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[webkit.UncountedLambdaCapturesChecker] Add the support for WTF::ScopeExit and WTF::makeVisitor #161926

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Merged
rniwa merged 3 commits into from
Oct 24, 2025
Merged

[webkit.UncountedLambdaCapturesChecker] Add the support for WTF::ScopeExit and WTF::makeVisitor #161926

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6c6dd96
[webkit.UncountedLambdaCapturesChecker] Add the support for WTF::Scop…
rniwa Oct 4, 2025
97deb83
Fix formatting.
rniwa Oct 4, 2025
1ed0c4c
Split the code to detect WTF::visit/std::visit as isVisitFunction
rniwa Oct 24, 2025
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95 changes: 87 additions & 8 deletions clang/lib/StaticAnalyzer/Checkers/WebKit/RawPtrRefLambdaCapturesChecker.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,9 @@ class RawPtrRefLambdaCapturesChecker
llvm::DenseSet<const DeclRefExpr *> DeclRefExprsToIgnore;
llvm::DenseSet<const LambdaExpr *> LambdasToIgnore;
llvm::DenseSet<const ValueDecl *> ProtectedThisDecls;
llvm::DenseSet<const CallExpr *> CallToIgnore;
llvm::DenseSet<const CXXConstructExpr *> ConstructToIgnore;
llvm::DenseMap<const VarDecl *, const LambdaExpr *> LambdaOwnerMap;

QualType ClsType;

Expand Down Expand Up @@ -101,10 +103,60 @@ class RawPtrRefLambdaCapturesChecker
auto *Init = VD->getInit();
if (!Init)
return true;
auto *L = dyn_cast_or_null<LambdaExpr>(Init->IgnoreParenCasts());
if (!L)
if (auto *L = dyn_cast_or_null<LambdaExpr>(Init->IgnoreParenCasts())) {
LambdasToIgnore.insert(L); // Evaluate lambdas in VisitDeclRefExpr.
return true;
}
if (!VD->hasLocalStorage())
return true;
LambdasToIgnore.insert(L); // Evaluate lambdas in VisitDeclRefExpr.
if (auto *E = dyn_cast<ExprWithCleanups>(Init))
Init = E->getSubExpr();
if (auto *E = dyn_cast<CXXBindTemporaryExpr>(Init))
Init = E->getSubExpr();
if (auto *CE = dyn_cast<CallExpr>(Init)) {
if (auto *Callee = CE->getDirectCallee()) {
auto FnName = safeGetName(Callee);
unsigned ArgCnt = CE->getNumArgs();
if (FnName == "makeScopeExit" && ArgCnt == 1) {
auto *Arg = CE->getArg(0);
if (auto *E = dyn_cast<MaterializeTemporaryExpr>(Arg))
Arg = E->getSubExpr();
if (auto *L = dyn_cast<LambdaExpr>(Arg)) {
LambdaOwnerMap.insert(std::make_pair(VD, L));
CallToIgnore.insert(CE);
LambdasToIgnore.insert(L);
}
} else if (FnName == "makeVisitor") {
for (unsigned ArgIndex = 0; ArgIndex < ArgCnt; ++ArgIndex) {
auto *Arg = CE->getArg(ArgIndex);
if (auto *E = dyn_cast<MaterializeTemporaryExpr>(Arg))
Arg = E->getSubExpr();
if (auto *L = dyn_cast<LambdaExpr>(Arg)) {
LambdaOwnerMap.insert(std::make_pair(VD, L));
CallToIgnore.insert(CE);
LambdasToIgnore.insert(L);
}
}
}
}
} else if (auto *CE = dyn_cast<CXXConstructExpr>(Init)) {
if (auto *Ctor = CE->getConstructor()) {
if (auto *Cls = Ctor->getParent()) {
auto FnName = safeGetName(Cls);
unsigned ArgCnt = CE->getNumArgs();
if (FnName == "ScopeExit" && ArgCnt == 1) {
auto *Arg = CE->getArg(0);
if (auto *E = dyn_cast<MaterializeTemporaryExpr>(Arg))
Arg = E->getSubExpr();
if (auto *L = dyn_cast<LambdaExpr>(Arg)) {
LambdaOwnerMap.insert(std::make_pair(VD, L));
ConstructToIgnore.insert(CE);
LambdasToIgnore.insert(L);
}
}
}
}
}
return true;
}

