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Fix issue 9639: False positive: Returning object that points to local variable that will be invalid when returning (#2576) 

* Follow reference when tracking local variables

* Fix issue 9639: False positive: Returning object that points to local variable that will be invalid when returning
This commit is contained in:
Paul Fultz II 2020-03-23 16:54:53 -05:00 committed by GitHub
parent 46222d58ef
commit 5462e43161
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 44 additions and 31 deletions
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64
lib/checkautovariables.cpp
View File

@ -505,39 +505,41 @@ void CheckAutoVariables::checkVarLifetimeScope(const Token * start, const Token
for (const ValueFlow::Value& val:tok->values()) {
if (!val.isLocalLifetimeValue())
continue;
const Token * tokvalue = getParentLifetime(val.tokvalue);
if (Token::Match(tok->astParent(), "return|throw")) {
if (getPointerDepth(tok) < getPointerDepth(tokvalue))
continue;
if (!isLifetimeBorrowed(tok, mSettings))
continue;
if ((tokvalue->variable() && isInScope(tokvalue->variable()->nameToken(), scope)) ||
isDeadTemporary(mTokenizer->isCPP(), tokvalue, tok, &mSettings->library)) {
errorReturnDanglingLifetime(tok, &val);
break;
}
} else if (tokvalue->variable() && isDeadScope(tokvalue->variable()->nameToken(), tok->scope())) {
errorInvalidLifetime(tok, &val);
break;
} else if (!tokvalue->variable() && isDeadTemporary(mTokenizer->isCPP(), tokvalue, tok, &mSettings->library)) {
errorDanglingTemporaryLifetime(tok, &val);
break;
} else if (tokvalue->variable() && isInScope(tokvalue->variable()->nameToken(), tok->scope())) {
const Variable * var = nullptr;
const Token * tok2 = tok;
if (Token::simpleMatch(tok->astParent(), "=")) {
if (tok->astParent()->astOperand2() == tok) {
var = getLHSVariable(tok->astParent());
tok2 = tok->astParent()->astOperand1();
for(const LifetimeToken& lt :getLifetimeTokens(getParentLifetime(val.tokvalue))) {
const Token * tokvalue = lt.token;
if (Token::Match(tok->astParent(), "return|throw")) {
if (getPointerDepth(tok) < getPointerDepth(tokvalue))
continue;
if (!isLifetimeBorrowed(tok, mSettings))
continue;
if ((tokvalue->variable() && isInScope(tokvalue->variable()->nameToken(), scope)) ||
isDeadTemporary(mTokenizer->isCPP(), tokvalue, tok, &mSettings->library)) {
errorReturnDanglingLifetime(tok, &val);
break;
}
} else if (tok->variable() && tok->variable()->declarationId() == tok->varId()) {
var = tok->variable();
}
if (!isLifetimeBorrowed(tok, mSettings))
continue;
if (var && !var->isLocal() && !var->isArgument() && !isVariableChanged(tok->next(), tok->scope()->bodyEnd, var->declarationId(), var->isGlobal(), mSettings, mTokenizer->isCPP())) {
errorDanglngLifetime(tok2, &val);
} else if (tokvalue->variable() && isDeadScope(tokvalue->variable()->nameToken(), tok->scope())) {
errorInvalidLifetime(tok, &val);
break;
} else if (!tokvalue->variable() && isDeadTemporary(mTokenizer->isCPP(), tokvalue, tok, &mSettings->library)) {
errorDanglingTemporaryLifetime(tok, &val);
break;
} else if (tokvalue->variable() && isInScope(tokvalue->variable()->nameToken(), tok->scope())) {
const Variable * var = nullptr;
const Token * tok2 = tok;
if (Token::simpleMatch(tok->astParent(), "=")) {
if (tok->astParent()->astOperand2() == tok) {
var = getLHSVariable(tok->astParent());
tok2 = tok->astParent()->astOperand1();
}
} else if (tok->variable() && tok->variable()->declarationId() == tok->varId()) {
var = tok->variable();
}
if (!isLifetimeBorrowed(tok, mSettings))
continue;
if (var && !var->isLocal() && !var->isArgument() && !isVariableChanged(tok->next(), tok->scope()->bodyEnd, var->declarationId(), var->isGlobal(), mSettings, mTokenizer->isCPP())) {
errorDanglngLifetime(tok2, &val);
break;
}
}
}
}

11
test/testautovariables.cpp
View File

@ -2261,6 +2261,17 @@ private:
" ptr = &arr[2];\n"
"}\n");
ASSERT_EQUALS("", errout.str());
// #9639
check("struct Fred {\n"
" std::string s;\n"
"};\n"
"const Fred &getFred();\n"
"const char * f() {\n"
" const Fred &fred = getFred();\n"
" return fred.s.c_str();\n"
"}\n");
ASSERT_EQUALS("", errout.str());
}
void danglingLifetimeFunction() {