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forwardanalyzer.cpp
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695 lines (651 loc) · 28.6 KB
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#include "forwardanalyzer.h"
#include "analyzer.h"
#include "astutils.h"
#include "settings.h"
#include "symboldatabase.h"
#include "token.h"
#include "valueptr.h"
#include <algorithm>
#include <functional>
struct ForwardTraversal {
enum class Progress { Continue, Break, Skip };
enum class Terminate { None, Bail, Escape, Modified, Inconclusive, Conditional };
ForwardTraversal(const ValuePtr<Analyzer>& analyzer, const Settings* settings)
: analyzer(analyzer), settings(settings), actions(Analyzer::Action::None), analyzeOnly(false), analyzeTerminate(false)
{}
ValuePtr<Analyzer> analyzer;
const Settings* settings;
Analyzer::Action actions;
bool analyzeOnly;
bool analyzeTerminate;
Terminate terminate = Terminate::None;
Progress Break(Terminate t = Terminate::None) {
if ((!analyzeOnly || analyzeTerminate) && t != Terminate::None)
terminate = t;
return Progress::Break;
}
struct Branch {
Analyzer::Action action = Analyzer::Action::None;
bool check = false;
bool escape = false;
bool escapeUnknown = false;
const Token* endBlock = nullptr;
bool isEscape() const {
return escape || escapeUnknown;
}
bool isConclusiveEscape() const {
return escape && !escapeUnknown;
}
bool isModified() const {
return action.isModified() && !isConclusiveEscape();
}
bool isInconclusive() const {
return action.isInconclusive() && !isConclusiveEscape();
}
bool isDead() const {
return action.isModified() || action.isInconclusive() || isEscape();
}
};
bool stopUpdates() {
analyzeOnly = true;
return actions.isModified();
}
std::pair<bool, bool> evalCond(const Token* tok) {
std::vector<int> result = analyzer->evaluate(tok);
// TODO: We should convert to bool
bool checkThen = std::any_of(result.begin(), result.end(), [](int x) {
return x == 1;
});
bool checkElse = std::any_of(result.begin(), result.end(), [](int x) {
return x == 0;
});
return std::make_pair(checkThen, checkElse);
}
template<class T, REQUIRES("T must be a Token class", std::is_convertible<T*, const Token*>)>
Progress traverseTok(T* tok, std::function<Progress(T*)> f, bool traverseUnknown, T** out = nullptr) {
if (Token::Match(tok, "asm|goto|continue|setjmp|longjmp"))
return Break();
else if (Token::Match(tok, "return|throw") || isEscapeFunction(tok, &settings->library)) {
traverseRecursive(tok->astOperand1(), f, traverseUnknown);
traverseRecursive(tok->astOperand2(), f, traverseUnknown);
return Break(Terminate::Escape);
} else if (isUnevaluated(tok)) {
if (out)
*out = tok->link();
return Progress::Skip;
} else if (tok->astOperand1() && tok->astOperand2() && Token::Match(tok, "?|&&|%oror%")) {
if (traverseConditional(tok, f, traverseUnknown) == Progress::Break)
return Break();
if (out)
*out = nextAfterAstRightmostLeaf(tok);
return Progress::Skip;
// Skip lambdas
} else if (T* lambdaEndToken = findLambdaEndToken(tok)) {
if (checkScope(lambdaEndToken).isModified())
return Break(Terminate::Bail);
if (out)
*out = lambdaEndToken->next();
// Skip class scope
} else if (tok->str() == "{" && tok->scope() && tok->scope()->isClassOrStruct()) {
if (out)
*out = tok->link();
} else {
if (f(tok) == Progress::Break)
return Break();
}
return Progress::Continue;
}
template<class T, REQUIRES("T must be a Token class", std::is_convertible<T*, const Token*>)>
Progress traverseRecursive(T* tok, std::function<Progress(T*)> f, bool traverseUnknown, unsigned int recursion=0) {
