src/llvm-project/clang/lib/Analysis/FlowSensitive/DataflowAnalysisContext.cpp - toolchain/rustc - Git at Google

 //===-- DataflowAnalysisContext.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
 //
 //===----------------------------------------------------------------------===//
 //
 //  This file defines a DataflowAnalysisContext class that owns objects that
 //  encompass the state of a program and stores context that is used during
 //  dataflow analysis.
 //
 //===----------------------------------------------------------------------===//

 #include "clang/Analysis/FlowSensitive/DataflowAnalysisContext.h"
 #include "clang/AST/ExprCXX.h"
 #include "clang/Analysis/FlowSensitive/DebugSupport.h"
 #include "clang/Analysis/FlowSensitive/Formula.h"
 #include "clang/Analysis/FlowSensitive/Logger.h"
 #include "clang/Analysis/FlowSensitive/Value.h"
 #include "llvm/ADT/SetOperations.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cassert>
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>

 static llvm::cl::opt<std::string> DataflowLog(
     "dataflow-log", llvm::cl::Hidden, llvm::cl::ValueOptional,
     llvm::cl::desc("Emit log of dataflow analysis. With no arg, writes textual "
                    "log to stderr. With an arg, writes HTML logs under the "
                    "specified directory (one per analyzed function)."));

 namespace clang {
 namespace dataflow {

 FieldSet DataflowAnalysisContext::getModeledFields(QualType Type) {
   // During context-sensitive analysis, a struct may be allocated in one
   // function, but its field accessed in a function lower in the stack than
   // the allocation. Since we only collect fields used in the function where
   // the allocation occurs, we can't apply that filter when performing
   // context-sensitive analysis. But, this only applies to storage locations,
   // since field access it not allowed to fail. In contrast, field *values*
   // don't need this allowance, since the API allows for uninitialized fields.
   if (Opts.ContextSensitiveOpts)
     return getObjectFields(Type);

   return llvm::set_intersection(getObjectFields(Type), ModeledFields);
 }

 void DataflowAnalysisContext::addModeledFields(const FieldSet &Fields) {
   ModeledFields.set_union(Fields);
 }

 StorageLocation &DataflowAnalysisContext::createStorageLocation(QualType Type) {
   if (!Type.isNull() && Type->isRecordType()) {
     llvm::DenseMap<const ValueDecl *, StorageLocation *> FieldLocs;
     for (const FieldDecl *Field : getModeledFields(Type))
       if (Field->getType()->isReferenceType())
         FieldLocs.insert({Field, nullptr});
       else
         FieldLocs.insert({Field, &createStorageLocation(
                                      Field->getType().getNonReferenceType())});
     return arena().create<AggregateStorageLocation>(Type, std::move(FieldLocs));
   }
   return arena().create<ScalarStorageLocation>(Type);
 }

 StorageLocation &
 DataflowAnalysisContext::getStableStorageLocation(const VarDecl &D) {
   if (auto *Loc = getStorageLocation(D))
     return *Loc;
   auto &Loc = createStorageLocation(D.getType().getNonReferenceType());
   setStorageLocation(D, Loc);
   return Loc;
 }

 StorageLocation &
 DataflowAnalysisContext::getStableStorageLocation(const Expr &E) {
   if (auto *Loc = getStorageLocation(E))
     return *Loc;
   auto &Loc = createStorageLocation(E.getType());
   setStorageLocation(E, Loc);
   return Loc;
 }

 PointerValue &
 DataflowAnalysisContext::getOrCreateNullPointerValue(QualType PointeeType) {
   auto CanonicalPointeeType =
       PointeeType.isNull() ? PointeeType : PointeeType.getCanonicalType();
   auto Res = NullPointerVals.try_emplace(CanonicalPointeeType, nullptr);
   if (Res.second) {
     auto &PointeeLoc = createStorageLocation(CanonicalPointeeType);
     Res.first->second = &arena().create<PointerValue>(PointeeLoc);
   }
   return *Res.first->second;
 }

 void DataflowAnalysisContext::addFlowConditionConstraint(
     Atom Token, const Formula &Constraint) {
   auto Res = FlowConditionConstraints.try_emplace(Token, &Constraint);
   if (!Res.second) {
     Res.first->second =
         &arena().makeAnd(*Res.first->second, Constraint);
   }
 }

