cppcheck/lib/checkautovariables.cpp

/*
 * Cppcheck - A tool for static C/C++ code analysis
 * Copyright (C) 2007-2021 Cppcheck team.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

//---------------------------------------------------------------------------
// Auto variables checks
//---------------------------------------------------------------------------

#include "checkautovariables.h"

#include "astutils.h"
#include "library.h"
#include "settings.h"
#include "symboldatabase.h"
#include "token.h"
#include "tokenize.h"
#include "valueflow.h"

#include <algorithm>
#include <list>

//---------------------------------------------------------------------------


// Register this check class into cppcheck by creating a static instance of it..
namespace {
    CheckAutoVariables instance;
}

static const CWE CWE398(398U);  // Indicator of Poor Code Quality
static const CWE CWE562(562U);  // Return of Stack Variable Address
static const CWE CWE590(590U);  // Free of Memory not on the Heap

static bool isPtrArg(const Token *tok)
{
    const Variable *var = tok->variable();
    return (var && var->isArgument() && var->isPointer());
}

static bool isArrayArg(const Token *tok)
{
    const Variable *var = tok->variable();
    return (var && var->isArgument() && var->isArray());
}

static bool isArrayVar(const Token *tok)
{
    const Variable *var = tok->variable();
    return (var && var->isArray());
}

static bool isRefPtrArg(const Token *tok)
{
    const Variable *var = tok->variable();
    return (var && var->isArgument() && var->isReference() && var->isPointer());
}

static bool isNonReferenceArg(const Token *tok)
{
    const Variable *var = tok->variable();
    return (var && var->isArgument() && !var->isReference() && (var->isPointer() || (var->valueType() && var->valueType()->type >= ValueType::Type::CONTAINER) || var->type()));
}

static bool isAutoVar(const Token *tok)
{
    const Variable *var = tok->variable();

    if (!var || !var->isLocal() || var->isStatic())
        return false;

    if (var->isReference()) {
        // address of reference variable can be taken if the address
        // of the variable it points at is not a auto-var
        // TODO: check what the reference variable references.
        return false;
    }

    if (Token::Match(tok, "%name% .|::")) {
        do {
            tok = tok->tokAt(2);
        } while (Token::Match(tok, "%name% .|::"));
        if (Token::Match(tok, "%name% ("))
            return false;
    }
    return true;
}

static bool isAutoVarArray(const Token *tok)
{
    if (!tok)
        return false;

    // &x[..]
    if (tok->isUnaryOp("&") && Token::simpleMatch(tok->astOperand1(), "["))
        return isAutoVarArray(tok->astOperand1()->astOperand1());

    // x+y
    if (tok->str() == "+")
        return isAutoVarArray(tok->astOperand1()) || isAutoVarArray(tok->astOperand2());

    // x-intexpr
    if (tok->str() == "-")
        return isAutoVarArray(tok->astOperand1()) &&
               tok->astOperand2() &&
               tok->astOperand2()->valueType() &&
               tok->astOperand2()->valueType()->isIntegral();

    const Variable *var = tok->variable();
    if (!var)
        return false;

    // Variable
    if (var->isLocal() && !var->isStatic() && var->isArray() && !var->isPointer())
        return true;

    // ValueFlow
    if (var->isPointer() && !var->isArgument()) {
        for (std::list<ValueFlow::Value>::const_iterator it = tok->values().begin(); it != tok->values().end(); ++it) {
            const ValueFlow::Value &val = *it;
            if (val.isTokValue() && isAutoVarArray(val.tokvalue))
                return true;
        }
    }

    return false;
}

// Verification that we really take the address of a local variable
static bool checkRvalueExpression(const Token * const vartok)
{
    const Variable * const var = vartok->variable();
    if (var == nullptr)
        return false;

    if (Token::Match(vartok->previous(), "& %name% [") && var->isPointer())
        return false;

    const Token * const next = vartok->next();
    // &a.b[0]
    if (Token::Match(vartok, "%name% . %var% [") && !var->isPointer()) {
        const Variable *var2 = next->next()->variable();
        return var2 && !var2->isPointer();
    }

