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Fix issue 9404: False positive: Either the condition 'if(x)' is redundant or there is possible null pointer dereference: a->x (#2322) 

* Fix issue 9404: False positive: Either the condition 'if(x)' is redundant or there is possible null pointer dereference: a->x

* Use simpleMatch

* Add a test case for the FP

* Check if expression is changed

* Check for no return scope

* Use simpleMatch
This commit is contained in:
Paul Fultz II 2019-11-08 01:11:41 -06:00 committed by Daniel Marjamäki
parent ba217815cb
commit c75bbbe253
6 changed files with 98 additions and 13 deletions
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44
lib/astutils.cpp
View File

@ -952,7 +952,7 @@ static bool isEscapedOrJump(const Token* tok, bool functionsScope)
return Token::Match(tok, "return|goto|throw|continue|break");
}
bool isReturnScope(const Token * const endToken, const Settings * settings, bool functionScope)
bool isReturnScope(const Token * const endToken, const Library * library, bool functionScope)
{
if (!endToken || endToken->str() != "}")
return false;
@ -965,7 +965,7 @@ bool isReturnScope(const Token * const endToken, const Settings * settings, bool
if (Token::simpleMatch(prev, "}")) {
if (Token::simpleMatch(prev->link()->tokAt(-2), "} else {"))
return isReturnScope(prev, settings, functionScope) && isReturnScope(prev->link()->tokAt(-2), settings, functionScope);
return isReturnScope(prev, library, functionScope) && isReturnScope(prev->link()->tokAt(-2), library, functionScope);
if (Token::simpleMatch(prev->link()->previous(), ") {") &&
Token::simpleMatch(prev->link()->linkAt(-1)->previous(), "switch (") &&
!Token::findsimplematch(prev->link(), "break", prev)) {
@ -974,7 +974,7 @@ bool isReturnScope(const Token * const endToken, const Settings * settings, bool
if (isEscaped(prev->link()->astTop(), functionScope))
return true;
if (Token::Match(prev->link()->previous(), "[;{}] {"))
return isReturnScope(prev, settings, functionScope);
return isReturnScope(prev, library, functionScope);
} else if (Token::simpleMatch(prev, ";")) {
if (Token::simpleMatch(prev->previous(), ") ;") && Token::Match(prev->linkAt(-1)->tokAt(-2), "[;{}] %name% (")) {
const Token * ftok = prev->linkAt(-1)->previous();
@ -984,8 +984,8 @@ bool isReturnScope(const Token * const endToken, const Settings * settings, bool
return true;
if (function->isAttributeNoreturn())
return true;
} else if (settings) {
if (settings->library.isnoreturn(ftok))
} else if (library) {
if (library->isnoreturn(ftok))
return true;
}
return false;
@ -1642,6 +1642,40 @@ struct FwdAnalysis::Result FwdAnalysis::checkRecursive(const Token *expr, const
return Result(Result::Type::BAILOUT);
}
if (mWhat == What::ValueFlow && Token::simpleMatch(tok, "if (") && Token::simpleMatch(tok->linkAt(1), ") {")) {
const Token *bodyStart = tok->linkAt(1)->next();
const Token *conditionStart = tok->next();
const Token *condTok = conditionStart->astOperand2();
if (condTok->hasKnownIntValue()) {
bool cond = condTok->values().front().intvalue;
if (cond) {
FwdAnalysis::Result result = checkRecursive(expr, bodyStart, bodyStart->link(), exprVarIds, local, true, depth);
if (result.type != Result::Type::NONE)
return result;
} else if (Token::simpleMatch(bodyStart->link(), "} else {")) {
bodyStart = bodyStart->tokAt(2);
FwdAnalysis::Result result = checkRecursive(expr, bodyStart, bodyStart->link(), exprVarIds, local, true, depth);
if (result.type != Result::Type::NONE)
return result;
}
}
tok = bodyStart->link();
if (isReturnScope(tok, &mLibrary))
return Result(Result::Type::BAILOUT);
if (Token::simpleMatch(tok, "} else {"))
tok = tok->linkAt(2);
if (!tok)
return Result(Result::Type::BAILOUT);
// Is expr changed in condition?
if (!isUnchanged(conditionStart, conditionStart->link(), exprVarIds, local))
return Result(Result::Type::BAILOUT);
// Is expr changed in condition body?
if (!isUnchanged(bodyStart, bodyStart->link(), exprVarIds, local))
return Result(Result::Type::BAILOUT);
}
if (!local && Token::Match(tok, "%name% (") && !Token::simpleMatch(tok->linkAt(1), ") {")) {
// TODO: this is a quick bailout
return Result(Result::Type::BAILOUT);

2
lib/astutils.h
View File

@ -126,7 +126,7 @@ bool isWithoutSideEffects(bool cpp, const Token* tok);
bool isUniqueExpression(const Token* tok);
/** Is scope a return scope (scope will unconditionally return) */
bool isReturnScope(const Token *endToken, const Settings * settings = nullptr, bool functionScope=false);
bool isReturnScope(const Token * const endToken, const Library * library=nullptr, bool functionScope=false);
/// Return the token to the function and the argument number
const Token * getTokenArgumentFunction(const Token * tok, int& argn);

2
lib/symboldatabase.cpp
View File

@ -1401,7 +1401,7 @@ void SymbolDatabase::createSymbolDatabaseEscapeFunctions()
Function * function = scope.function;
if (!function)
continue;
function->isEscapeFunction(isReturnScope(scope.bodyEnd, mSettings, true));
function->isEscapeFunction(isReturnScope(scope.bodyEnd, &mSettings->library, true));
}
}

