| //===-- UncheckedOptionalAccessModel.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 dataflow analysis that detects unsafe uses of optional |
| // values. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "clang/Analysis/FlowSensitive/Models/UncheckedOptionalAccessModel.h" |
| #include "clang/AST/ASTContext.h" |
| #include "clang/AST/DeclCXX.h" |
| #include "clang/AST/Expr.h" |
| #include "clang/AST/ExprCXX.h" |
| #include "clang/AST/Stmt.h" |
| #include "clang/ASTMatchers/ASTMatchers.h" |
| #include "clang/ASTMatchers/ASTMatchersMacros.h" |
| #include "clang/Analysis/CFG.h" |
| #include "clang/Analysis/FlowSensitive/CFGMatchSwitch.h" |
| #include "clang/Analysis/FlowSensitive/DataflowEnvironment.h" |
| #include "clang/Analysis/FlowSensitive/Formula.h" |
| #include "clang/Analysis/FlowSensitive/NoopLattice.h" |
| #include "clang/Analysis/FlowSensitive/StorageLocation.h" |
| #include "clang/Analysis/FlowSensitive/Value.h" |
| #include "clang/Basic/SourceLocation.h" |
| #include "llvm/ADT/StringRef.h" |
| #include "llvm/Support/Casting.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include <cassert> |
| #include <memory> |
| #include <optional> |
| #include <utility> |
| #include <vector> |
| |
| namespace clang { |
| namespace dataflow { |
| |
| static bool isTopLevelNamespaceWithName(const NamespaceDecl &NS, |
| llvm::StringRef Name) { |
| return NS.getDeclName().isIdentifier() && NS.getName() == Name && |
| NS.getParent() != nullptr && NS.getParent()->isTranslationUnit(); |
| } |
| |
| static bool hasOptionalClassName(const CXXRecordDecl &RD) { |
| if (!RD.getDeclName().isIdentifier()) |
| return false; |
| |
| if (RD.getName() == "optional") { |
| if (const auto *N = dyn_cast_or_null<NamespaceDecl>(RD.getDeclContext())) |
| return N->isStdNamespace() || isTopLevelNamespaceWithName(*N, "absl"); |
| return false; |
| } |
| |
| if (RD.getName() == "Optional") { |
| // Check whether namespace is "::base" or "::folly". |
| const auto *N = dyn_cast_or_null<NamespaceDecl>(RD.getDeclContext()); |
| return N != nullptr && (isTopLevelNamespaceWithName(*N, "base") || |
| isTopLevelNamespaceWithName(*N, "folly")); |
| } |
| |
| return false; |
| } |
| |
| namespace { |
| |
| using namespace ::clang::ast_matchers; |
| using LatticeTransferState = TransferState<NoopLattice>; |
| |
| AST_MATCHER(CXXRecordDecl, hasOptionalClassNameMatcher) { |
| return hasOptionalClassName(Node); |
| } |
| |
| DeclarationMatcher optionalClass() { |
| return classTemplateSpecializationDecl( |
| hasOptionalClassNameMatcher(), |
| hasTemplateArgument(0, refersToType(type().bind("T")))); |
| } |
| |
| auto optionalOrAliasType() { |
| return hasUnqualifiedDesugaredType( |
| recordType(hasDeclaration(optionalClass()))); |
| } |
| |
| /// Matches any of the spellings of the optional types and sugar, aliases, etc. |
| auto hasOptionalType() { return hasType(optionalOrAliasType()); } |
| |
| auto isOptionalMemberCallWithNameMatcher( |
| ast_matchers::internal::Matcher<NamedDecl> matcher, |
| const std::optional<StatementMatcher> &Ignorable = std::nullopt) { |
| auto Exception = unless(Ignorable ? expr(anyOf(*Ignorable, cxxThisExpr())) |
| : cxxThisExpr()); |
| return cxxMemberCallExpr( |
| on(expr(Exception, |
| anyOf(hasOptionalType(), |
| hasType(pointerType(pointee(optionalOrAliasType())))))), |
| callee(cxxMethodDecl(matcher))); |
| } |
| |
| auto isOptionalOperatorCallWithName( |
| llvm::StringRef operator_name, |
| const std::optional<StatementMatcher> &Ignorable = std::nullopt) { |
| return cxxOperatorCallExpr( |
| hasOverloadedOperatorName(operator_name), |
| callee(cxxMethodDecl(ofClass(optionalClass()))), |
| Ignorable ? callExpr(unless(hasArgument(0, *Ignorable))) : callExpr()); |
| } |
| |
| auto isMakeOptionalCall() { |
| return callExpr(callee(functionDecl(hasAnyName( |