    return ((next->str() != "." || (!var->isPointer() && (!var->isClass() || var->type()))) && next->strAt(2) != ".");
}

static bool isAddressOfLocalVariable(const Token *expr)
{
    if (!expr)
        return false;
    if (Token::Match(expr, "+|-"))
        return isAddressOfLocalVariable(expr->astOperand1()) || isAddressOfLocalVariable(expr->astOperand2());
    if (expr->isCast())
        return isAddressOfLocalVariable(expr->astOperand2() ? expr->astOperand2() : expr->astOperand1());
    if (expr->isUnaryOp("&")) {
        const Token *op = expr->astOperand1();
        bool deref = false;
        while (Token::Match(op, ".|[")) {
            if (op->originalName() == "->")
                return false;
            if (op->str() == "[")
                deref = true;
            op = op->astOperand1();
        }
        return op && isAutoVar(op) && (!deref || !op->variable()->isPointer());
    }
    return false;
}

static bool variableIsUsedInScope(const Token* start, nonneg int varId, const Scope *scope)
{
    if (!start) // Ticket #5024
        return false;

    for (const Token *tok = start; tok && tok != scope->bodyEnd; tok = tok->next()) {
        if (tok->varId() == varId)
            return true;
        const Scope::ScopeType scopeType = tok->scope()->type;
        if (scopeType == Scope::eFor || scopeType == Scope::eDo || scopeType == Scope::eWhile) // In case of loops, better checking would be necessary
            return true;
        if (Token::simpleMatch(tok, "asm ("))
            return true;
    }
    return false;
}

void CheckAutoVariables::assignFunctionArg()
{
    const bool printStyle = mSettings->severity.isEnabled(Severity::style);
    const bool printWarning = mSettings->severity.isEnabled(Severity::warning);
    if (!printStyle && !printWarning)
        return;

    const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase();
    for (const Scope * scope : symbolDatabase->functionScopes) {
        for (const Token *tok = scope->bodyStart; tok && tok != scope->bodyEnd; tok = tok->next()) {
            // TODO: What happens if this is removed?
            if (tok->astParent())
                continue;
            if (!(tok->isAssignmentOp() || Token::Match(tok, "++|--")) || !Token::Match(tok->astOperand1(), "%var%"))
                continue;
            const Token* const vartok = tok->astOperand1();
            if (isNonReferenceArg(vartok) &&
                !Token::Match(vartok->next(), "= %varid% ;", vartok->varId()) &&
                !variableIsUsedInScope(Token::findsimplematch(vartok->next(), ";"), vartok->varId(), scope) &&
                !Token::findsimplematch(vartok, "goto", scope->bodyEnd)) {
                if (vartok->variable()->isPointer() && printWarning)
                    errorUselessAssignmentPtrArg(vartok);
                else if (printStyle)
                    errorUselessAssignmentArg(vartok);
            }
        }
    }
}