2
lib/templatesimplifier.cpp
View File

@ -723,6 +723,8 @@ bool TemplateSimplifier::getTemplateDeclarations()
}
if (!tok1)
syntaxError(tok);
if (!tok1->next())
syntaxError(tok);
// Some syntax checks, see #6865
if (!tok->tokAt(2))
syntaxError(tok->next());

15
lib/valueflow.cpp
View File

@ -1678,9 +1678,12 @@ static void valueFlowReverse(TokenList *tokenlist,
if (Token::Match(tok2->previous(), "!!* %name% =")) {
Token* assignTok = const_cast<Token*>(tok2->next()->astOperand2());
if (!assignTok->hasKnownValue()) {
std::list<ValueFlow::Value> values = {val};
setTokenValue(assignTok, val, settings);
const std::string info = "Assignment from '" + assignTok->expressionString() + "'";
val.errorPath.emplace_back(assignTok, info);
std::list<ValueFlow::Value> values = {val};
if (val2.condition) {
val2.errorPath.emplace_back(assignTok, info);
setTokenValue(assignTok, val2, settings);
values.push_back(val2);
}
@ -2190,7 +2193,7 @@ static bool valueFlowForwardVariable(Token* const startToken,
++indentlevel;
else if (indentlevel >= 0 && tok2->str() == "}") {
--indentlevel;
if (indentlevel <= 0 && isReturnScope(tok2, settings) && Token::Match(tok2->link()->previous(), "else|) {")) {
if (indentlevel <= 0 && isReturnScope(tok2, &settings->library) && Token::Match(tok2->link()->previous(), "else|) {")) {
const Token *condition = tok2->link();
const bool iselse = Token::simpleMatch(condition->tokAt(-2), "} else {");
if (iselse)
@ -2240,7 +2243,7 @@ static bool valueFlowForwardVariable(Token* const startToken,
return true;
} else if (indentlevel <= 0 &&
Token::simpleMatch(tok2->link()->previous(), "else {") &&
!isReturnScope(tok2->link()->tokAt(-2), settings) &&
!isReturnScope(tok2->link()->tokAt(-2), &settings->library) &&
isVariableChanged(tok2->link(), tok2, varid, var->isGlobal(), settings, tokenlist->isCPP())) {
lowerToPossible(values);
}
@ -2506,7 +2509,7 @@ static bool valueFlowForwardVariable(Token* const startToken,
}
// stop after conditional return scopes that are executed
if (isReturnScope(end, settings)) {
if (isReturnScope(end, &settings->library)) {
std::list<ValueFlow::Value>::iterator it;
for (it = values.begin(); it != values.end();) {
if (conditionIsTrue(tok2->next()->astOperand2(), getProgramMemory(tok2, varid, *it)))
@ -4375,7 +4378,7 @@ struct ValueFlowConditionHandler {
continue;
}
bool dead_if = isReturnScope(after, settings) ||
bool dead_if = isReturnScope(after, &settings->library) ||
(tok->astParent() && Token::simpleMatch(tok->astParent()->previous(), "while (") &&
!isBreakScope(after));
bool dead_else = false;
@ -4387,7 +4390,7 @@ struct ValueFlowConditionHandler {
bailout(tokenlist, errorLogger, after, "possible noreturn scope");
continue;
}
dead_else = isReturnScope(after, settings);
dead_else = isReturnScope(after, &settings->library);
}
if (dead_if && dead_else)

46
test/testnullpointer.cpp
View File

@ -82,7 +82,9 @@ private:
TEST_CASE(nullpointer40);
TEST_CASE(nullpointer41);
TEST_CASE(nullpointer42);
TEST_CASE(nullpointer43); // #9404
TEST_CASE(nullpointer44); // #9395, #9423
TEST_CASE(nullpointer45);
TEST_CASE(nullpointer_addressOf); // address of
TEST_CASE(nullpointerSwitch); // #2626
TEST_CASE(nullpointer_cast); // #4692
@ -1538,6 +1540,17 @@ private:
errout.str());
}
void nullpointer43() {
check("struct A { int* x; };\n"
"void f(A* a) {\n"
" int * x = a->x;\n"
" if (x) {\n"
" (void)*a->x;\n"
" }\n"
"}\n");
ASSERT_EQUALS("", errout.str());
}
void nullpointer44() {
// #9395
check("int foo( ) {\n"
@ -1567,6 +1580,39 @@ private:
ASSERT_EQUALS("", errout.str());
}
void nullpointer45() {
check("struct a {\n"
" a *b() const;\n"
"};\n"
"void g() { throw 0; }\n"
"a h(a * c) {\n"
" if (c && c->b()) {}\n"
" if (!c)\n"
" g();\n"
" if (!c->b())\n"
" g();\n"
" a d = *c->b();\n"
" return d;\n"
"}\n");
ASSERT_EQUALS("", errout.str());
check("struct a {\n"
" a *b() const;\n"
"};\n"
"void e() { throw 0; }\n"
"a f() {\n"
" a *c = 0;\n"
" if (0 && c->b()) {}\n"
" if (!c)\n"
" e();\n"
" if (!c->b())\n"
" e();\n"
" a d = *c->b();\n"
" return d;\n"
"}\n");
ASSERT_EQUALS("", errout.str());
}
void nullpointer_addressOf() { // address of
check("void f() {\n"
" struct X *x = 0;\n"