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[webkit.UncountedLambdaCapturesChecker] Support [[clang::noescape]] on a constructor #126869

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Merged
merged 1 commit into from
Feb 14, 2025
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[webkit.UncountedLambdaCapturesChecker] Support [[clang::noescape]] on a constructor #126869

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26 changes: 25 additions & 1 deletion clang/lib/StaticAnalyzer/Checkers/WebKit/UncountedLambdaCapturesChecker.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,7 @@ class UncountedLambdaCapturesChecker
const UncountedLambdaCapturesChecker *Checker;
llvm::DenseSet<const DeclRefExpr *> DeclRefExprsToIgnore;
llvm::DenseSet<const LambdaExpr *> LambdasToIgnore;
llvm::DenseSet<const CXXConstructExpr *> ConstructToIgnore;
QualType ClsType;

explicit LocalVisitor(const UncountedLambdaCapturesChecker *Checker)
Expand Down Expand Up @@ -106,6 +107,26 @@ class UncountedLambdaCapturesChecker
return safeGetName(NsDecl) == "WTF" && safeGetName(Decl) == "switchOn";
}

bool VisitCXXConstructExpr(CXXConstructExpr *CE) override {
if (ConstructToIgnore.contains(CE))
return true;
if (auto *Callee = CE->getConstructor()) {
unsigned ArgIndex = 0;
for (auto *Param : Callee->parameters()) {
if (ArgIndex >= CE->getNumArgs())
return true;
auto *Arg = CE->getArg(ArgIndex)->IgnoreParenCasts();
if (auto *L = findLambdaInArg(Arg)) {
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@t-rasmud t-rasmud Feb 14, 2025

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For my understanding: Is the LambdaExpr not covered in VisitLambdaExpr? What's special about the expression being an argument to a constructor?

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@rniwa rniwa Feb 14, 2025 •
edited
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Oh, so we wanna ignore lambda expressions that are passed to [[clang::noescape]] argument. The code in VisitCallExpr and now VisitCXXConstructExpr is there to detect this specific case, and then ignore the argument.

LambdasToIgnore.insert(L);
if (!Param->hasAttr<NoEscapeAttr>())
Checker->visitLambdaExpr(L, shouldCheckThis());
}
++ArgIndex;
}
}
return true;
}

bool VisitCallExpr(CallExpr *CE) override {
checkCalleeLambda(CE);
if (auto *Callee = CE->getDirectCallee()) {
Expand Down Expand Up @@ -143,8 +164,10 @@ class UncountedLambdaCapturesChecker
auto *CtorArg = CE->getArg(0)->IgnoreParenCasts();
if (!CtorArg)
return nullptr;
if (auto *Lambda = dyn_cast<LambdaExpr>(CtorArg))
if (auto *Lambda = dyn_cast<LambdaExpr>(CtorArg)) {
ConstructToIgnore.insert(CE);
return Lambda;
}
auto *DRE = dyn_cast<DeclRefExpr>(CtorArg);
if (!DRE)
return nullptr;
Expand All @@ -157,6 +180,7 @@ class UncountedLambdaCapturesChecker
TempExpr = dyn_cast<CXXBindTemporaryExpr>(Init->IgnoreParenCasts());
if (!TempExpr)
return nullptr;
ConstructToIgnore.insert(CE);
return dyn_cast_or_null<LambdaExpr>(TempExpr->getSubExpr());
}

Expand Down
4 changes: 4 additions & 0 deletions clang/test/Analysis/Checkers/WebKit/uncounted-lambda-captures.cpp
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Expand Up @@ -298,7 +298,11 @@ struct RefCountableWithLambdaCapturingThis {
callLambda([&]() -> RefPtr<RefCountable> {
return obj->next();
});
WTF::HashMap<int, RefPtr<RefCountable>> anotherMap([&] {
return obj->next();
});
}

};

struct NonRefCountableWithLambdaCapturingThis {
Expand Down