if (!tok)
return Progress::Continue;
if (recursion > 10000)
return Progress::Skip;
T* firstOp = tok->astOperand1();
T* secondOp = tok->astOperand2();
// Evaluate:
// 1. RHS of assignment before LHS
// 2. Unary op before operand
if (tok->isAssignmentOp() || !secondOp)
std::swap(firstOp, secondOp);
if (firstOp && traverseRecursive(firstOp, f, traverseUnknown, recursion+1) == Progress::Break)
return Break();
Progress p = tok->isAssignmentOp() ? Progress::Continue : traverseTok(tok, f, traverseUnknown);
if (p == Progress::Break)
return Break();
if (p == Progress::Continue && secondOp && traverseRecursive(secondOp, f, traverseUnknown, recursion+1) == Progress::Break)
return Break();
if (tok->isAssignmentOp() && traverseTok(tok, f, traverseUnknown) == Progress::Break)
return Break();
return Progress::Continue;
}
template<class T, class F, REQUIRES("T must be a Token class", std::is_convertible<T*, const Token*>)>
Progress traverseConditional(T* tok, F f, bool traverseUnknown) {
if (Token::Match(tok, "?|&&|%oror%") && tok->astOperand1() && tok->astOperand2()) {
T* condTok = tok->astOperand1();
T* childTok = tok->astOperand2();
bool checkThen, checkElse;
std::tie(checkThen, checkElse) = evalCond(condTok);
if (!checkThen && !checkElse) {
// Stop if the value is conditional
if (!traverseUnknown && analyzer->isConditional() && stopUpdates()) {
return Break(Terminate::Conditional);
}
checkThen = true;
checkElse = true;
}
if (childTok->str() == ":") {
if (checkThen && traverseRecursive(childTok->astOperand1(), f, traverseUnknown) == Progress::Break)
return Break();
if (checkElse && traverseRecursive(childTok->astOperand2(), f, traverseUnknown) == Progress::Break)
return Break();
} else {
if (!checkThen && tok->str() == "&&")
return Progress::Continue;
if (!checkElse && tok->str() == "||")
return Progress::Continue;
if (traverseRecursive(childTok, f, traverseUnknown) == Progress::Break)
return Break();
}
}
return Progress::Continue;
}
Progress update(Token* tok) {
Analyzer::Action action = analyzer->analyze(tok, Analyzer::Direction::Forward);
actions |= action;
if (!action.isNone() && !analyzeOnly)
analyzer->update(tok, action, Analyzer::Direction::Forward);
if (action.isInconclusive() && !analyzer->lowerToInconclusive())
return Break(Terminate::Inconclusive);
if (action.isInvalid())
return Break(Terminate::Modified);
if (action.isWrite() && !action.isRead())
// Analysis of this write will continue separately
return Break(Terminate::Modified);
return Progress::Continue;
}
Progress updateTok(Token* tok, Token** out = nullptr) {
std::function<Progress(Token*)> f = [this](Token* tok2) {
return update(tok2);
};
return traverseTok(tok, f, false, out);
}
Progress updateRecursive(Token* tok) {
std::function<Progress(Token*)> f = [this](Token* tok2) {
return update(tok2);
};
return traverseRecursive(tok, f, false);
}
template <class T>
T* findRange(T* start, const Token* end, std::function<bool(Analyzer::Action)> pred) {
for (T* tok = start; tok && tok != end; tok = tok->next()) {
Analyzer::Action action = analyzer->analyze(tok, Analyzer::Direction::Forward);
if (pred(action))
return tok;
}
return nullptr;
}
Analyzer::Action analyzeRecursive(const Token* start) {
Analyzer::Action result = Analyzer::Action::None;
std::function<Progress(const Token*)> f = [&](const Token* tok) {
result = analyzer->analyze(tok, Analyzer::Direction::Forward);
if (result.isModified() || result.isInconclusive())
return Break();
return Progress::Continue;
};
