[clang] 2c6424e - [webkit.UncountedLambdaCapturesChecker] Ignore trivial functions and [[clang::noescape]]. (#114897)
via cfe-commits
cfe-commits at lists.llvm.org
Tue Nov 12 09:46:32 PST 2024
Author: Ryosuke Niwa
Date: 2024-11-12T09:46:28-08:00
New Revision: 2c6424e691e32f79bc303203deb1c91634d62286
URL: https://github.com/llvm/llvm-project/commit/2c6424e691e32f79bc303203deb1c91634d62286
DIFF: https://github.com/llvm/llvm-project/commit/2c6424e691e32f79bc303203deb1c91634d62286.diff
LOG: [webkit.UncountedLambdaCapturesChecker] Ignore trivial functions and [[clang::noescape]]. (#114897)
This PR makes webkit.UncountedLambdaCapturesChecker ignore trivial
functions as well as the one being passed to an argument with
[[clang::noescape]] attribute. This dramatically reduces the false
positive rate for this checker.
To do this, this PR replaces VisitLambdaExpr in favor of checking
lambdas via VisitDeclRefExpr and VisitCallExpr. The idea is that if a
lambda is defined but never called or stored somewhere, then capturing
whatever variable in such a lambda is harmless.
VisitCallExpr explicitly looks for direct invocation of lambdas and
registers its DeclRefExpr to be ignored in VisitDeclRefExpr. If a lambda
is being passed to a function, it checks whether its argument is
annotated with [[clang::noescape]]. If it's not annotated such, it
checks captures for their safety.
Because WTF::switchOn could not be annotated with [[clang::noescape]] as
function type parameters are variadic template function so we hard-code
this function into the checker.
In order to check whether "this" pointer is ref-counted type or not, we
override TraverseDecl and record the most recent method's declaration.
In addition, this PR fixes a bug in isUnsafePtr that it was erroneously
checking whether std::nullopt was returned by isUncounted and
isUnchecked as opposed to the actual boolean value.
Finally, this PR also converts the accompanying test to use -verify and
adds a bunch of tests.
Added:
Modified:
clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.cpp
clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.h
clang/lib/StaticAnalyzer/Checkers/WebKit/UncountedLambdaCapturesChecker.cpp
clang/test/Analysis/Checkers/WebKit/mock-types.h
clang/test/Analysis/Checkers/WebKit/uncounted-lambda-captures.cpp
Removed:
################################################################################
diff --git a/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.cpp b/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.cpp
index 31bebdb07dbdc2..5412fea6f13230 100644
--- a/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.cpp
@@ -222,7 +222,13 @@ std::optional<bool> isUncheckedPtr(const QualType T) {
std::optional<bool> isUnsafePtr(const QualType T) {
if (T->isPointerType() || T->isReferenceType()) {
if (auto *CXXRD = T->getPointeeCXXRecordDecl()) {
- return isUncounted(CXXRD) || isUnchecked(CXXRD);
+ auto isUncountedPtr = isUncounted(CXXRD);
+ auto isUncheckedPtr = isUnchecked(CXXRD);
+ if (isUncountedPtr && isUncheckedPtr)
+ return *isUncountedPtr || *isUncheckedPtr;
+ if (isUncountedPtr)
+ return *isUncountedPtr;
+ return isUncheckedPtr;
}
}
return false;
diff --git a/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.h b/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.h
index 7c6c0a63f22aba..681ea55c613553 100644
--- a/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.h
+++ b/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.h
@@ -75,6 +75,10 @@ std::optional<bool> isUncountedPtr(const clang::QualType T);
/// class, false if not, std::nullopt if inconclusive.
std::optional<bool> isUncheckedPtr(const clang::QualType T);
+/// \returns true if \p T is either a raw pointer or reference to an uncounted
+/// or unchecked class, false if not, std::nullopt if inconclusive.