Expand All @@ -114,6 +166,12 @@ class RawPtrRefLambdaCapturesChecker
auto *VD = dyn_cast_or_null<VarDecl>(DRE->getDecl());
if (!VD)
return true;
if (auto It = LambdaOwnerMap.find(VD); It != LambdaOwnerMap.end()) {
auto *L = It->second;
Checker->visitLambdaExpr(L, shouldCheckThis() && !hasProtectedThis(L),
ClsType);
return true;
}
auto *Init = VD->getInit();
if (!Init)
return true;
Expand Down Expand Up @@ -167,10 +225,30 @@ class RawPtrRefLambdaCapturesChecker
}

bool VisitCallExpr(CallExpr *CE) override {
if (CallToIgnore.contains(CE))
return true;
checkCalleeLambda(CE);
if (auto *Callee = CE->getDirectCallee())
if (auto *Callee = CE->getDirectCallee()) {
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@t-rasmud t-rasmud Oct 23, 2025

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Optional Nit: Modify the code to use early returns.

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@rniwa rniwa Oct 24, 2025

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I don't think we can quite convert to early returns since we to handle else-if case when getDirectCallee returns nullptr. But I'd extract a helper function isVisitFunction so that more early returns could be used inside there.

if (auto *Ns = Callee->getParent()) {
auto NsName = safeGetName(Ns);
bool IsVisitFn = safeGetName(Callee) == "visit";
bool ArgCnt = CE->getNumArgs();
if (IsVisitFn && ArgCnt && (NsName == "WTF" || NsName == "std")) {
if (auto *Arg = CE->getArg(0)) {
Arg = Arg->IgnoreParenCasts();
if (auto *DRE = dyn_cast<DeclRefExpr>(Arg)) {
if (auto *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
if (LambdaOwnerMap.contains(VD)) {
DeclRefExprsToIgnore.insert(DRE);
return true;
}
}
}
}
}
}
checkParameters(CE, Callee);
else if (auto *CalleeE = CE->getCallee()) {
} else if (auto *CalleeE = CE->getCallee()) {
if (auto *DRE = dyn_cast<DeclRefExpr>(CalleeE->IgnoreParenCasts())) {
if (auto *Callee = dyn_cast_or_null<FunctionDecl>(DRE->getDecl()))
checkParameters(CE, Callee);
Expand Down Expand Up @@ -280,7 +358,7 @@ class RawPtrRefLambdaCapturesChecker
LambdasToIgnore.insert(L);
}

bool hasProtectedThis(LambdaExpr *L) {
bool hasProtectedThis(const LambdaExpr *L) {
for (const LambdaCapture &OtherCapture : L->captures()) {
if (!OtherCapture.capturesVariable())
continue;
Expand Down Expand Up @@ -378,7 +456,8 @@ class RawPtrRefLambdaCapturesChecker
visitor.TraverseDecl(const_cast<TranslationUnitDecl *>(TUD));
}

void visitLambdaExpr(LambdaExpr *L, bool shouldCheckThis, const QualType T,
void visitLambdaExpr(const LambdaExpr *L, bool shouldCheckThis,
const QualType T,
bool ignoreParamVarDecl = false) const {
if (TFA.isTrivial(L->getBody()))
return;
Expand Down Expand Up @@ -410,7 +489,7 @@ class RawPtrRefLambdaCapturesChecker
}

void reportBug(const LambdaCapture &Capture, ValueDecl *CapturedVar,
const QualType T, LambdaExpr *L) const {
const QualType T, const LambdaExpr *L) const {
assert(CapturedVar);

auto Location = Capture.getLocation();
Expand Down
151 changes: 151 additions & 0 deletions clang/test/Analysis/Checkers/WebKit/uncounted-lambda-captures.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -107,6 +107,79 @@ class HashMap {
ValueType* m_table { nullptr };
};

class ScopeExit final {
public:
template<typename ExitFunctionParameter>
explicit ScopeExit(ExitFunctionParameter&& exitFunction)
: m_exitFunction(std::move(exitFunction)) {
}