traverseRecursive(start, f, true);
return result;
}
Analyzer::Action analyzeRange(const Token* start, const Token* end) {
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::Forward);
if (action.isModified() || action.isInconclusive())
return action;
result |= action;
}
return result;
}
void forkRange(Token* start, const Token* end) {
ForwardTraversal ft = *this;
ft.updateRange(start, end);
}
ForwardTraversal forkScope(Token* endBlock, bool analyze = false) const {
ForwardTraversal ft = *this;
ft.analyzer->forkScope(endBlock);
if (analyze) {
ft.analyzeOnly = true;
ft.analyzeTerminate = true;
}
ft.updateRange(endBlock->link(), endBlock);
return ft;
}
std::vector<ForwardTraversal> tryForkScope(Token* endBlock, bool isModified = false) {
if (analyzer->updateScope(endBlock, isModified)) {
ForwardTraversal ft = forkScope(endBlock);
return {ft};
}
return std::vector<ForwardTraversal> {};
}
static bool hasGoto(const Token* endBlock) {
return Token::findsimplematch(endBlock->link(), "goto", endBlock);
}
bool hasInnerReturnScope(const Token* start, const Token* end) const {
for (const Token* tok=start; tok != end; tok = tok->previous()) {
if (Token::simpleMatch(tok, "}")) {
const Token* ftok = nullptr;
bool r = isReturnScope(tok, &settings->library, &ftok);
if (r)
return true;
}
}
return false;
}
bool isEscapeScope(const Token* endBlock, bool& unknown) {
const Token* ftok = nullptr;
bool r = isReturnScope(endBlock, &settings->library, &ftok);
if (!r && ftok)
unknown = true;
return r;
}
enum class Status {
None,
Escaped,
Modified,
Inconclusive,
};
Analyzer::Action analyzeScope(const Token* endBlock) {
return analyzeRange(endBlock->link(), endBlock);
}
Analyzer::Action checkScope(Token* endBlock) {
Analyzer::Action a = analyzeScope(endBlock);
tryForkScope(endBlock, a.isModified());
return a;
}
Analyzer::Action checkScope(const Token* endBlock) {
Analyzer::Action a = analyzeScope(endBlock);
return a;
}
bool checkBranch(Branch& branch, Token* endBlock) {
Analyzer::Action a = analyzeScope(endBlock);
branch.action = a;
std::vector<ForwardTraversal> ft1 = tryForkScope(endBlock, a.isModified());
bool bail = hasGoto(endBlock);
if (!a.isModified() && !bail) {
if (ft1.empty()) {
// Traverse into the branch to see if there is a conditional escape
if (!branch.escape && hasInnerReturnScope(endBlock->previous(), endBlock->link())) {
ForwardTraversal ft2 = forkScope(endBlock, true);
if (ft2.terminate == Terminate::Escape) {
branch.escape = true;
branch.escapeUnknown = false;
}
}
} else {
if (ft1.front().terminate == Terminate::Escape) {
branch.escape = true;
branch.escapeUnknown = false;
}
}
}
return bail;
}
void continueUpdateRangeAfterLoop(std::vector<ForwardTraversal>& ftv, Token* start, const Token* endToken) {
for (ForwardTraversal& ft : ftv) {
// If analysis has terminated normally, then continue analysis
if (ft.terminate == Terminate::None)
ft.updateRange(start, endToken);
}
}
Progress updateLoop(const Token* endToken,
Token* endBlock,
Token* condTok,
Token* initTok = nullptr,
Token* stepTok = nullptr) {
const bool isDoWhile = precedes(endBlock, condTok);
const bool alwaysEnterLoop = !condTok || (condTok->hasKnownIntValue() && condTok->values().front().intvalue != 0);
Analyzer::Action bodyAnalysis = analyzeScope(endBlock);
Analyzer::Action allAnalysis = bodyAnalysis;
if (condTok)
allAnalysis |= analyzeRecursive(condTok);
if (initTok)
allAnalysis |= analyzeRecursive(initTok);
if (stepTok)
allAnalysis |= analyzeRecursive(stepTok);
actions |= allAnalysis;
if (allAnalysis.isInconclusive()) {