+std::optional<bool> isUnsafePtr(const QualType T);
+
/// \returns true if \p T is a RefPtr, Ref, CheckedPtr, CheckedRef, or its
/// variant, false if not.
bool isSafePtrType(const clang::QualType T);
diff --git a/clang/lib/StaticAnalyzer/Checkers/WebKit/UncountedLambdaCapturesChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/WebKit/UncountedLambdaCapturesChecker.cpp
index 998bd4ccee07db..914ff6d44270da 100644
--- a/clang/lib/StaticAnalyzer/Checkers/WebKit/UncountedLambdaCapturesChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/WebKit/UncountedLambdaCapturesChecker.cpp
@@ -6,6 +6,7 @@
//
//===----------------------------------------------------------------------===//
+#include "ASTUtils.h"
#include "DiagOutputUtils.h"
#include "PtrTypesSemantics.h"
#include "clang/AST/CXXInheritance.h"
@@ -26,6 +27,7 @@ class UncountedLambdaCapturesChecker
BugType Bug{this, "Lambda capture of uncounted variable",
"WebKit coding guidelines"};
mutable BugReporter *BR = nullptr;
+ TrivialFunctionAnalysis TFA;
public:
void checkASTDecl(const TranslationUnitDecl *TUD, AnalysisManager &MGR,
@@ -37,6 +39,11 @@ class UncountedLambdaCapturesChecker
// want to visit those, so we make our own RecursiveASTVisitor.
struct LocalVisitor : public RecursiveASTVisitor<LocalVisitor> {
const UncountedLambdaCapturesChecker *Checker;
+ llvm::DenseSet<const DeclRefExpr *> DeclRefExprsToIgnore;
+ QualType ClsType;
+
+ using Base = RecursiveASTVisitor<LocalVisitor>;
+
explicit LocalVisitor(const UncountedLambdaCapturesChecker *Checker)
: Checker(Checker) {
assert(Checker);
@@ -45,32 +52,118 @@ class UncountedLambdaCapturesChecker
bool shouldVisitTemplateInstantiations() const { return true; }
bool shouldVisitImplicitCode() const { return false; }
- bool VisitLambdaExpr(LambdaExpr *L) {
- Checker->visitLambdaExpr(L);
+ bool TraverseCXXMethodDecl(CXXMethodDecl *CXXMD) {
+ llvm::SaveAndRestore SavedDecl(ClsType);
+ ClsType = CXXMD->getThisType();
+ return Base::TraverseCXXMethodDecl(CXXMD);
+ }
+
+ bool shouldCheckThis() {
+ auto result = !ClsType.isNull() ? isUnsafePtr(ClsType) : std::nullopt;
+ return result && *result;
+ }
+
+ bool VisitDeclRefExpr(DeclRefExpr *DRE) {
+ if (DeclRefExprsToIgnore.contains(DRE))
+ return true;
+ auto *VD = dyn_cast_or_null<VarDecl>(DRE->getDecl());
+ if (!VD)
+ return true;
+ auto *Init = VD->getInit();
+ if (!Init)
+ return true;
+ auto *L = dyn_cast_or_null<LambdaExpr>(Init->IgnoreParenCasts());
+ if (!L)
+ return true;
+ Checker->visitLambdaExpr(L, shouldCheckThis());
return true;
}
+
+ // WTF::switchOn(T, F... f) is a variadic template function and couldn't
+ // be annotated with NOESCAPE. We hard code it here to workaround that.
+ bool shouldTreatAllArgAsNoEscape(FunctionDecl *Decl) {
+ auto *NsDecl = Decl->getParent();
+ if (!NsDecl || !isa<NamespaceDecl>(NsDecl))
+ return false;
+ return safeGetName(NsDecl) == "WTF" && safeGetName(Decl) == "switchOn";
+ }
+
+ bool VisitCallExpr(CallExpr *CE) {
+ checkCalleeLambda(CE);
+ if (auto *Callee = CE->getDirectCallee()) {
+ bool TreatAllArgsAsNoEscape = shouldTreatAllArgAsNoEscape(Callee);
+ unsigned ArgIndex = 0;
+ for (auto *Param : Callee->parameters()) {
+ if (ArgIndex >= CE->getNumArgs())
+ return true;
+ auto *Arg = CE->getArg(ArgIndex)->IgnoreParenCasts();
+ if (!Param->hasAttr<NoEscapeAttr>() && !TreatAllArgsAsNoEscape) {
+ if (auto *L = dyn_cast_or_null<LambdaExpr>(Arg)) {
