
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*/
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// dereference in assignment
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if (Token::Match(tok1, "[;{}] %var% . %var%")) {
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tok1 = tok1->next();
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if (tok1->strAt(3) == "(") {
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if (!_settings->inconclusive)
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continue;
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inconclusive = true;
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}
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}
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// dereference in assignment
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else if (Token::Match(tok1, "[{};] %var% = %var% . %var%")) {
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if (tok1->strAt(1) == tok1->strAt(3))
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continue;
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tok1 = tok1->tokAt(3);
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}
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// dereference in condition
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else if (Token::Match(tok1, "if ( !| %var% .")) {
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tok1 = tok1->tokAt(2);
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if (tok1->str() == "!")
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tok1 = tok1->next();
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}
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// dereference in function call (but not sizeof|decltype|typeof)
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else if ((Token::Match(tok1->tokAt(-2), "%var% ( %var% . %var%") && !Token::Match(tok1->tokAt(-2), "sizeof|decltype|typeof ( %var% . %var%")) ||
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Token::Match(tok1->previous(), ", %var% . %var%")) {
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// Is the function return value taken by the pointer?
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bool assignment = false;
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const unsigned int varid1(tok1->varId());
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if (varid1 == 0)
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continue;
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if (skipvar.find(varid1) != skipvar.end())
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continue;
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const Token *tok2 = tok1->previous();
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while (tok2 && !Token::Match(tok2, "[;{}]")) {
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if (Token::Match(tok2, "%varid% =", varid1)) {
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assignment = true;
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break;
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}
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tok2 = tok2->previous();
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}
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if (assignment)
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continue;
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// Is the dereference checked with a previous &&
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bool checked = false;
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for (tok2 = tok1->tokAt(-2); tok2; tok2 = tok2->previous()) {
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if (Token::Match(tok2, "[,(;{}]"))
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break;
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else if (tok2->str() == ")")
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tok2 = tok2->link();
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else if (Token::Match(tok2, "%varid% &&", varid1)) {
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checked = true;
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break;
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}
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}
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if (checked)
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continue;
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}
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// Goto next token
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else {
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continue;
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}
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// struct dereference was found - investigate if it is later
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// checked that it is not NULL
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const unsigned int varid1(tok1->varId());
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if (skipvar.find(varid1) != skipvar.end())
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continue;
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// name of struct pointer
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const std::string& varname(tok1->str());
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// is pointer local?
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bool isLocal = false;
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const Variable *var = tok1->variable();
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if (!var)
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continue;
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if (var->isLocal() || var->isArgument())
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isLocal = true;
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// member function may or may not nullify the pointer if it's global (#2647)
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if (!isLocal) {
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const Token *tok2 = tok1;
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while (Token::Match(tok2, "%var% ."))
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tok2 = tok2->tokAt(2);
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if (Token::Match(tok2,"%var% ("))
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continue;
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}
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// count { and } using tok2
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const Token* const end2 = tok1->scope()->classEnd;
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for (const Token *tok2 = tok1->tokAt(3); tok2 != end2; tok2 = tok2->next()) {
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bool unknown = false;
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// label / ?:
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if (tok2->str() == ":")
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break;
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// function call..
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else if (Token::Match(tok2, "[;{}] %var% (") && CanFunctionAssignPointer(tok2->next(), varid1, unknown)) {
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if (!_settings->inconclusive || !unknown)
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break;
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inconclusive = true;
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}
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// Reassignment of the struct
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else if (tok2->varId() == varid1) {
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if (tok2->next()->str() == "=") {
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// Avoid false positives when there is 'else if'
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// TODO: can this be handled better?
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if (tok1->strAt(-2) == "if")
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skipvar.insert(varid1);
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break;
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}
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if (Token::Match(tok2->tokAt(-2), "[,(] &"))
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break;
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}
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// Loop..
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/** @todo don't bail out if the variable is not used in the loop */
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else if (tok2->str() == "do")
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break;
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// return/break at base level => stop checking
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else if (tok2->scope()->classEnd == end2 && (tok2->str() == "return" || tok2->str() == "break"))
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break;
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// Function call: If the pointer is not a local variable it
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// might be changed by the call.
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else if (Token::Match(tok2, "[;{}] %var% (") &&
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Token::simpleMatch(tok2->linkAt(2), ") ;") && !isLocal) {
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break;
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}
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// Check if pointer is null.
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// TODO: false negatives for "if (!p || .."
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else if (!tok2->isExpandedMacro() && Token::Match(tok2, "if ( !| %varid% )|&&", varid1)) {
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// Is this variable a pointer?
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if (var->isPointer())
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nullPointerError(tok1, varname, tok2, inconclusive);
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break;
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}
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}
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}
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}
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}
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void CheckNullPointer::nullPointerByDeRefAndChec()
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{
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for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) {
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@ -784,8 +592,11 @@ void CheckNullPointer::nullPointerByDeRefAndChec()
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// Pointer dereference.
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bool unknown = false;
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if (!isPointerDeRef(tok,unknown))
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if (!isPointerDeRef(tok,unknown)) {
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if (_settings->inconclusive && unknown)
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nullPointerError(tok, tok->str(), value->condition, true);
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continue;
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}
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if (value->condition == NULL)
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nullPointerError(tok);
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@ -1004,7 +815,6 @@ void CheckNullPointer::nullPointer()
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nullPointerLinkedList();
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if (_settings->isEnabled("warning")) {
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nullPointerStructByDeRefAndChec();
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nullPointerByDeRefAndChec();
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nullPointerByCheckAndDeRef();
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nullPointerDefaultArgument();
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@ -127,12 +127,6 @@ private:
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*/
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void nullPointerLinkedList();
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/**
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* @brief Does one part of the check for nullPointer().
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* Dereferencing a struct pointer and then checking if it's NULL..
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*/
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void nullPointerStructByDeRefAndChec();
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/**
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* @brief Does one part of the check for nullPointer().
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* Dereferencing a pointer and then checking if it's NULL..
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