 Atom DataflowAnalysisContext::forkFlowCondition(Atom Token) {
   Atom ForkToken = arena().makeFlowConditionToken();
   FlowConditionDeps[ForkToken].insert(Token);
   addFlowConditionConstraint(ForkToken, arena().makeAtomRef(Token));
   return ForkToken;
 }

 Atom
 DataflowAnalysisContext::joinFlowConditions(Atom FirstToken,
                                             Atom SecondToken) {
   Atom Token = arena().makeFlowConditionToken();
   FlowConditionDeps[Token].insert(FirstToken);
   FlowConditionDeps[Token].insert(SecondToken);
   addFlowConditionConstraint(Token,
                              arena().makeOr(arena().makeAtomRef(FirstToken),
                                             arena().makeAtomRef(SecondToken)));
   return Token;
 }

 Solver::Result DataflowAnalysisContext::querySolver(
     llvm::SetVector<const Formula *> Constraints) {
   Constraints.insert(&arena().makeLiteral(true));
   Constraints.insert(&arena().makeNot(arena().makeLiteral(false)));
   return S->solve(Constraints.getArrayRef());
 }

 bool DataflowAnalysisContext::flowConditionImplies(Atom Token,
                                                    const Formula &Val) {
   // Returns true if and only if truth assignment of the flow condition implies
   // that `Val` is also true. We prove whether or not this property holds by
   // reducing the problem to satisfiability checking. In other words, we attempt
   // to show that assuming `Val` is false makes the constraints induced by the
   // flow condition unsatisfiable.
   llvm::SetVector<const Formula *> Constraints;
   Constraints.insert(&arena().makeAtomRef(Token));
   Constraints.insert(&arena().makeNot(Val));
   llvm::DenseSet<Atom> VisitedTokens;
   addTransitiveFlowConditionConstraints(Token, Constraints, VisitedTokens);
   return isUnsatisfiable(std::move(Constraints));
 }

 bool DataflowAnalysisContext::flowConditionIsTautology(Atom Token) {
   // Returns true if and only if we cannot prove that the flow condition can
   // ever be false.
   llvm::SetVector<const Formula *> Constraints;
   Constraints.insert(&arena().makeNot(arena().makeAtomRef(Token)));
   llvm::DenseSet<Atom> VisitedTokens;
   addTransitiveFlowConditionConstraints(Token, Constraints, VisitedTokens);
   return isUnsatisfiable(std::move(Constraints));
 }

 bool DataflowAnalysisContext::equivalentFormulas(const Formula &Val1,
                                                  const Formula &Val2) {
   llvm::SetVector<const Formula *> Constraints;
   Constraints.insert(&arena().makeNot(arena().makeEquals(Val1, Val2)));
   return isUnsatisfiable(std::move(Constraints));
 }

 void DataflowAnalysisContext::addTransitiveFlowConditionConstraints(
     Atom Token, llvm::SetVector<const Formula *> &Constraints,
     llvm::DenseSet<Atom> &VisitedTokens) {
   auto Res = VisitedTokens.insert(Token);
   if (!Res.second)
     return;

   auto ConstraintsIt = FlowConditionConstraints.find(Token);
   if (ConstraintsIt == FlowConditionConstraints.end()) {
     Constraints.insert(&arena().makeAtomRef(Token));
   } else {
     // Bind flow condition token via `iff` to its set of constraints:
     // FC <=> (C1 ^ C2 ^ ...), where Ci are constraints
     Constraints.insert(&arena().makeEquals(arena().makeAtomRef(Token),
                                            *ConstraintsIt->second));
   }

   auto DepsIt = FlowConditionDeps.find(Token);
   if (DepsIt != FlowConditionDeps.end()) {
     for (Atom DepToken : DepsIt->second) {
       addTransitiveFlowConditionConstraints(DepToken, Constraints,
                                             VisitedTokens);
     }
   }
 }

 void DataflowAnalysisContext::dumpFlowCondition(Atom Token,
                                                 llvm::raw_ostream &OS) {
   llvm::SetVector<const Formula *> Constraints;
   Constraints.insert(&arena().makeAtomRef(Token));
   llvm::DenseSet<Atom> VisitedTokens;
   addTransitiveFlowConditionConstraints(Token, Constraints, VisitedTokens);