+ Checker->visitLambdaExpr(L, shouldCheckThis());
+ }
+ }
+ ++ArgIndex;
+ }
+ }
+ return true;
+ }
+
+ void checkCalleeLambda(CallExpr *CE) {
+ auto *Callee = CE->getCallee();
+ if (!Callee)
+ return;
+ auto *DRE = dyn_cast<DeclRefExpr>(Callee->IgnoreParenCasts());
+ if (!DRE)
+ return;
+ auto *MD = dyn_cast_or_null<CXXMethodDecl>(DRE->getDecl());
+ if (!MD || CE->getNumArgs() != 1)
+ return;
+ auto *Arg = CE->getArg(0)->IgnoreParenCasts();
+ auto *ArgRef = dyn_cast<DeclRefExpr>(Arg);
+ if (!ArgRef)
+ return;
+ auto *VD = dyn_cast_or_null<VarDecl>(ArgRef->getDecl());
+ if (!VD)
+ return;
+ auto *Init = VD->getInit();
+ if (!Init)
+ return;
+ auto *L = dyn_cast_or_null<LambdaExpr>(Init->IgnoreParenCasts());
+ if (!L)
+ return;
+ DeclRefExprsToIgnore.insert(ArgRef);
+ Checker->visitLambdaExpr(L, shouldCheckThis(),
+ /* ignoreParamVarDecl */ true);
+ }
};
LocalVisitor visitor(this);
visitor.TraverseDecl(const_cast<TranslationUnitDecl *>(TUD));
}
- void visitLambdaExpr(LambdaExpr *L) const {
+ void visitLambdaExpr(LambdaExpr *L, bool shouldCheckThis,
+ bool ignoreParamVarDecl = false) const {
+ if (TFA.isTrivial(L->getBody()))
+ return;
for (const LambdaCapture &C : L->captures()) {
if (C.capturesVariable()) {
ValueDecl *CapturedVar = C.getCapturedVar();
+ if (ignoreParamVarDecl && isa<ParmVarDecl>(CapturedVar))
+ continue;
QualType CapturedVarQualType = CapturedVar->getType();
- if (auto *CapturedVarType = CapturedVarQualType.getTypePtrOrNull()) {
- auto IsUncountedPtr = isUncountedPtr(CapturedVarQualType);
- if (IsUncountedPtr && *IsUncountedPtr)
- reportBug(C, CapturedVar, CapturedVarType);
- }
+ auto IsUncountedPtr = isUnsafePtr(CapturedVar->getType());
+ if (IsUncountedPtr && *IsUncountedPtr)
+ reportBug(C, CapturedVar, CapturedVarQualType);
+ } else if (C.capturesThis() && shouldCheckThis) {
+ if (ignoreParamVarDecl) // this is always a parameter to this function.
+ continue;
+ reportBugOnThisPtr(C);
}
}
}
void reportBug(const LambdaCapture &Capture, ValueDecl *CapturedVar,
- const Type *T) const {
+ const QualType T) const {
assert(CapturedVar);
SmallString<100> Buf;
@@ -89,7 +182,25 @@ class UncountedLambdaCapturesChecker
}
printQuotedQualifiedName(Os, Capture.getCapturedVar());
- Os << " to uncounted type is unsafe.";
+ Os << " to ref-counted type or CheckedPtr-capable type is unsafe.";
+
+ PathDiagnosticLocation BSLoc(Capture.getLocation(), BR->getSourceManager());
+ auto Report = std::make_unique<BasicBugReport>(Bug, Os.str(), BSLoc);
+ BR->emitReport(std::move(Report));
+ }
+
+ void reportBugOnThisPtr(const LambdaCapture &Capture) const {
+ SmallString<100> Buf;
+ llvm::raw_svector_ostream Os(Buf);
+
+ if (Capture.isExplicit()) {
+ Os << "Captured ";
+ } else {
+ Os << "Implicitly captured ";
+ }
+
+ Os << "raw-pointer 'this' to ref-counted type or CheckedPtr-capable type "
+ "is unsafe.";
PathDiagnosticLocation BSLoc(Capture.getLocation(), BR->getSourceManager());
auto Report = std::make_unique<BasicBugReport>(Bug, Os.str(), BSLoc);
diff --git a/clang/test/Analysis/Checkers/WebKit/mock-types.h b/clang/test/Analysis/Checkers/WebKit/mock-types.h
index 9c9326f0f11cfb..4a55ddab64d804 100644
--- a/clang/test/Analysis/Checkers/WebKit/mock-types.h
+++ b/clang/test/Analysis/Checkers/WebKit/mock-types.h
@@ -135,7 +135,9 @@ struct RefCountable {
void ref() {}
void deref() {}
void method();