void CheckAutoVariables::autoVariables()
{
    const bool printInconclusive = mSettings->certainty.isEnabled(Certainty::inconclusive);
    const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase();
    for (const Scope * scope : symbolDatabase->functionScopes) {
        for (const Token *tok = scope->bodyStart; tok && tok != scope->bodyEnd; tok = tok->next()) {
            // Skip lambda..
            if (const Token *lambdaEndToken = findLambdaEndToken(tok)) {
                tok = lambdaEndToken;
                continue;
            }
            // Critical assignment
            if (Token::Match(tok, "[;{}] %var% = & %var%") && isRefPtrArg(tok->next()) && isAutoVar(tok->tokAt(4))) {
                if (checkRvalueExpression(tok->tokAt(4)))
                    checkAutoVariableAssignment(tok->next(), false);
            } else if (Token::Match(tok, "[;{}] * %var% =") && isPtrArg(tok->tokAt(2)) && isAddressOfLocalVariable(tok->tokAt(3)->astOperand2())) {
                checkAutoVariableAssignment(tok->next(), false);
            } else if (Token::Match(tok, "[;{}] %var% . %var% =") && isPtrArg(tok->next()) && isAddressOfLocalVariable(tok->tokAt(4)->astOperand2())) {
                checkAutoVariableAssignment(tok->next(), false);
            } else if (Token::Match(tok, "[;{}] %var% . %var% = %var% ;")) {
                // TODO: check if the parameter is only changed temporarily (#2969)
                if (printInconclusive && isPtrArg(tok->next())) {
                    if (isAutoVarArray(tok->tokAt(5)))
                        checkAutoVariableAssignment(tok->next(), true);
                }
                tok = tok->tokAt(5);
            } else if (Token::Match(tok, "[;{}] * %var% = %var% ;")) {
                const Variable * var1 = tok->tokAt(2)->variable();
                if (var1 && var1->isArgument() && Token::Match(var1->nameToken()->tokAt(-3), "%type% * *")) {
                    if (isAutoVarArray(tok->tokAt(4)))
                        checkAutoVariableAssignment(tok->next(), false);
                }
                tok = tok->tokAt(4);
            } else if (Token::Match(tok, "[;{}] %var% [") && Token::simpleMatch(tok->linkAt(2), "] =") &&
                       (isPtrArg(tok->next()) || isArrayArg(tok->next())) && isAddressOfLocalVariable(tok->linkAt(2)->next()->astOperand2())) {
                errorAutoVariableAssignment(tok->next(), false);
            }
            // Invalid pointer deallocation
            else if ((Token::Match(tok, "%name% ( %var%|%str% ) ;") && mSettings->library.getDeallocFuncInfo(tok)) ||
                     (mTokenizer->isCPP() && Token::Match(tok, "delete [| ]| (| %var%|%str% !!["))) {
                tok = Token::findmatch(tok->next(), "%var%|%str%");
                if (isArrayVar(tok) || tok->tokType() == Token::eString)
                    errorInvalidDeallocation(tok, nullptr);
                else if (tok->variable() && tok->variable()->isPointer()) {
                    for (const ValueFlow::Value &v : tok->values()) {
                        if (!(v.isTokValue()))
                            continue;
                        if (isArrayVar(v.tokvalue) || ((v.tokvalue->tokType() == Token::eString) && !v.isImpossible())) {
                            errorInvalidDeallocation(tok, &v);
                            break;
                        }
                    }
                }
            } else if ((Token::Match(tok, "%name% ( & %var% ) ;") && mSettings->library.getDeallocFuncInfo(tok)) ||
                       (mTokenizer->isCPP() && Token::Match(tok, "delete [| ]| (| & %var% !!["))) {
                tok = Token::findmatch(tok->next(), "%var%");
                if (isAutoVar(tok))
                    errorInvalidDeallocation(tok, nullptr);
            }
        }
    }
}

bool CheckAutoVariables::checkAutoVariableAssignment(const Token *expr, bool inconclusive, const Token *startToken)
{
    if (!startToken)
        startToken = Token::findsimplematch(expr, "=")->next();
    for (const Token *tok = startToken; tok; tok = tok->next()) {
        if (tok->str() == "}" && tok->scope()->type == Scope::ScopeType::eFunction)
            errorAutoVariableAssignment(expr, inconclusive);

        if (Token::Match(tok, "return|throw|break|continue")) {
            errorAutoVariableAssignment(expr, inconclusive);
            return true;
        }
        if (Token::simpleMatch(tok, "=")) {
            const Token *lhs = tok;
            while (Token::Match(lhs->previous(), "%name%|.|*"))
                lhs = lhs->previous();
            const Token *e = expr;
            while (e->str() != "=" && lhs->str() == e->str()) {
                e = e->next();
                lhs = lhs->next();
            }
            if (lhs->str() == "=")
                return false;
        }

        if (Token::simpleMatch(tok, "if (")) {
            const Token *ifStart = tok->linkAt(1)->next();
            return checkAutoVariableAssignment(expr, inconclusive, ifStart) || checkAutoVariableAssignment(expr, inconclusive, ifStart->link()->next());
        }
        if (Token::simpleMatch(tok, "} else {"))
            tok = tok->linkAt(2);
    }
    return false;
}