   // TODO: have formulas know about true/false directly instead
   Atom True = arena().makeLiteral(true).getAtom();
   Atom False = arena().makeLiteral(false).getAtom();
   Formula::AtomNames Names = {{False, "false"}, {True, "true"}};

   for (const auto *Constraint : Constraints) {
     Constraint->print(OS, &Names);
     OS << "\n";
   }
 }

 const ControlFlowContext *
 DataflowAnalysisContext::getControlFlowContext(const FunctionDecl *F) {
   // Canonicalize the key:
   F = F->getDefinition();
   if (F == nullptr)
     return nullptr;
   auto It = FunctionContexts.find(F);
   if (It != FunctionContexts.end())
     return &It->second;

   if (F->hasBody()) {
     auto CFCtx = ControlFlowContext::build(*F);
     // FIXME: Handle errors.
     assert(CFCtx);
     auto Result = FunctionContexts.insert({F, std::move(*CFCtx)});
     return &Result.first->second;
   }

   return nullptr;
 }

 static std::unique_ptr<Logger> makeLoggerFromCommandLine() {
   if (DataflowLog.empty())
     return Logger::textual(llvm::errs());

   llvm::StringRef Dir = DataflowLog;
   if (auto EC = llvm::sys::fs::create_directories(Dir))
     llvm::errs() << "Failed to create log dir: " << EC.message() << "\n";
   // All analysis runs within a process will log to the same directory.
   // Share a counter so they don't all overwrite each other's 0.html.
   // (Don't share a logger, it's not threadsafe).
   static std::atomic<unsigned> Counter = {0};
   auto StreamFactory =
       [Dir(Dir.str())]() mutable -> std::unique_ptr<llvm::raw_ostream> {
     llvm::SmallString<256> File(Dir);
     llvm::sys::path::append(File,
                             std::to_string(Counter.fetch_add(1)) + ".html");
     std::error_code EC;
     auto OS = std::make_unique<llvm::raw_fd_ostream>(File, EC);
     if (EC) {
       llvm::errs() << "Failed to create log " << File << ": " << EC.message()
                    << "\n";
       return std::make_unique<llvm::raw_null_ostream>();
     }
     return OS;
   };
   return Logger::html(std::move(StreamFactory));
 }

 DataflowAnalysisContext::DataflowAnalysisContext(std::unique_ptr<Solver> S,
                                                  Options Opts)
     : S(std::move(S)), A(std::make_unique<Arena>()), Opts(Opts) {
   assert(this->S != nullptr);
   // If the -dataflow-log command-line flag was set, synthesize a logger.
   // This is ugly but provides a uniform method for ad-hoc debugging dataflow-
   // based tools.
   if (Opts.Log == nullptr) {
     if (DataflowLog.getNumOccurrences() > 0) {
       LogOwner = makeLoggerFromCommandLine();
       this->Opts.Log = LogOwner.get();
       // FIXME: if the flag is given a value, write an HTML log to a file.
     } else {
       this->Opts.Log = &Logger::null();
     }
   }
 }

 DataflowAnalysisContext::~DataflowAnalysisContext() = default;

 } // namespace dataflow
 } // namespace clang

 using namespace clang;

 const Expr &clang::dataflow::ignoreCFGOmittedNodes(const Expr &E) {
   const Expr *Current = &E;
   if (auto *EWC = dyn_cast<ExprWithCleanups>(Current)) {
     Current = EWC->getSubExpr();
     assert(Current != nullptr);
   }
   Current = Current->IgnoreParens();
   assert(Current != nullptr);
   return *Current;
 }

 const Stmt &clang::dataflow::ignoreCFGOmittedNodes(const Stmt &S) {
   if (auto *E = dyn_cast<Expr>(&S))
     return ignoreCFGOmittedNodes(*E);
   return S;
 }

 // FIXME: Does not precisely handle non-virtual diamond inheritance. A single
 // field decl will be modeled for all instances of the inherited field.
 static void getFieldsFromClassHierarchy(QualType Type,
                                         clang::dataflow::FieldSet &Fields) {
   if (Type->isIncompleteType() || Type->isDependentType() ||
       !Type->isRecordType())
     return;

   for (const FieldDecl *Field : Type->getAsRecordDecl()->fields())
     Fields.insert(Field);
   if (auto *CXXRecord = Type->getAsCXXRecordDecl())
     for (const CXXBaseSpecifier &Base : CXXRecord->bases())
       getFieldsFromClassHierarchy(Base.getType(), Fields);
 }

 /// Gets the set of all fields in the type.
 clang::dataflow::FieldSet clang::dataflow::getObjectFields(QualType Type) {
   FieldSet Fields;
   getFieldsFromClassHierarchy(Type, Fields);
   return Fields;
 }
	//===-- DataflowAnalysisContext.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
	//
	//===----------------------------------------------------------------------===//
	//
	// This file defines a DataflowAnalysisContext class that owns objects that
	// encompass the state of a program and stores context that is used during
	// dataflow analysis.
	//
	//===----------------------------------------------------------------------===//