ScopeExit(ScopeExit&& other)
: m_exitFunction(std::move(other.m_exitFunction))
, m_execute(std::move(other.m_execute)) {
}

~ScopeExit() {
if (m_execute)
m_exitFunction();
}

WTF::Function<void()> take() {
m_execute = false;
return std::move(m_exitFunction);
}

void release() { m_execute = false; }

ScopeExit(const ScopeExit&) = delete;
ScopeExit& operator=(const ScopeExit&) = delete;
ScopeExit& operator=(ScopeExit&&) = delete;

private:
WTF::Function<void()> m_exitFunction;
bool m_execute { true };
};

template<typename ExitFunction> ScopeExit makeScopeExit(ExitFunction&&);
template<typename ExitFunction>
ScopeExit makeScopeExit(ExitFunction&& exitFunction)
{
return ScopeExit(std::move(exitFunction));
}

// Visitor adapted from http://stackoverflow.com/questions/25338795/is-there-a-name-for-this-tuple-creation-idiom

template<class A, class... B> struct Visitor : Visitor<A>, Visitor<B...> {
Visitor(A a, B... b)
: Visitor<A>(a)
, Visitor<B...>(b...)
{
}

using Visitor<A>::operator ();
using Visitor<B...>::operator ();
};

template<class A> struct Visitor<A> : A {
Visitor(A a)
: A(a)
{
}

using A::operator();
};

template<class... F> Visitor<F...> makeVisitor(F... f)
{
return Visitor<F...>(f...);
}

void opaqueFunction();
template <typename Visitor, typename... Variants> void visit(Visitor&& v, Variants&&... values)
{
opaqueFunction();
}

} // namespace WTF

struct A {
Expand Down Expand Up @@ -501,3 +574,81 @@ void RefCountedObj::call() const
};
callLambda(lambda);
}

void scope_exit(RefCountable* obj) {
auto scope = WTF::makeScopeExit([&] {
obj->method();
});
someFunction();
WTF::ScopeExit scope2([&] {
obj->method();
});
someFunction();
}

void doWhateverWith(WTF::ScopeExit& obj);

void scope_exit_with_side_effect(RefCountable* obj) {
auto scope = WTF::makeScopeExit([&] {
obj->method();
// expected-warning@-1{{Implicitly captured raw-pointer 'obj' to uncounted type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
});
doWhateverWith(scope);
}

void scope_exit_static(RefCountable* obj) {
static auto scope = WTF::makeScopeExit([&] {
obj->method();
// expected-warning@-1{{Implicitly captured raw-pointer 'obj' to uncounted type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
});
}

WTF::Function<void()> scope_exit_take_lambda(RefCountable* obj) {
auto scope = WTF::makeScopeExit([&] {
obj->method();
// expected-warning@-1{{Implicitly captured raw-pointer 'obj' to uncounted type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
});
return scope.take();
}

// FIXME: Ideally, we treat release() as a trivial function.
void scope_exit_release(RefCountable* obj) {
auto scope = WTF::makeScopeExit([&] {
obj->method();
// expected-warning@-1{{Implicitly captured raw-pointer 'obj' to uncounted type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
});
scope.release();
}

void make_visitor(RefCountable* obj) {
auto visitor = WTF::makeVisitor([&] {
obj->method();
});
}

void use_visitor(RefCountable* obj) {
auto visitor = WTF::makeVisitor([&] {
obj->method();
});
WTF::visit(visitor, obj);
}

template <typename Visitor, typename ObjectType>
void bad_visit(Visitor&, ObjectType*) {
someFunction();
}

void static_visitor(RefCountable* obj) {
static auto visitor = WTF::makeVisitor([&] {
obj->method();
// expected-warning@-1{{Implicitly captured raw-pointer 'obj' to uncounted type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
});
}

void bad_use_visitor(RefCountable* obj) {
auto visitor = WTF::makeVisitor([&] {
obj->method();
// expected-warning@-1{{Implicitly captured raw-pointer 'obj' to uncounted type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
});
bad_visit(visitor, obj);
}