//---------------------------------------------------------------------------

void CheckAutoVariables::errorReturnAddressToAutoVariable(const Token *tok)
{
    reportError(tok, Severity::error, "returnAddressOfAutoVariable", "Address of an auto-variable returned.", CWE562, Certainty::normal);
}

void CheckAutoVariables::errorReturnAddressToAutoVariable(const Token *tok, const ValueFlow::Value *value)
{
    reportError(tok, Severity::error, "returnAddressOfAutoVariable", "Address of auto-variable '" + value->tokvalue->astOperand1()->expressionString() + "' returned", CWE562, Certainty::normal);
}

void CheckAutoVariables::errorReturnPointerToLocalArray(const Token *tok)
{
    reportError(tok, Severity::error, "returnLocalVariable", "Pointer to local array variable returned.", CWE562, Certainty::normal);
}

void CheckAutoVariables::errorAutoVariableAssignment(const Token *tok, bool inconclusive)
{
    if (!inconclusive) {
        reportError(tok, Severity::error, "autoVariables",
                    "Address of local auto-variable assigned to a function parameter.\n"
                    "Dangerous assignment - the function parameter is assigned the address of a local "
                    "auto-variable. Local auto-variables are reserved from the stack which "
                    "is freed when the function ends. So the pointer to a local variable "
                    "is invalid after the function ends.", CWE562, Certainty::normal);
    } else {
        reportError(tok, Severity::error, "autoVariables",
                    "Address of local auto-variable assigned to a function parameter.\n"
                    "Function parameter is assigned the address of a local auto-variable. "
                    "Local auto-variables are reserved from the stack which is freed when "
                    "the function ends. The address is invalid after the function ends and it "
                    "might 'leak' from the function through the parameter.",
                    CWE562,
                    Certainty::inconclusive);
    }
}

void CheckAutoVariables::errorReturnAddressOfFunctionParameter(const Token *tok, const std::string &varname)
{
    reportError(tok, Severity::error, "returnAddressOfFunctionParameter",
                "$symbol:" + varname + "\n"
                "Address of function parameter '$symbol' returned.\n"
                "Address of the function parameter '$symbol' becomes invalid after the function exits because "
                "function parameters are stored on the stack which is freed when the function exits. Thus the returned "
                "value is invalid.", CWE562, Certainty::normal);
}

void CheckAutoVariables::errorUselessAssignmentArg(const Token *tok)
{
    reportError(tok,
                Severity::style,
                "uselessAssignmentArg",
                "Assignment of function parameter has no effect outside the function.", CWE398, Certainty::normal);
}

void CheckAutoVariables::errorUselessAssignmentPtrArg(const Token *tok)
{
    reportError(tok,
                Severity::warning,
                "uselessAssignmentPtrArg",
                "Assignment of function parameter has no effect outside the function. Did you forget dereferencing it?", CWE398, Certainty::normal);
}

//---------------------------------------------------------------------------

static bool isInScope(const Token * tok, const Scope * scope)
{
    if (!tok)
        return false;
    if (!scope)
        return false;
    const Variable * var = tok->variable();
    if (var && (var->isGlobal() || var->isStatic() || var->isExtern()))
        return false;
    if (tok->scope() && tok->scope()->isNestedIn(scope))
        return true;
    if (!var)
        return false;
    if (var->isArgument() && !var->isReference()) {
        const Scope * tokScope = tok->scope();
        if (!tokScope)
            return false;
        for (const Scope * argScope:tokScope->nestedList) {
            if (argScope && argScope->isNestedIn(scope))
                return true;
        }
    }
    return false;
}

static bool isDeadScope(const Token * tok, const Scope * scope)
{
    if (!tok)
        return false;
    if (!scope)
        return false;
    const Variable * var = tok->variable();
    if (var && (!var->isLocal() || var->isStatic() || var->isExtern()))
        return false;
    if (tok->scope() && tok->scope()->bodyEnd != scope->bodyEnd && precedes(tok->scope()->bodyEnd, scope->bodyEnd))
        return true;
    return false;
}