	#include "clang/Analysis/FlowSensitive/DataflowAnalysisContext.h"
	#include "clang/AST/ExprCXX.h"
	#include "clang/Analysis/FlowSensitive/DebugSupport.h"
	#include "clang/Analysis/FlowSensitive/Formula.h"
	#include "clang/Analysis/FlowSensitive/Logger.h"
	#include "clang/Analysis/FlowSensitive/Value.h"
	#include "llvm/ADT/SetOperations.h"
	#include "llvm/ADT/SetVector.h"
	#include "llvm/Support/CommandLine.h"
	#include "llvm/Support/Debug.h"
	#include "llvm/Support/FileSystem.h"
	#include "llvm/Support/Path.h"
	#include "llvm/Support/raw_ostream.h"
	#include <cassert>
	#include <memory>
	#include <string>
	#include <utility>
	#include <vector>

	static llvm::cl::opt<std::string> DataflowLog(
	"dataflow-log", llvm::cl::Hidden, llvm::cl::ValueOptional,
	llvm::cl::desc("Emit log of dataflow analysis. With no arg, writes textual "
	"log to stderr. With an arg, writes HTML logs under the "
	"specified directory (one per analyzed function)."));

	namespace clang {
	namespace dataflow {

	FieldSet DataflowAnalysisContext::getModeledFields(QualType Type) {
	// During context-sensitive analysis, a struct may be allocated in one
	// function, but its field accessed in a function lower in the stack than
	// the allocation. Since we only collect fields used in the function where
	// the allocation occurs, we can't apply that filter when performing
	// context-sensitive analysis. But, this only applies to storage locations,
	// since field access it not allowed to fail. In contrast, field values
	// don't need this allowance, since the API allows for uninitialized fields.
	if (Opts.ContextSensitiveOpts)
	return getObjectFields(Type);

	return llvm::set_intersection(getObjectFields(Type), ModeledFields);
	}

	void DataflowAnalysisContext::addModeledFields(const FieldSet &Fields) {
	ModeledFields.set_union(Fields);
	}

	StorageLocation &DataflowAnalysisContext::createStorageLocation(QualType Type) {
	if (!Type.isNull() && Type->isRecordType()) {
	llvm::DenseMap<const ValueDecl , StorageLocation > FieldLocs;
	for (const FieldDecl *Field : getModeledFields(Type))
	if (Field->getType()->isReferenceType())
	FieldLocs.insert({Field, nullptr});
	else
	FieldLocs.insert({Field, &createStorageLocation(
	Field->getType().getNonReferenceType())});
	return arena().create<AggregateStorageLocation>(Type, std::move(FieldLocs));
	}
	return arena().create<ScalarStorageLocation>(Type);
	}

	StorageLocation &
	DataflowAnalysisContext::getStableStorageLocation(const VarDecl &D) {
	if (auto *Loc = getStorageLocation(D))
	return *Loc;
	auto &Loc = createStorageLocation(D.getType().getNonReferenceType());
	setStorageLocation(D, Loc);
	return Loc;
	}

	StorageLocation &
	DataflowAnalysisContext::getStableStorageLocation(const Expr &E) {
	if (auto *Loc = getStorageLocation(E))
	return *Loc;
	auto &Loc = createStorageLocation(E.getType());
	setStorageLocation(E, Loc);
	return Loc;
	}

	PointerValue &
	DataflowAnalysisContext::getOrCreateNullPointerValue(QualType PointeeType) {
	auto CanonicalPointeeType =
	PointeeType.isNull() ? PointeeType : PointeeType.getCanonicalType();
	auto Res = NullPointerVals.try_emplace(CanonicalPointeeType, nullptr);
	if (Res.second) {
	auto &PointeeLoc = createStorageLocation(CanonicalPointeeType);
	Res.first->second = &arena().create<PointerValue>(PointeeLoc);
	}
	return *Res.first->second;
	}

	void DataflowAnalysisContext::addFlowConditionConstraint(
	Atom Token, const Formula &Constraint) {
	auto Res = FlowConditionConstraints.try_emplace(Token, &Constraint);
	if (!Res.second) {
	Res.first->second =
	&arena().makeAnd(*Res.first->second, Constraint);
	}
	}