+ void constMethod() const;
int trivial() { return 123; }
+ RefCountable* next();
};
template <typename T> T *downcast(T *t) { return t; }
diff --git a/clang/test/Analysis/Checkers/WebKit/uncounted-lambda-captures.cpp b/clang/test/Analysis/Checkers/WebKit/uncounted-lambda-captures.cpp
index 27e0a74d583cd3..9bfcdea04755d2 100644
--- a/clang/test/Analysis/Checkers/WebKit/uncounted-lambda-captures.cpp
+++ b/clang/test/Analysis/Checkers/WebKit/uncounted-lambda-captures.cpp
@@ -1,39 +1,71 @@
-// RUN: %clang_analyze_cc1 -analyzer-checker=webkit.UncountedLambdaCapturesChecker %s 2>&1 | FileCheck %s --strict-whitespace
-#include "mock-types.h"
+// RUN: %clang_analyze_cc1 -analyzer-checker=webkit.UncountedLambdaCapturesChecker -verify %s
+
+struct RefCountable {
+ void ref() {}
+ void deref() {}
+ void method();
+ void constMethod() const;
+ int trivial() { return 123; }
+ RefCountable* next();
+};
+
+RefCountable* make_obj();
+
+void someFunction();
+template <typename Callback> void call(Callback callback) {
+ someFunction();
+ callback();
+}
void raw_ptr() {
- RefCountable* ref_countable = nullptr;
- auto foo1 = [ref_countable](){};
- // CHECK: warning: Captured raw-pointer 'ref_countable' to uncounted type is unsafe [webkit.UncountedLambdaCapturesChecker]
- // CHECK-NEXT:{{^ 6 | }} auto foo1 = [ref_countable](){};
- // CHECK-NEXT:{{^ | }} ^
- auto foo2 = [&ref_countable](){};
- // CHECK: warning: Captured raw-pointer 'ref_countable' to uncounted type is unsafe [webkit.UncountedLambdaCapturesChecker]
- auto foo3 = [&](){ ref_countable = nullptr; };
- // CHECK: warning: Implicitly captured raw-pointer 'ref_countable' to uncounted type is unsafe [webkit.UncountedLambdaCapturesChecker]
- // CHECK-NEXT:{{^ 12 | }} auto foo3 = [&](){ ref_countable = nullptr; };
- // CHECK-NEXT:{{^ | }} ^
- auto foo4 = [=](){ (void) ref_countable; };
- // CHECK: warning: Implicitly captured raw-pointer 'ref_countable' to uncounted type is unsafe [webkit.UncountedLambdaCapturesChecker]
+ RefCountable* ref_countable = make_obj();
+ auto foo1 = [ref_countable](){
+ // expected-warning at -1{{Captured raw-pointer 'ref_countable' to ref-counted type or CheckedPtr-capable type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
+ ref_countable->method();
+ };
+ auto foo2 = [&ref_countable](){
+ // expected-warning at -1{{Captured raw-pointer 'ref_countable' to ref-counted type or CheckedPtr-capable type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
+ ref_countable->method();
+ };
+ auto foo3 = [&](){
+ ref_countable->method();
+ // expected-warning at -1{{Implicitly captured raw-pointer 'ref_countable' to ref-counted type or CheckedPtr-capable type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
+ ref_countable = nullptr;
+ };
+
+ auto foo4 = [=](){
+ ref_countable->method();
+ // expected-warning at -1{{Implicitly captured raw-pointer 'ref_countable' to ref-counted type or CheckedPtr-capable type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
+ };
+
+ call(foo1);
+ call(foo2);
+ call(foo3);
+ call(foo4);
// Confirm that the checker respects [[clang::suppress]].
RefCountable* suppressed_ref_countable = nullptr;
[[clang::suppress]] auto foo5 = [suppressed_ref_countable](){};
- // CHECK-NOT: warning: Captured raw-pointer 'suppressed_ref_countable' to uncounted type is unsafe [webkit.UncountedLambdaCapturesChecker]
+ // no warning.