static int getPointerDepth(const Token *tok)
{
    if (!tok)
        return 0;
    if (tok->valueType())
        return tok->valueType()->pointer;
    int n = 0;
    std::pair<const Token*, const Token*> decl = Token::typeDecl(tok);
    for (const Token* tok2 = decl.first; tok2 != decl.second; tok2 = tok2->next())
        if (Token::simpleMatch(tok, "*"))
            n++;
    return n;
}

static bool isDeadTemporary(bool cpp, const Token* tok, const Token* expr, const Library* library)
{
    if (!isTemporary(cpp, tok, library))
        return false;
    if (expr) {
        if (!precedes(nextAfterAstRightmostLeaf(tok->astTop()), nextAfterAstRightmostLeaf(expr->astTop())))
            return false;
        const Token* parent = tok->astParent();
        // Is in a for loop
        if (astIsRHS(tok) && Token::simpleMatch(parent, ":") && Token::simpleMatch(parent->astParent(), "(") && Token::simpleMatch(parent->astParent()->previous(), "for (")) {
            const Token* braces = parent->astParent()->link()->next();
            if (precedes(braces, expr) && precedes(expr, braces->link()))
                return false;
        }
    }
    return true;
}

static bool isEscapedReference(const Variable* var)
{
    if (!var)
        return false;
    if (!var->isReference())
        return false;
    if (!var->declEndToken())
        return false;
    if (!Token::simpleMatch(var->declEndToken(), "="))
        return false;
    const Token* vartok = var->declEndToken()->astOperand2();
    return !isTemporary(true, vartok, nullptr, false);
}

static bool isDanglingSubFunction(const Token* tokvalue, const Token* tok)
{
    if (!tokvalue)
        return false;
    const Variable* var = tokvalue->variable();
    if (!var->isLocal())
        return false;
    Function* f = Scope::nestedInFunction(tok->scope());
    if (!f)
        return false;
    const Token* parent = tokvalue->astParent();
    while (parent && !Token::Match(parent->previous(), "%name% (")) {
        parent = parent->astParent();
    }
    if (!Token::simpleMatch(parent, "("))
        return false;
    return exprDependsOnThis(parent);
}

static const Variable* getParentVar(const Token* tok)
{
    if (!tok)
        return nullptr;
    if (Token::simpleMatch(tok, "."))
        return getParentVar(tok->astOperand1());
    return tok->variable();
}

static bool isAssignedToNonLocal(const Token* tok)
{
    if (!Token::simpleMatch(tok->astParent(), "="))
        return false;
    if (!astIsRHS(tok))
        return false;
    const Variable* var = getParentVar(tok->astParent()->astOperand1());
    if (!var)
        return false;
    return !var->isLocal() || var->isStatic();
}

static std::vector<const Token*> getParentMembers(const Token* tok)
{
    if (!tok)
        return {};
    if (!Token::simpleMatch(tok->astParent(), "."))
        return {tok};
    const Token* parent = tok;
    while (Token::simpleMatch(parent->astParent(), "."))
        parent = parent->astParent();
    std::vector<const Token*> result;
    for (const Token* tok2 : astFlatten(parent, ".")) {
        if (Token::simpleMatch(tok2, "(") && Token::simpleMatch(tok2->astOperand1(), ".")) {
            std::vector<const Token*> sub = getParentMembers(tok2->astOperand1());
            result.insert(result.end(), sub.begin(), sub.end());
        }
        result.push_back(tok2);
    }
    return result;
}