| "std::make_optional", "base::make_optional", |
| "absl::make_optional", "folly::make_optional"))), |
| hasOptionalType()); |
| } |
| |
| auto nulloptTypeDecl() { |
| return namedDecl(hasAnyName("std::nullopt_t", "absl::nullopt_t", |
| "base::nullopt_t", "folly::None")); |
| } |
| |
| auto hasNulloptType() { return hasType(nulloptTypeDecl()); } |
| |
| // `optional` or `nullopt_t` |
| auto hasAnyOptionalType() { |
| return hasType(hasUnqualifiedDesugaredType( |
| recordType(hasDeclaration(anyOf(nulloptTypeDecl(), optionalClass()))))); |
| } |
| |
| auto inPlaceClass() { |
| return recordDecl(hasAnyName("std::in_place_t", "absl::in_place_t", |
| "base::in_place_t", "folly::in_place_t")); |
| } |
| |
| auto isOptionalNulloptConstructor() { |
| return cxxConstructExpr( |
| hasOptionalType(), |
| hasDeclaration(cxxConstructorDecl(parameterCountIs(1), |
| hasParameter(0, hasNulloptType())))); |
| } |
| |
| auto isOptionalInPlaceConstructor() { |
| return cxxConstructExpr(hasOptionalType(), |
| hasArgument(0, hasType(inPlaceClass()))); |
| } |
| |
| auto isOptionalValueOrConversionConstructor() { |
| return cxxConstructExpr( |
| hasOptionalType(), |
| unless(hasDeclaration( |
| cxxConstructorDecl(anyOf(isCopyConstructor(), isMoveConstructor())))), |
| argumentCountIs(1), hasArgument(0, unless(hasNulloptType()))); |
| } |
| |
| auto isOptionalValueOrConversionAssignment() { |
| return cxxOperatorCallExpr( |
| hasOverloadedOperatorName("="), |
| callee(cxxMethodDecl(ofClass(optionalClass()))), |
| unless(hasDeclaration(cxxMethodDecl( |
| anyOf(isCopyAssignmentOperator(), isMoveAssignmentOperator())))), |
| argumentCountIs(2), hasArgument(1, unless(hasNulloptType()))); |
| } |
| |
| auto isNulloptConstructor() { |
| return cxxConstructExpr(hasNulloptType(), argumentCountIs(1), |
| hasArgument(0, hasNulloptType())); |
| } |
| |
| auto isOptionalNulloptAssignment() { |
| return cxxOperatorCallExpr(hasOverloadedOperatorName("="), |
| callee(cxxMethodDecl(ofClass(optionalClass()))), |
| argumentCountIs(2), |
| hasArgument(1, hasNulloptType())); |
| } |
| |
| auto isStdSwapCall() { |
| return callExpr(callee(functionDecl(hasName("std::swap"))), |
| argumentCountIs(2), hasArgument(0, hasOptionalType()), |
| hasArgument(1, hasOptionalType())); |
| } |
| |
| auto isStdForwardCall() { |
| return callExpr(callee(functionDecl(hasName("std::forward"))), |
| argumentCountIs(1), hasArgument(0, hasOptionalType())); |
| } |
| |
| constexpr llvm::StringLiteral ValueOrCallID = "ValueOrCall"; |
| |
| auto isValueOrStringEmptyCall() { |
| // `opt.value_or("").empty()` |
| return cxxMemberCallExpr( |
| callee(cxxMethodDecl(hasName("empty"))), |
| onImplicitObjectArgument(ignoringImplicit( |
| cxxMemberCallExpr(on(expr(unless(cxxThisExpr()))), |
| callee(cxxMethodDecl(hasName("value_or"), |
| ofClass(optionalClass()))), |
| hasArgument(0, stringLiteral(hasSize(0)))) |
| .bind(ValueOrCallID)))); |
| } |
| |
| auto isValueOrNotEqX() { |
| auto ComparesToSame = [](ast_matchers::internal::Matcher<Stmt> Arg) { |
| return hasOperands( |
| ignoringImplicit( |
| cxxMemberCallExpr(on(expr(unless(cxxThisExpr()))), |
| callee(cxxMethodDecl(hasName("value_or"), |
| ofClass(optionalClass()))), |
| hasArgument(0, Arg)) |
| .bind(ValueOrCallID)), |
| ignoringImplicit(Arg)); |
| }; |
| |
| // `opt.value_or(X) != X`, for X is `nullptr`, `""`, or `0`. Ideally, we'd |
| // support this pattern for any expression, but the AST does not have a |
| // generic expression comparison facility, so we specialize to common cases |
| // seen in practice. FIXME: define a matcher that compares values across |
| // nodes, which would let us generalize this to any `X`. |
| return binaryOperation(hasOperatorName("!="), |
| anyOf(ComparesToSame(cxxNullPtrLiteralExpr()), |
| ComparesToSame(stringLiteral(hasSize(0))), |
| ComparesToSame(integerLiteral(equals(0))))); |
