cppcheck/lib/reverseanalyzer.cpp

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/*
* Cppcheck - A tool for static C/C++ code analysis
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* Copyright (C) 2007-2022 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/>.
*/
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#include "reverseanalyzer.h"
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#include "analyzer.h"
#include "astutils.h"
#include "errortypes.h"
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#include "forwardanalyzer.h"
#include "mathlib.h"
#include "settings.h"
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#include "symboldatabase.h"
#include "token.h"
#include "valueptr.h"
#include <algorithm>
#include <cstddef>
#include <string>
#include <tuple>
#include <utility>
#include <vector>
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struct ReverseTraversal {
ReverseTraversal(const ValuePtr<Analyzer>& analyzer, const Settings* settings)
: analyzer(analyzer), settings(settings)
{}
ValuePtr<Analyzer> analyzer;
const Settings* settings;
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std::pair<bool, bool> evalCond(const Token* tok) {
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std::vector<MathLib::bigint> result = analyzer->evaluate(tok);
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// TODO: We should convert to bool
const bool checkThen = std::any_of(result.begin(), result.end(), [](int x) {
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return x == 1;
});
const bool checkElse = std::any_of(result.begin(), result.end(), [](int x) {
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return x == 0;
});
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return std::make_pair(checkThen, checkElse);
}
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bool update(Token* tok) {
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Analyzer::Action action = analyzer->analyze(tok, Analyzer::Direction::Reverse);
if (!action.isNone())
analyzer->update(tok, action, Analyzer::Direction::Reverse);
if (action.isInconclusive() && !analyzer->lowerToInconclusive())
return false;
if (action.isInvalid())
return false;
return true;
}
static Token* getParentFunction(Token* tok)
{
if (!tok)
return nullptr;
if (!tok->astParent())
return nullptr;
int argn = -1;
if (Token* ftok = getTokenArgumentFunction(tok, argn)) {
while (!Token::Match(ftok, "(|{")) {
if (!ftok)
return nullptr;
if (ftok->index() >= tok->index())
return nullptr;
if (ftok->link())
ftok = ftok->link()->next();
else
ftok = ftok->next();
}
if (ftok == tok)
return nullptr;
return ftok;
}
return nullptr;
}
static Token* getTopFunction(Token* tok)
{
if (!tok)
return nullptr;
if (!tok->astParent())
return tok;
Token* parent = tok;
Token* top = tok;
while ((parent = getParentFunction(parent)))
top = parent;
return top;
}
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bool updateRecursive(Token* start) {
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bool continueB = true;
visitAstNodes(start, [&](Token* tok) {
const Token* parent = tok->astParent();
while (Token::simpleMatch(parent, ":"))
parent = parent->astParent();
if (isUnevaluated(tok) || isDeadCode(tok, parent))
return ChildrenToVisit::none;
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continueB &= update(tok);
if (continueB)
return ChildrenToVisit::op1_and_op2;
else
return ChildrenToVisit::done;
});
return continueB;
}
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Analyzer::Action analyzeRecursive(const Token* start) {
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Analyzer::Action result = Analyzer::Action::None;
visitAstNodes(start, [&](const Token* tok) {
result |= analyzer->analyze(tok, Analyzer::Direction::Reverse);
if (result.isModified())
return ChildrenToVisit::done;
return ChildrenToVisit::op1_and_op2;
});
return result;
}
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Analyzer::Action analyzeRange(const Token* start, const Token* end) {
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Analyzer::Action result = Analyzer::Action::None;
for (const Token* tok = start; tok && tok != end; tok = tok->next()) {
Analyzer::Action action = analyzer->analyze(tok, Analyzer::Direction::Reverse);
if (action.isModified())
return action;
result |= action;
}
return result;
}
Token* isDeadCode(Token* tok, const Token* end = nullptr) {
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int opSide = 0;
for (; tok && tok->astParent(); tok = tok->astParent()) {
if (tok == end)
break;
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Token* parent = tok->astParent();
if (Token::simpleMatch(parent, ":")) {
if (astIsLHS(tok))
opSide = 1;
else if (astIsRHS(tok))
opSide = 2;
else
opSide = 0;
}
if (tok != parent->astOperand2())
continue;
if (Token::simpleMatch(parent, ":"))
parent = parent->astParent();
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if (!Token::Match(parent, "%oror%|&&|?"))