static const Token* getParentLifetime(bool cpp, const Token* tok, const Library* library)
{
    std::vector<const Token*> members = getParentMembers(tok);
    if (members.size() < 2)
        return tok;
    // Find the first local variable or temporary
    auto it = std::find_if(members.rbegin(), members.rend(), [&](const Token* tok2) {
        const Variable* var = tok2->variable();
        if (var) {
            return var->isLocal() || var->isArgument();
        } else {
            return isTemporary(cpp, tok2, library);
        }
    });
    if (it == members.rend())
        return tok;
    // If any of the submembers are borrowed types then stop
    if (std::any_of(it.base() - 1, members.end() - 1, [&](const Token* tok2) {
        if (astIsPointer(tok2) || astIsContainerView(tok2) || astIsIterator(tok2))
            return true;
        if (!astIsUniqueSmartPointer(tok2)) {
            if (astIsSmartPointer(tok2))
                return true;
            const Token* dotTok = tok2->next();
            if (!Token::simpleMatch(dotTok, ".")) {
                const Token* endTok = nextAfterAstRightmostLeaf(tok2);
                if (Token::simpleMatch(endTok, "."))
                    dotTok = endTok;
                else if (Token::simpleMatch(endTok->next(), "."))
                    dotTok = endTok->next();
            }
            // If we are dereferencing the member variable then treat it as borrowed
            if (Token::simpleMatch(dotTok, ".") && dotTok->originalName() == "->")
                return true;
        }
        const Variable* var = tok2->variable();
        return var && var->isReference();
    }))
        return nullptr;
    return *it;
}

void CheckAutoVariables::checkVarLifetimeScope(const Token * start, const Token * end)
{
    const bool printInconclusive = mSettings->certainty.isEnabled(Certainty::inconclusive);
    if (!start)
        return;
    const Scope * scope = start->scope();
    if (!scope)
        return;
    // If the scope is not set correctly then skip checking it
    if (scope->bodyStart != start)
        return;
    bool returnRef = Function::returnsReference(scope->function);
    for (const Token *tok = start; tok && tok != end; tok = tok->next()) {
        // Return reference from function
        if (returnRef && Token::simpleMatch(tok->astParent(), "return")) {
            for (const LifetimeToken& lt : getLifetimeTokens(tok, true)) {
                if (!printInconclusive && lt.inconclusive)
                    continue;
                const Variable* var = lt.token->variable();
                if (var && !var->isGlobal() && !var->isStatic() && !var->isReference() && !var->isRValueReference() &&
                    isInScope(var->nameToken(), tok->scope())) {
                    errorReturnReference(tok, lt.errorPath, lt.inconclusive);
                    break;
                } else if (isDeadTemporary(mTokenizer->isCPP(), lt.token, nullptr, &mSettings->library)) {
                    errorReturnTempReference(tok, lt.errorPath, lt.inconclusive);
                    break;
                }
            }
            // Assign reference to non-local variable
        } else if (Token::Match(tok->previous(), "&|&& %var% =") && tok->astParent() == tok->next() &&
                   tok->variable() && tok->variable()->nameToken() == tok &&
                   tok->variable()->declarationId() == tok->varId() && tok->variable()->isStatic() &&
                   !tok->variable()->isArgument()) {
            ErrorPath errorPath;
            const Variable *var = getLifetimeVariable(tok, errorPath);
            if (var && isInScope(var->nameToken(), tok->scope())) {
                errorDanglingReference(tok, var, errorPath);
                continue;
            }
            // Reference to temporary
        } else if (tok->variable() && (tok->variable()->isReference() || tok->variable()->isRValueReference())) {
            for (const LifetimeToken& lt : getLifetimeTokens(getParentLifetime(tok))) {
                if (!printInconclusive && lt.inconclusive)
                    continue;
                const Token * tokvalue = lt.token;
                if (isDeadTemporary(mTokenizer->isCPP(), tokvalue, tok, &mSettings->library)) {
                    errorDanglingTempReference(tok, lt.errorPath, lt.inconclusive);
                    break;
                }
            }
        }
        const bool escape = Token::Match(tok->astParent(), "return|throw");
        std::unordered_set<const Token*> exprs;
        for (const ValueFlow::Value& val:tok->values()) {
            if (!val.isLocalLifetimeValue() && !val.isSubFunctionLifetimeValue())
                continue;
            if (!printInconclusive && val.isInconclusive())
                continue;
            const Token* parent = getParentLifetime(mTokenizer->isCPP(), val.tokvalue, &mSettings->library);
            if (!exprs.insert(parent).second)
                continue;
            for (const LifetimeToken& lt : getLifetimeTokens(parent, escape || isAssignedToNonLocal(tok))) {
                const Token * tokvalue = lt.token;
                if (val.isLocalLifetimeValue()) {
                    if (escape) {
                        if (getPointerDepth(tok) < getPointerDepth(tokvalue))
                            continue;
                        if (!isLifetimeBorrowed(tok, mSettings))
                            continue;
                        if (tokvalue->exprId() == tok->exprId() && !(tok->variable() && tok->variable()->isArray()) &&
                            !astIsContainerView(tok->astParent()))
                            continue;
                        if ((tokvalue->variable() && !isEscapedReference(tokvalue->variable()) &&
                             isInScope(tokvalue->variable()->nameToken(), scope)) ||
                            isDeadTemporary(mTokenizer->isCPP(), tokvalue, nullptr, &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, tokvalue);
                        break;
                    }
                }
                if (tokvalue->variable() && (isInScope(tokvalue->variable()->nameToken(), tok->scope()) ||
                                             (val.isSubFunctionLifetimeValue() && isDanglingSubFunction(tokvalue, tok)))) {
                    const Variable * var = nullptr;
                    const Token * tok2 = tok;
                    if (Token::simpleMatch(tok->astParent(), "=")) {
                        if (astIsRHS(tok)) {
                            var = getParentVar(tok->astParent()->astOperand1());
                            tok2 = tok->astParent()->astOperand1();
                        }
                    } else if (tok->variable() && tok->variable()->declarationId() == tok->varId()) {
                        var = tok->variable();
                    }
                    if (!isLifetimeBorrowed(tok, mSettings))
                        continue;
                    const Token* nextTok = nextAfterAstRightmostLeaf(tok->astTop());
                    if (!nextTok)
                        nextTok = tok->next();
                    if (var && !var->isLocal() && !var->isArgument() &&
                        !isVariableChanged(nextTok,
                                           tok->scope()->bodyEnd,
                                           var->declarationId(),
                                           var->isGlobal(),
                                           mSettings,
                                           mTokenizer->isCPP())) {
                        errorDanglngLifetime(tok2, &val);
                        break;
                    }
                }
            }
        }
        const Token *lambdaEndToken = findLambdaEndToken(tok);
        if (lambdaEndToken) {
            checkVarLifetimeScope(lambdaEndToken->link(), lambdaEndToken);
            tok = lambdaEndToken;
        }
        if (tok->str() == "{" && tok->scope()) {
            // Check functions in local classes
            if (tok->scope()->type == Scope::eClass ||
                tok->scope()->type == Scope::eStruct ||
                tok->scope()->type == Scope::eUnion) {
                for (const Function& f:tok->scope()->functionList) {
                    if (f.functionScope)
                        checkVarLifetimeScope(f.functionScope->bodyStart, f.functionScope->bodyEnd);
                }
                tok = tok->link();
            }
        }
    }
}