if (!analyzer->lowerToInconclusive())
return Break(Terminate::Bail);
} else if (allAnalysis.isModified()) {
if (!analyzer->lowerToPossible())
return Break(Terminate::Bail);
}
// Traverse condition after lowering
if (condTok && (!isDoWhile || (!bodyAnalysis.isModified() && !bodyAnalysis.isIdempotent()))) {
if (updateRecursive(condTok) == Progress::Break)
return Break();
bool checkThen = true;
bool checkElse = false;
std::tie(checkThen, checkElse) = evalCond(condTok);
// condition is false, we don't enter the loop
if (checkElse)
return Progress::Continue;
}
if (allAnalysis.isModified() && alwaysEnterLoop)
return Break(Terminate::Bail);
std::vector<ForwardTraversal> ftv = tryForkScope(endBlock, allAnalysis.isModified());
if (bodyAnalysis.isModified()) {
Token* writeTok = findRange(endBlock->link(), endBlock, std::mem_fn(&Analyzer::Action::isModified));
const Token* nextStatement = Token::findmatch(writeTok, ";|}", endBlock);
if (!Token::Match(nextStatement, ";|} break ;")) {
if (!allAnalysis.isIncremental())
continueUpdateRangeAfterLoop(ftv, endBlock, endToken);
return Break(Terminate::Bail);
}
} else {
if (stepTok && updateRecursive(stepTok) == Progress::Break) {
if (!allAnalysis.isIncremental())
continueUpdateRangeAfterLoop(ftv, endBlock, endToken);
return Break(Terminate::Bail);
}
}
// TODO: Should we traverse the body?
// updateRange(endBlock->link(), endBlock);
return Progress::Continue;
}
Progress updateRange(Token* start, const Token* end, int depth = 20) {
if (depth < 0)
return Break(Terminate::Bail);
std::size_t i = 0;
for (Token* tok = start; tok && tok != end; tok = tok->next()) {
Token* next = nullptr;
if (tok->index() <= i)
throw InternalError(tok, "Cyclic forward analysis.");
i = tok->index();
if (tok->link()) {
// Skip casts..
if (tok->str() == "(" && !tok->astOperand2() && tok->isCast()) {
tok = tok->link();
continue;
}
// Skip template arguments..
if (tok->str() == "<") {
tok = tok->link();
continue;
}
}
// Evaluate RHS of assignment before LHS
if (Token* assignTok = assignExpr(tok)) {
if (updateRecursive(assignTok) == Progress::Break)
return Break();
tok = nextAfterAstRightmostLeaf(assignTok);
if (!tok)
return Break();
} else if (tok->str() == "break") {
const Token *scopeEndToken = findNextTokenFromBreak(tok);
if (!scopeEndToken)
return Break();
tok = skipTo(tok, scopeEndToken, end);
if (!analyzer->lowerToPossible())
return Break(Terminate::Bail);
// TODO: Don't break, instead move to the outer scope
if (!tok)
return Break();
} else if (Token::Match(tok, "%name% :") || tok->str() == "case") {
if (!analyzer->lowerToPossible())
return Break(Terminate::Bail);
} else if (tok->link() && tok->str() == "}") {
const Scope* scope = tok->scope();
if (!scope)
return Break();
if (Token::Match(tok->link()->previous(), ")|else {")) {
const Token* tok2 = tok->link()->previous();
const bool inElse = Token::simpleMatch(tok2, "else {");
const bool inLoop = inElse ? false : Token::Match(tok2->link()->previous(), "while|for (");
Token* condTok = getCondTokFromEnd(tok);
if (!condTok)
return Break();
if (!condTok->hasKnownIntValue() || inLoop) {
if (!analyzer->lowerToPossible())
return Break(Terminate::Bail);
} else if (condTok->values().front().intvalue == inElse) {
return Break();
}
// Handle for loop
Token* stepTok = getStepTokFromEnd(tok);
bool checkThen, checkElse;
std::tie(checkThen, checkElse) = evalCond(condTok);
if (stepTok && !checkElse) {
if (updateRecursive(stepTok) == Progress::Break)
return Break();
if (updateRecursive(condTok) == Progress::Break)