	Atom DataflowAnalysisContext::forkFlowCondition(Atom Token) {
	Atom ForkToken = arena().makeFlowConditionToken();
	FlowConditionDeps[ForkToken].insert(Token);
	addFlowConditionConstraint(ForkToken, arena().makeAtomRef(Token));
	return ForkToken;
	}

	Atom
	DataflowAnalysisContext::joinFlowConditions(Atom FirstToken,
	Atom SecondToken) {
	Atom Token = arena().makeFlowConditionToken();
	FlowConditionDeps[Token].insert(FirstToken);
	FlowConditionDeps[Token].insert(SecondToken);
	addFlowConditionConstraint(Token,
	arena().makeOr(arena().makeAtomRef(FirstToken),
	arena().makeAtomRef(SecondToken)));
	return Token;
	}

	Solver::Result DataflowAnalysisContext::querySolver(
	llvm::SetVector<const Formula *> Constraints) {
	Constraints.insert(&arena().makeLiteral(true));
	Constraints.insert(&arena().makeNot(arena().makeLiteral(false)));
	return S->solve(Constraints.getArrayRef());
	}

	bool DataflowAnalysisContext::flowConditionImplies(Atom Token,
	const Formula &Val) {
	// Returns true if and only if truth assignment of the flow condition implies
	// that `Val` is also true. We prove whether or not this property holds by
	// reducing the problem to satisfiability checking. In other words, we attempt
	// to show that assuming `Val` is false makes the constraints induced by the
	// flow condition unsatisfiable.
	llvm::SetVector<const Formula *> Constraints;
	Constraints.insert(&arena().makeAtomRef(Token));
	Constraints.insert(&arena().makeNot(Val));
	llvm::DenseSet<Atom> VisitedTokens;
	addTransitiveFlowConditionConstraints(Token, Constraints, VisitedTokens);
	return isUnsatisfiable(std::move(Constraints));
	}

	bool DataflowAnalysisContext::flowConditionIsTautology(Atom Token) {
	// Returns true if and only if we cannot prove that the flow condition can
	// ever be false.
	llvm::SetVector<const Formula *> Constraints;
	Constraints.insert(&arena().makeNot(arena().makeAtomRef(Token)));
	llvm::DenseSet<Atom> VisitedTokens;
	addTransitiveFlowConditionConstraints(Token, Constraints, VisitedTokens);
	return isUnsatisfiable(std::move(Constraints));
	}

	bool DataflowAnalysisContext::equivalentFormulas(const Formula &Val1,
	const Formula &Val2) {
	llvm::SetVector<const Formula *> Constraints;
	Constraints.insert(&arena().makeNot(arena().makeEquals(Val1, Val2)));
	return isUnsatisfiable(std::move(Constraints));
	}

	void DataflowAnalysisContext::addTransitiveFlowConditionConstraints(
	Atom Token, llvm::SetVector<const Formula *> &Constraints,
	llvm::DenseSet<Atom> &VisitedTokens) {
	auto Res = VisitedTokens.insert(Token);
	if (!Res.second)
	return;

	auto ConstraintsIt = FlowConditionConstraints.find(Token);
	if (ConstraintsIt == FlowConditionConstraints.end()) {
	Constraints.insert(&arena().makeAtomRef(Token));
	} else {
	// Bind flow condition token via `iff` to its set of constraints:
	// FC <=> (C1 ^ C2 ^ ...), where Ci are constraints
	Constraints.insert(&arena().makeEquals(arena().makeAtomRef(Token),
	*ConstraintsIt->second));
	}

	auto DepsIt = FlowConditionDeps.find(Token);
	if (DepsIt != FlowConditionDeps.end()) {
	for (Atom DepToken : DepsIt->second) {
	addTransitiveFlowConditionConstraints(DepToken, Constraints,
	VisitedTokens);
	}
	}
	}

	void DataflowAnalysisContext::dumpFlowCondition(Atom Token,
	llvm::raw_ostream &OS) {
	llvm::SetVector<const Formula *> Constraints;
	Constraints.insert(&arena().makeAtomRef(Token));
	llvm::DenseSet<Atom> VisitedTokens;
	addTransitiveFlowConditionConstraints(Token, Constraints, VisitedTokens);