void CheckAutoVariables::checkVarLifetime()
{
    const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase();
    for (const Scope * scope : symbolDatabase->functionScopes) {
        if (!scope->function)
            continue;
        checkVarLifetimeScope(scope->bodyStart, scope->bodyEnd);
    }
}

void CheckAutoVariables::errorReturnDanglingLifetime(const Token *tok, const ValueFlow::Value *val)
{
    const bool inconclusive = val ? val->isInconclusive() : false;
    ErrorPath errorPath = val ? val->errorPath : ErrorPath();
    std::string msg = "Returning " + lifetimeMessage(tok, val, errorPath);
    errorPath.emplace_back(tok, "");
    reportError(errorPath, Severity::error, "returnDanglingLifetime", msg + " that will be invalid when returning.", CWE562, inconclusive ? Certainty::inconclusive : Certainty::normal);
}

void CheckAutoVariables::errorInvalidLifetime(const Token *tok, const ValueFlow::Value* val)
{
    const bool inconclusive = val ? val->isInconclusive() : false;
    ErrorPath errorPath = val ? val->errorPath : ErrorPath();
    std::string msg = "Using " + lifetimeMessage(tok, val, errorPath);
    errorPath.emplace_back(tok, "");
    reportError(errorPath, Severity::error, "invalidLifetime", msg + " that is out of scope.", CWE562, inconclusive ? Certainty::inconclusive : Certainty::normal);
}