return Break();
}
analyzer->assume(condTok, !inElse, tok);
if (Token::simpleMatch(tok, "} else {"))
tok = tok->linkAt(2);
} else if (scope->type == Scope::eTry) {
if (!analyzer->lowerToPossible())
return Break(Terminate::Bail);
} else if (scope->type == Scope::eLambda) {
return Break();
} else if (scope->type == Scope::eDo && Token::simpleMatch(tok, "} while (")) {
if (updateLoop(end, tok, tok->tokAt(2)->astOperand2()) == Progress::Break)
return Break();
tok = tok->linkAt(2);
} else if (Token::simpleMatch(tok->next(), "else {")) {
tok = tok->linkAt(2);
}
} else if (tok->isControlFlowKeyword() && Token::Match(tok, "if|while|for (") && Token::simpleMatch(tok->next()->link(), ") {")) {
Token* endCond = tok->next()->link();
Token* endBlock = endCond->next()->link();
Token* condTok = getCondTok(tok);
Token* initTok = getInitTok(tok);
if (initTok && updateRecursive(initTok) == Progress::Break)
return Break();
if (Token::Match(tok, "for|while (")) {
// For-range loop
if (Token::simpleMatch(condTok, ":")) {
Token* conTok = condTok->astOperand2();
if (conTok && updateRecursive(conTok) == Progress::Break)
return Break();
if (updateLoop(end, endBlock, condTok) == Progress::Break)
return Break();
} else {
Token* stepTok = getStepTok(tok);
if (updateLoop(end, endBlock, condTok, initTok, stepTok) == Progress::Break)
return Break();
}
tok = endBlock;
} else {
// Traverse condition
if (updateRecursive(condTok) == Progress::Break)
return Break();
Branch thenBranch{};
Branch elseBranch{};
// Check if condition is true or false
std::tie(thenBranch.check, elseBranch.check) = evalCond(condTok);
bool hasElse = Token::simpleMatch(endBlock, "} else {");
bool bail = false;
// Traverse then block
thenBranch.escape = isEscapeScope(endBlock, thenBranch.escapeUnknown);
if (thenBranch.check) {
if (updateRange(endCond->next(), endBlock, depth - 1) == Progress::Break)
return Break();
} else if (!elseBranch.check) {
if (checkBranch(thenBranch, endBlock))
bail = true;
}
// Traverse else block
if (hasElse) {
elseBranch.escape = isEscapeScope(endBlock->linkAt(2), elseBranch.escapeUnknown);
if (elseBranch.check) {
Progress result = updateRange(endBlock->tokAt(2), endBlock->linkAt(2), depth - 1);
if (result == Progress::Break)
return Break();
} else if (!thenBranch.check) {
if (checkBranch(elseBranch, endBlock->linkAt(2)))
bail = true;
}
tok = endBlock->linkAt(2);
} else {
tok = endBlock;
}
actions |= (thenBranch.action | elseBranch.action);
if (bail)
return Break();
if (thenBranch.isDead() && elseBranch.isDead()) {
if (thenBranch.isModified() && elseBranch.isModified())
return Break(Terminate::Modified);
if (thenBranch.isConclusiveEscape() && elseBranch.isConclusiveEscape())
return Break(Terminate::Escape);
return Break(Terminate::Bail);
}
// Conditional return
if (thenBranch.isEscape() && !hasElse) {
if (!thenBranch.isConclusiveEscape()) {
if (!analyzer->lowerToInconclusive())
return Break(Terminate::Bail);
} else if (thenBranch.check) {
return Break();
} else {
if (analyzer->isConditional() && stopUpdates())
return Break(Terminate::Conditional);
analyzer->assume(condTok, false);
}
}
if (thenBranch.isInconclusive() || elseBranch.isInconclusive()) {
if (!analyzer->lowerToInconclusive())
return Break(Terminate::Bail);
} else if (thenBranch.isModified() || elseBranch.isModified()) {
if (!hasElse && analyzer->isConditional() && stopUpdates())
return Break(Terminate::Conditional);
if (!analyzer->lowerToPossible())
return Break(Terminate::Bail);
analyzer->assume(condTok, elseBranch.isModified());
