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//=======- UncountedLocalVarsChecker.cpp -------------------------*- C++ -*-==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "ASTUtils.h"
#include "DiagOutputUtils.h"
#include "PtrTypesSemantics.h"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/ParentMapContext.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "llvm/ADT/DenseSet.h"
#include <optional>
using namespace clang;
using namespace ento;
namespace {
// for ( int a = ...) ... true
// for ( int a : ...) ... true
// if ( int* a = ) ... true
// anything else ... false
bool isDeclaredInForOrIf(const VarDecl *Var) {
assert(Var);
auto &ASTCtx = Var->getASTContext();
auto parent = ASTCtx.getParents(*Var);
if (parent.size() == 1) {
if (auto *DS = parent.begin()->get<DeclStmt>()) {
DynTypedNodeList grandParent = ASTCtx.getParents(*DS);
if (grandParent.size() == 1) {
return grandParent.begin()->get<ForStmt>() ||
grandParent.begin()->get<IfStmt>() ||
grandParent.begin()->get<CXXForRangeStmt>();
}
}
}
return false;
}
// FIXME: should be defined by anotations in the future
bool isRefcountedStringsHack(const VarDecl *V) {
assert(V);
auto safeClass = [](const std::string &className) {
return className == "String" || className == "AtomString" ||
className == "UniquedString" || className == "Identifier";
};
QualType QT = V->getType();
auto *T = QT.getTypePtr();
if (auto *CXXRD = T->getAsCXXRecordDecl()) {
if (safeClass(safeGetName(CXXRD)))
return true;
}
if (T->isPointerType() || T->isReferenceType()) {
if (auto *CXXRD = T->getPointeeCXXRecordDecl()) {
if (safeClass(safeGetName(CXXRD)))
return true;
}
}
return false;
}
bool isGuardedScopeEmbeddedInGuardianScope(const VarDecl *Guarded,
const VarDecl *MaybeGuardian) {
assert(Guarded);
assert(MaybeGuardian);
if (!MaybeGuardian->isLocalVarDecl())
return false;
const CompoundStmt *guardiansClosestCompStmtAncestor = nullptr;
ASTContext &ctx = MaybeGuardian->getASTContext();
for (DynTypedNodeList guardianAncestors = ctx.getParents(*MaybeGuardian);
!guardianAncestors.empty();
guardianAncestors = ctx.getParents(
*guardianAncestors
.begin()) // FIXME - should we handle all of the parents?
) {
for (auto &guardianAncestor : guardianAncestors) {
if (auto *CStmtParentAncestor = guardianAncestor.get<CompoundStmt>()) {
guardiansClosestCompStmtAncestor = CStmtParentAncestor;
break;
}
}
if (guardiansClosestCompStmtAncestor)
break;
}
if (!guardiansClosestCompStmtAncestor)
return false;
// We need to skip the first CompoundStmt to avoid situation when guardian is
// defined in the same scope as guarded variable.
bool HaveSkippedFirstCompoundStmt = false;
for (DynTypedNodeList guardedVarAncestors = ctx.getParents(*Guarded);
!guardedVarAncestors.empty();
guardedVarAncestors = ctx.getParents(
*guardedVarAncestors
.begin()) // FIXME - should we handle all of the parents?
) {
for (auto &guardedVarAncestor : guardedVarAncestors) {
if (auto *CStmtAncestor = guardedVarAncestor.get<CompoundStmt>()) {
if (!HaveSkippedFirstCompoundStmt) {
HaveSkippedFirstCompoundStmt = true;
continue;
}
if (CStmtAncestor == guardiansClosestCompStmtAncestor)
return true;
}
}
}
return false;
}
class UncountedLocalVarsChecker
: public Checker<check::ASTDecl<TranslationUnitDecl>> {
BugType Bug{this,
"Uncounted raw pointer or reference not provably backed by "
"ref-counted variable",
"WebKit coding guidelines"};
mutable BugReporter *BR;
public:
void checkASTDecl(const TranslationUnitDecl *TUD, AnalysisManager &MGR,
BugReporter &BRArg) const {
BR = &BRArg;
// The calls to checkAST* from AnalysisConsumer don't
// visit template instantiations or lambda classes. We
// want to visit those, so we make our own RecursiveASTVisitor.
struct LocalVisitor : public RecursiveASTVisitor<LocalVisitor> {
const UncountedLocalVarsChecker *Checker;
explicit LocalVisitor(const UncountedLocalVarsChecker *Checker)
: Checker(Checker) {
assert(Checker);
}
bool shouldVisitTemplateInstantiations() const { return true; }
bool shouldVisitImplicitCode() const { return false; }
bool VisitVarDecl(VarDecl *V) {
Checker->visitVarDecl(V);
return true;
}
};
LocalVisitor visitor(this);
visitor.TraverseDecl(const_cast<TranslationUnitDecl *>(TUD));
}
void visitVarDecl(const VarDecl *V) const {
if (shouldSkipVarDecl(V))
return;
const auto *ArgType = V->getType().getTypePtr();
if (!ArgType)
return;
std::optional<bool> IsUncountedPtr = isUncountedPtr(ArgType);
if (IsUncountedPtr && *IsUncountedPtr) {
const Expr *const InitExpr = V->getInit();
if (!InitExpr)
return; // FIXME: later on we might warn on uninitialized vars too
const clang::Expr *const InitArgOrigin =
tryToFindPtrOrigin(InitExpr, /*StopAtFirstRefCountedObj=*/false)
.first;
if (!InitArgOrigin)
return;
if (isa<CXXThisExpr>(InitArgOrigin))
return;
if (auto *Ref = llvm::dyn_cast<DeclRefExpr>(InitArgOrigin)) {
if (auto *MaybeGuardian =
dyn_cast_or_null<VarDecl>(Ref->getFoundDecl())) {
const auto *MaybeGuardianArgType =
MaybeGuardian->getType().getTypePtr();
if (!MaybeGuardianArgType)
return;
const CXXRecordDecl *const MaybeGuardianArgCXXRecord =
MaybeGuardianArgType->getAsCXXRecordDecl();
if (!MaybeGuardianArgCXXRecord)
return;
if (MaybeGuardian->isLocalVarDecl() &&
(isRefCounted(MaybeGuardianArgCXXRecord) ||
isRefcountedStringsHack(MaybeGuardian)) &&
isGuardedScopeEmbeddedInGuardianScope(V, MaybeGuardian)) {
return;
}
// Parameters are guaranteed to be safe for the duration of the call
// by another checker.
if (isa<ParmVarDecl>(MaybeGuardian))
return;
}
}
reportBug(V);
}
}
bool shouldSkipVarDecl(const VarDecl *V) const {
assert(V);
if (!V->isLocalVarDecl())
return true;
if (isDeclaredInForOrIf(V))
return true;
return false;
}
void reportBug(const VarDecl *V) const {
assert(V);
SmallString<100> Buf;
llvm::raw_svector_ostream Os(Buf);
Os << "Local variable ";
printQuotedQualifiedName(Os, V);
Os << " is uncounted and unsafe.";
PathDiagnosticLocation BSLoc(V->getLocation(), BR->getSourceManager());
auto Report = std::make_unique<BasicBugReport>(Bug, Os.str(), BSLoc);
Report->addRange(V->getSourceRange());
BR->emitReport(std::move(Report));
}
};
} // namespace
void ento::registerUncountedLocalVarsChecker(CheckerManager &Mgr) {
Mgr.registerChecker<UncountedLocalVarsChecker>();
}
bool ento::shouldRegisterUncountedLocalVarsChecker(const CheckerManager &) {
return true;
}
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