+ call(foo5);
}
void references() {
RefCountable automatic;
RefCountable& ref_countable_ref = automatic;
+ auto foo1 = [ref_countable_ref](){ ref_countable_ref.constMethod(); };
+ // expected-warning at -1{{Captured reference 'ref_countable_ref' to ref-counted type or CheckedPtr-capable type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
+ auto foo2 = [&ref_countable_ref](){ ref_countable_ref.method(); };
+ // expected-warning at -1{{Captured reference 'ref_countable_ref' to ref-counted type or CheckedPtr-capable type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
+ auto foo3 = [&](){ ref_countable_ref.method(); };
+ // expected-warning at -1{{Implicitly captured reference 'ref_countable_ref' to ref-counted type or CheckedPtr-capable type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
+ auto foo4 = [=](){ ref_countable_ref.constMethod(); };
+ // expected-warning at -1{{Implicitly captured reference 'ref_countable_ref' to ref-counted type or CheckedPtr-capable type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
- auto foo1 = [ref_countable_ref](){};
- // CHECK: warning: Captured reference 'ref_countable_ref' to uncounted type is unsafe [webkit.UncountedLambdaCapturesChecker]
- auto foo2 = [&ref_countable_ref](){};
- // CHECK: warning: Captured reference 'ref_countable_ref' to uncounted type is unsafe [webkit.UncountedLambdaCapturesChecker]
- auto foo3 = [&](){ (void) ref_countable_ref; };
- // CHECK: warning: Implicitly captured reference 'ref_countable_ref' to uncounted type is unsafe [webkit.UncountedLambdaCapturesChecker]
- auto foo4 = [=](){ (void) ref_countable_ref; };
- // CHECK: warning: Implicitly captured reference 'ref_countable_ref' to uncounted type is unsafe [webkit.UncountedLambdaCapturesChecker]
+ call(foo1);
+ call(foo2);
+ call(foo3);
+ call(foo4);
}
void quiet() {
@@ -45,5 +77,100 @@ void quiet() {
auto foo3 = [&]() {};
auto foo4 = [=]() {};
+
+ call(foo3);
+ call(foo4);
+
RefCountable *ref_countable = nullptr;
}
+
+template <typename Callback>
+void map(RefCountable* start, [[clang::noescape]] Callback&& callback)
+{
+ while (start) {
+ callback(*start);
+ start = start->next();
+ }
+}
+
+template <typename Callback1, typename Callback2>
+void doubleMap(RefCountable* start, [[clang::noescape]] Callback1&& callback1, Callback2&& callback2)
+{
+ while (start) {
+ callback1(*start);
+ callback2(*start);
+ start = start->next();
+ }
+}
+
+void noescape_lambda() {
+ RefCountable* someObj = make_obj();
+ RefCountable* otherObj = make_obj();
+ map(make_obj(), [&](RefCountable& obj) {
+ otherObj->method();
+ });
+ doubleMap(make_obj(), [&](RefCountable& obj) {
+ otherObj->method();
+ }, [&](RefCountable& obj) {
+ otherObj->method();
+ // expected-warning at -1{{Implicitly captured raw-pointer 'otherObj' to ref-counted type or CheckedPtr-capable type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
+ });
+ ([&] {
+ someObj->method();
+ })();
+}
+
+void lambda_capture_param(RefCountable* obj) {
+ auto someLambda = [&] {
+ obj->method();
+ };
+ someLambda();
+ someLambda();
+}
+
+struct RefCountableWithLambdaCapturingThis {
+ void ref() const;
+ void deref() const;
+ void nonTrivial();
+
+ void method_captures_this_safe() {
+ auto lambda = [&]() {
+ nonTrivial();
+ };
+ lambda();
+ }
+
+ void method_captures_this_unsafe() {
+ auto lambda = [&]() {
+ nonTrivial();
+ // expected-warning at -1{{Implicitly captured raw-pointer 'this' to ref-counted type or CheckedPtr-capable type is unsafe [webkit.UncountedLambdaCapturesChecker]}}
+ };
+ call(lambda);
+ }
+};
+
+struct NonRefCountableWithLambdaCapturingThis {
+ void nonTrivial();
+
+ void method_captures_this_safe() {
+ auto lambda = [&]() {
+ nonTrivial();
+ };
+ lambda();
+ }
+
+ void method_captures_this_unsafe() {
+ auto lambda = [&]() {
+ nonTrivial();
+ };
+ call(lambda);
+ }
+};
+
+void trivial_lambda() {
+ RefCountable* ref_countable = make_obj();
+ auto trivial_lambda = [&]() {
+ return ref_countable->trivial();
+ };
+ trivial_lambda();
+}
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