	// TODO: have formulas know about true/false directly instead
	Atom True = arena().makeLiteral(true).getAtom();
	Atom False = arena().makeLiteral(false).getAtom();
	Formula::AtomNames Names = {{False, "false"}, {True, "true"}};

	for (const auto *Constraint : Constraints) {
	Constraint->print(OS, &Names);
	OS << "\n";
	}
	}

	const ControlFlowContext *
	DataflowAnalysisContext::getControlFlowContext(const FunctionDecl *F) {
	// Canonicalize the key:
	F = F->getDefinition();
	if (F == nullptr)
	return nullptr;
	auto It = FunctionContexts.find(F);
	if (It != FunctionContexts.end())
	return &It->second;

	if (F->hasBody()) {
	auto CFCtx = ControlFlowContext::build(*F);
	// FIXME: Handle errors.
	assert(CFCtx);
	auto Result = FunctionContexts.insert({F, std::move(*CFCtx)});
	return &Result.first->second;
	}

	return nullptr;
	}

	static std::unique_ptr<Logger> makeLoggerFromCommandLine() {
	if (DataflowLog.empty())
	return Logger::textual(llvm::errs());

	llvm::StringRef Dir = DataflowLog;
	if (auto EC = llvm::sys::fs::create_directories(Dir))
	llvm::errs() << "Failed to create log dir: " << EC.message() << "\n";
	// All analysis runs within a process will log to the same directory.
	// Share a counter so they don't all overwrite each other's 0.html.
	// (Don't share a logger, it's not threadsafe).
	static std::atomic<unsigned> Counter = {0};
	auto StreamFactory =
	[Dir(Dir.str())]() mutable -> std::unique_ptr<llvm::raw_ostream> {
	llvm::SmallString<256> File(Dir);
	llvm::sys::path::append(File,
	std::to_string(Counter.fetch_add(1)) + ".html");
	std::error_code EC;
	auto OS = std::make_unique<llvm::raw_fd_ostream>(File, EC);
	if (EC) {
	llvm::errs() << "Failed to create log " << File << ": " << EC.message()
	<< "\n";
	return std::make_unique<llvm::raw_null_ostream>();
	}
	return OS;
	};
	return Logger::html(std::move(StreamFactory));
	}

	DataflowAnalysisContext::DataflowAnalysisContext(std::unique_ptr<Solver> S,
	Options Opts)
	: S(std::move(S)), A(std::make_unique<Arena>()), Opts(Opts) {
	assert(this->S != nullptr);
	// If the -dataflow-log command-line flag was set, synthesize a logger.
	// This is ugly but provides a uniform method for ad-hoc debugging dataflow-
	// based tools.
	if (Opts.Log == nullptr) {
	if (DataflowLog.getNumOccurrences() > 0) {
	LogOwner = makeLoggerFromCommandLine();
	this->Opts.Log = LogOwner.get();
	// FIXME: if the flag is given a value, write an HTML log to a file.
	} else {
	this->Opts.Log = &Logger::null();
	}
	}
	}

	DataflowAnalysisContext::~DataflowAnalysisContext() = default;

	} // namespace dataflow
	} // namespace clang

	using namespace clang;

	const Expr &clang::dataflow::ignoreCFGOmittedNodes(const Expr &E) {
	const Expr *Current = &E;
	if (auto *EWC = dyn_cast<ExprWithCleanups>(Current)) {
	Current = EWC->getSubExpr();
	assert(Current != nullptr);
	}
	Current = Current->IgnoreParens();
	assert(Current != nullptr);
	return *Current;
	}

	const Stmt &clang::dataflow::ignoreCFGOmittedNodes(const Stmt &S) {
	if (auto *E = dyn_cast<Expr>(&S))
	return ignoreCFGOmittedNodes(*E);
	return S;
	}

	// FIXME: Does not precisely handle non-virtual diamond inheritance. A single
	// field decl will be modeled for all instances of the inherited field.
	static void getFieldsFromClassHierarchy(QualType Type,
	clang::dataflow::FieldSet &Fields) {
	if (Type->isIncompleteType() \|\| Type->isDependentType() \|\|
	!Type->isRecordType())
	return;

	for (const FieldDecl *Field : Type->getAsRecordDecl()->fields())
	Fields.insert(Field);
	if (auto *CXXRecord = Type->getAsCXXRecordDecl())
	for (const CXXBaseSpecifier &Base : CXXRecord->bases())
	getFieldsFromClassHierarchy(Base.getType(), Fields);
	}

	/// Gets the set of all fields in the type.
	clang::dataflow::FieldSet clang::dataflow::getObjectFields(QualType Type) {
	FieldSet Fields;
	getFieldsFromClassHierarchy(Type, Fields);
	return Fields;
	}