continue;
Token* condTok = parent->astOperand1();
if (!condTok)
continue;
bool checkThen, checkElse;
std::tie(checkThen, checkElse) = evalCond(condTok);
if (parent->str() == "?") {
if (checkElse && opSide == 1)
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return parent;
if (checkThen && opSide == 2)
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return parent;
}
if (!checkThen && parent->str() == "&&")
return parent;
if (!checkElse && parent->str() == "||")
return parent;
}
return nullptr;
}
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void traverse(Token* start, const Token* end = nullptr) {
if (start == end)
return;
std::size_t i = start->index();
for (Token* tok = start->previous(); succeeds(tok, end); tok = tok->previous()) {
if (tok->index() >= i)
throw InternalError(tok, "Cyclic reverse analysis.");
i = tok->index();
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if (tok == start || (tok->str() == "{" && (tok->scope()->type == Scope::ScopeType::eFunction ||
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tok->scope()->type == Scope::ScopeType::eLambda))) {
const Function* f = tok->scope()->function;
if (f && f->isConstructor()) {
if (const Token* initList = f->constructorMemberInitialization())
traverse(tok->previous(), tok->tokAt(initList->index() - tok->index()));
}
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break;
}
if (Token::Match(tok, "return|break|continue"))
break;
if (Token::Match(tok, "%name% :"))
break;
if (Token::simpleMatch(tok, ":"))
continue;
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// Evaluate LHS of assignment before RHS
if (Token* assignTok = assignExpr(tok)) {
// If assignTok has broken ast then stop
if (!assignTok->astOperand1() || !assignTok->astOperand2())
break;
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Token* assignTop = assignTok;
bool continueB = true;
while (assignTop->isAssignmentOp()) {
if (!Token::Match(assignTop->astOperand1(), "%assign%")) {
continueB &= updateRecursive(assignTop->astOperand1());
}
if (!assignTop->astParent())
break;
assignTop = assignTop->astParent();
}
// Is assignment in dead code
if (Token* parent = isDeadCode(assignTok)) {
tok = parent;
continue;
}
// Simple assign
if (assignTok->astParent() == assignTop || assignTok == assignTop) {
Analyzer::Action rhsAction =
analyzer->analyze(assignTok->astOperand2(), Analyzer::Direction::Reverse);
Analyzer::Action lhsAction =
analyzer->analyze(assignTok->astOperand1(), Analyzer::Direction::Reverse);
// Assignment from
if (rhsAction.isRead() && !lhsAction.isInvalid() && assignTok->astOperand1()->exprId() > 0) {
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const std::string info = "Assignment from '" + assignTok->expressionString() + "'";
ValuePtr<Analyzer> a = analyzer->reanalyze(assignTok->astOperand1(), info);
if (a) {
valueFlowGenericForward(nextAfterAstRightmostLeaf(assignTok->astOperand2()),
assignTok->astOperand2()->scope()->bodyEnd,
a,
settings);
}
// Assignment to
} else if (lhsAction.matches() && !assignTok->astOperand2()->hasKnownIntValue() &&
assignTok->astOperand2()->exprId() > 0 &&
isConstExpression(assignTok->astOperand2(), settings->library, true)) {
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const std::string info = "Assignment to '" + assignTok->expressionString() + "'";
ValuePtr<Analyzer> a = analyzer->reanalyze(assignTok->astOperand2(), info);
if (a) {
valueFlowGenericForward(nextAfterAstRightmostLeaf(assignTok->astOperand2()),
assignTok->astOperand2()->scope()->bodyEnd,
a,
settings);
valueFlowGenericReverse(assignTok->astOperand1()->previous(), end, a, settings);
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}
}
}
if (!continueB)
break;
if (!updateRecursive(assignTop->astOperand2()))
break;
tok = previousBeforeAstLeftmostLeaf(assignTop)->next();
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continue;
}
if (tok->str() == ")" && !isUnevaluated(tok)) {
if (Token* top = getTopFunction(tok->link())) {
if (!updateRecursive(top))
break;
Token* next = previousBeforeAstLeftmostLeaf(top);
if (next && precedes(next, tok))
tok = next->next();
}
continue;
}