void CheckAutoVariables::errorDanglingTemporaryLifetime(const Token* tok, const ValueFlow::Value* val, const Token* tempTok)
{
    const bool inconclusive = val ? val->isInconclusive() : false;
    ErrorPath errorPath = val ? val->errorPath : ErrorPath();
    std::string msg = "Using " + lifetimeMessage(tok, val, errorPath);
    errorPath.emplace_back(tempTok, "Temporary created here.");
    errorPath.emplace_back(tok, "");
    reportError(errorPath,
                Severity::error,
                "danglingTemporaryLifetime",
                msg + " that is a temporary.",
                CWE562,
                inconclusive ? Certainty::inconclusive : Certainty::normal);
}

void CheckAutoVariables::errorDanglngLifetime(const Token *tok, const ValueFlow::Value *val)
{
    const bool inconclusive = val ? val->isInconclusive() : false;
    ErrorPath errorPath = val ? val->errorPath : ErrorPath();
    std::string tokName = tok ? tok->expressionString() : "x";
    std::string msg = "Non-local variable '" + tokName + "' will use " + lifetimeMessage(tok, val, errorPath);
    errorPath.emplace_back(tok, "");
    reportError(errorPath, Severity::error, "danglingLifetime", msg + ".", CWE562, inconclusive ? Certainty::inconclusive : Certainty::normal);
}

void CheckAutoVariables::errorDanglingTempReference(const Token* tok, ErrorPath errorPath, bool inconclusive)
{
    errorPath.emplace_back(tok, "");
    reportError(
        errorPath, Severity::error, "danglingTempReference", "Using reference to dangling temporary.", CWE562, inconclusive ? Certainty::inconclusive : Certainty::normal);
}

void CheckAutoVariables::errorReturnReference(const Token* tok, ErrorPath errorPath, bool inconclusive)
{
    errorPath.emplace_back(tok, "");
    reportError(
        errorPath, Severity::error, "returnReference", "Reference to local variable returned.", CWE562, inconclusive ? Certainty::inconclusive : Certainty::normal);
}

void CheckAutoVariables::errorDanglingReference(const Token *tok, const Variable *var, ErrorPath errorPath)
{
    std::string tokName = tok ? tok->str() : "x";
    std::string varName = var ? var->name() : "y";
    std::string msg = "Non-local reference variable '" + tokName + "' to local variable '" + varName + "'";
    errorPath.emplace_back(tok, "");
    reportError(errorPath, Severity::error, "danglingReference", msg, CWE562, Certainty::normal);
}

void CheckAutoVariables::errorReturnTempReference(const Token* tok, ErrorPath errorPath, bool inconclusive)
{
    errorPath.emplace_back(tok, "");
    reportError(
        errorPath, Severity::error, "returnTempReference", "Reference to temporary returned.", CWE562, inconclusive ? Certainty::inconclusive : Certainty::normal);
}

void CheckAutoVariables::errorInvalidDeallocation(const Token *tok, const ValueFlow::Value *val)
{
    const Variable *var = val ? val->tokvalue->variable() : (tok ? tok->variable() : nullptr);

    std::string type = "auto-variable";
    if (tok && tok->tokType() == Token::eString)
        type = "string literal";
    else if (val && val->tokvalue->tokType() == Token::eString)
        type = "pointer pointing to a string literal";
    else if (var) {
        if (var->isGlobal())
            type = "global variable";
        else if (var->isStatic())
            type = "static variable";
    }

    if (val)
        type += " (" + val->tokvalue->str() + ")";

    reportError(getErrorPath(tok, val, "Deallocating memory that was not dynamically allocated"),
                Severity::error,
                "autovarInvalidDeallocation",
                "Deallocation of an " + type + " results in undefined behaviour.\n"
                "The deallocation of an " + type + " results in undefined behaviour. You should only free memory "
                "that has been allocated dynamically.", CWE590, Certainty::normal);
}