}
}
} else if (Token::simpleMatch(tok, "try {")) {
Token* endBlock = tok->next()->link();
Analyzer::Action a = analyzeScope(endBlock);
if (updateRange(tok->next(), endBlock, depth - 1) == Progress::Break)
return Break();
if (a.isModified())
analyzer->lowerToPossible();
tok = endBlock;
} else if (Token::simpleMatch(tok, "do {")) {
Token* endBlock = tok->next()->link();
Token* condTok = Token::simpleMatch(endBlock, "} while (") ? endBlock->tokAt(2)->astOperand2() : nullptr;
if (updateLoop(end, endBlock, condTok) == Progress::Break)
return Break();
if (condTok)
tok = endBlock->linkAt(2)->next();
else
tok = endBlock;
} else if (Token::Match(tok, "assert|ASSERT (")) {
const Token* condTok = tok->next()->astOperand2();
bool checkThen, checkElse;
std::tie(checkThen, checkElse) = evalCond(condTok);
if (checkElse)
return Break();
if (!checkThen)
analyzer->assume(condTok, true, tok);
} else if (Token::simpleMatch(tok, "switch (")) {
if (updateRecursive(tok->next()->astOperand2()) == Progress::Break)
return Break();
return Break();
} else {
if (updateTok(tok, &next) == Progress::Break)
return Break();
if (next) {
if (precedes(next, end))
tok = next->previous();
else
return Break();
}
}
// Prevent infinite recursion
if (tok->next() == start)
break;
}
return Progress::Continue;
}
static bool isUnevaluated(const Token* tok) {
if (Token::Match(tok->previous(), "sizeof|decltype ("))
return true;
return false;
}
static Token* assignExpr(Token* tok) {
while (tok->astParent() && astIsLHS(tok)) {
if (tok->astParent()->isAssignmentOp())
return tok->astParent();
tok = tok->astParent();
}
return nullptr;
}
static Token* skipTo(Token* tok, const Token* dest, const Token* end = nullptr) {
if (end && dest->index() > end->index())
return nullptr;
int i = dest->index() - tok->index();
if (i > 0)
return tok->tokAt(dest->index() - tok->index());
return nullptr;
}
static bool isConditional(const Token* tok) {
const Token* parent = tok->astParent();
while (parent && !Token::Match(parent, "%oror%|&&|:")) {
tok = parent;
parent = parent->astParent();
}
return parent && (parent->str() == ":" || parent->astOperand2() == tok);
}
static Token* getInitTok(Token* tok) {
if (!tok)
return nullptr;
if (Token::Match(tok, "%name% ("))
return getInitTok(tok->next());
if (tok->str() != "(")
return nullptr;
if (!Token::simpleMatch(tok->astOperand2(), ";"))
return nullptr;
if (Token::simpleMatch(tok->astOperand2()->astOperand1(), ";"))
return nullptr;
return tok->astOperand2()->astOperand1();
}
static Token* getStepTok(Token* tok) {
if (!tok)
return nullptr;
if (Token::Match(tok, "%name% ("))
return getStepTok(tok->next());
if (tok->str() != "(")
return nullptr;
if (!Token::simpleMatch(tok->astOperand2(), ";"))
return nullptr;
if (!Token::simpleMatch(tok->astOperand2()->astOperand2(), ";"))
return nullptr;
return tok->astOperand2()->astOperand2()->astOperand2();
}
static Token* getStepTokFromEnd(Token* tok) {
if (!Token::simpleMatch(tok, "}"))
return nullptr;
Token* end = tok->link()->previous();
if (!Token::simpleMatch(end, ")"))
return nullptr;
return getStepTok(end->link());
}
};
Analyzer::Action valueFlowGenericForward(Token* start,
const Token* end,
const ValuePtr<Analyzer>& a,
const Settings* settings)
{
ForwardTraversal ft{a, settings};
ft.updateRange(start, end);
return ft.actions;
}
Analyzer::Action valueFlowGenericForward(Token* start, const ValuePtr<Analyzer>& a, const Settings* settings)
{
ForwardTraversal ft{a, settings};
ft.updateRecursive(start);
return ft.actions;
}