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if (tok->str() == "}") {
Token* condTok = getCondTokFromEnd(tok);
if (!condTok)
break;
Analyzer::Action condAction = analyzeRecursive(condTok);
const bool inLoop = condTok->astTop() && Token::Match(condTok->astTop()->previous(), "for|while (");
// Evaluate condition of for and while loops first
if (inLoop) {
if (Token::findmatch(tok->link(), "goto|break", tok))
break;
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if (condAction.isModified())
break;
valueFlowGenericForward(condTok, analyzer, settings);
}
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Token* thenEnd;
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const bool hasElse = Token::simpleMatch(tok->link()->tokAt(-2), "} else {");
if (hasElse) {
thenEnd = tok->link()->tokAt(-2);
} else {
thenEnd = tok;
}
Analyzer::Action thenAction = analyzeRange(thenEnd->link(), thenEnd);
Analyzer::Action elseAction = Analyzer::Action::None;
if (hasElse) {
elseAction = analyzeRange(tok->link(), tok);
}
if (thenAction.isModified() && inLoop)
break;
else if (thenAction.isModified() && !elseAction.isModified())
analyzer->assume(condTok, hasElse);
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else if (elseAction.isModified() && !thenAction.isModified())
analyzer->assume(condTok, !hasElse);
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// Bail if one of the branches are read to avoid FPs due to over constraints
else if (thenAction.isIdempotent() || elseAction.isIdempotent() || thenAction.isRead() ||
elseAction.isRead())
break;
if (thenAction.isInvalid() || elseAction.isInvalid())
break;
if (!thenAction.isModified() && !elseAction.isModified())
valueFlowGenericForward(condTok, analyzer, settings);
else if (condAction.isRead())
break;
// If the condition modifies the variable then bail
if (condAction.isModified())
break;
tok = condTok->astTop()->previous();
continue;
}
if (tok->str() == "{") {
if (tok->previous() &&
(Token::simpleMatch(tok->previous(), "do") ||
(tok->strAt(-1) == ")" && Token::Match(tok->linkAt(-1)->previous(), "for|while (")))) {
Analyzer::Action action = analyzeRange(tok, tok->link());
if (action.isModified())
break;
}
Token* condTok = getCondTokFromEnd(tok->link());
if (condTok) {
Analyzer::Result r = valueFlowGenericForward(condTok, analyzer, settings);
if (r.action.isModified())
break;
}
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if (Token::simpleMatch(tok->tokAt(-2), "} else {"))
tok = tok->linkAt(-2);
if (Token::simpleMatch(tok->previous(), ") {"))
tok = tok->previous()->link();
continue;
}
if (Token* next = isUnevaluated(tok)) {
tok = next;
continue;
}
if (Token* parent = isDeadCode(tok)) {
tok = parent;
continue;
}
if (tok->str() == "case") {
const Scope* scope = tok->scope();
while (scope && scope->type != Scope::eSwitch)
scope = scope->nestedIn;
if (!scope || scope->type != Scope::eSwitch)
break;
tok = tok->tokAt(scope->bodyStart->index() - tok->index() - 1);
continue;
}
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if (!update(tok))
break;
}
}
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static Token* assignExpr(Token* tok) {
if (Token::Match(tok, ")|}"))
tok = tok->link();
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while (tok->astParent() && (astIsRHS(tok) || !tok->astParent()->isBinaryOp())) {
if (tok->astParent()->isAssignmentOp())
return tok->astParent();
tok = tok->astParent();
}
return nullptr;
}
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static Token* isUnevaluated(Token* tok) {
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if (Token::Match(tok, ")|>") && tok->link()) {
Token* start = tok->link();
if (Token::Match(start->previous(), "sizeof|decltype ("))
return start->previous();
if (Token::simpleMatch(start, "<"))
return start;
}
return nullptr;
}
};
void valueFlowGenericReverse(Token* start, const ValuePtr<Analyzer>& a, const Settings* settings)
{
ReverseTraversal rt{a, settings};
rt.traverse(start);
}
void valueFlowGenericReverse(Token* start, const Token* end, const ValuePtr<Analyzer>& a, const Settings* settings)
{
ReverseTraversal rt{a, settings};
rt.traverse(start, end);
}