| } |
| |
| auto isCallReturningOptional() { |
| return callExpr(hasType(qualType(anyOf( |
| optionalOrAliasType(), referenceType(pointee(optionalOrAliasType())))))); |
| } |
| |
| template <typename L, typename R> |
| auto isComparisonOperatorCall(L lhs_arg_matcher, R rhs_arg_matcher) { |
| return cxxOperatorCallExpr( |
| anyOf(hasOverloadedOperatorName("=="), hasOverloadedOperatorName("!=")), |
| argumentCountIs(2), hasArgument(0, lhs_arg_matcher), |
| hasArgument(1, rhs_arg_matcher)); |
| } |
| |
| /// Ensures that `Expr` is mapped to a `BoolValue` and returns its formula. |
| const Formula &forceBoolValue(Environment &Env, const Expr &Expr) { |
| auto *Value = cast_or_null<BoolValue>(Env.getValue(Expr, SkipPast::None)); |
| if (Value != nullptr) |
| return Value->formula(); |
| |
| auto &Loc = Env.createStorageLocation(Expr); |
| Value = &Env.makeAtomicBoolValue(); |
| Env.setValue(Loc, *Value); |
| Env.setStorageLocation(Expr, Loc); |
| return Value->formula(); |
| } |
| |
| /// Sets `HasValueVal` as the symbolic value that represents the "has_value" |
| /// property of the optional value `OptionalVal`. |
| void setHasValue(Value &OptionalVal, BoolValue &HasValueVal) { |
| OptionalVal.setProperty("has_value", HasValueVal); |
| } |
| |
| /// Creates a symbolic value for an `optional` value at an existing storage |
| /// location. Uses `HasValueVal` as the symbolic value of the "has_value" |
| /// property. |
| StructValue &createOptionalValue(AggregateStorageLocation &Loc, |
| BoolValue &HasValueVal, Environment &Env) { |
| auto &OptionalVal = Env.create<StructValue>(Loc); |
| Env.setValue(Loc, OptionalVal); |
| setHasValue(OptionalVal, HasValueVal); |
| return OptionalVal; |
| } |
| |
| /// Returns the symbolic value that represents the "has_value" property of the |
| /// optional value `OptionalVal`. Returns null if `OptionalVal` is null. |
| BoolValue *getHasValue(Environment &Env, Value *OptionalVal) { |
| if (OptionalVal != nullptr) { |
| auto *HasValueVal = |
| cast_or_null<BoolValue>(OptionalVal->getProperty("has_value")); |
| if (HasValueVal == nullptr) { |
| HasValueVal = &Env.makeAtomicBoolValue(); |
| OptionalVal->setProperty("has_value", *HasValueVal); |
| } |
| return HasValueVal; |
| } |
| return nullptr; |
| } |
| |
| /// Returns true if and only if `Type` is an optional type. |
| bool isOptionalType(QualType Type) { |
| if (!Type->isRecordType()) |
| return false; |
| const CXXRecordDecl *D = Type->getAsCXXRecordDecl(); |
| return D != nullptr && hasOptionalClassName(*D); |
| } |
| |
| /// Returns the number of optional wrappers in `Type`. |
| /// |
| /// For example, if `Type` is `optional<optional<int>>`, the result of this |
| /// function will be 2. |
| int countOptionalWrappers(const ASTContext &ASTCtx, QualType Type) { |
| if (!isOptionalType(Type)) |
| return 0; |
| return 1 + countOptionalWrappers( |
| ASTCtx, |
| cast<ClassTemplateSpecializationDecl>(Type->getAsRecordDecl()) |
| ->getTemplateArgs() |
| .get(0) |
| .getAsType() |
| .getDesugaredType(ASTCtx)); |
| } |
| |
| /// Tries to initialize the `optional`'s value (that is, contents), and return |
| /// its location. Returns nullptr if the value can't be represented. |
| StorageLocation *maybeInitializeOptionalValueMember(QualType Q, |
| Value &OptionalVal, |
| Environment &Env) { |
| // The "value" property represents a synthetic field. As such, it needs |
| // `StorageLocation`, like normal fields (and other variables). So, we model |
| // it with a `PointerValue`, since that includes a storage location. Once |
| // the property is set, it will be shared by all environments that access the |
| // `Value` representing the optional (here, `OptionalVal`). |
| if (auto *ValueProp = OptionalVal.getProperty("value")) { |
| auto *ValuePtr = clang::cast<PointerValue>(ValueProp); |
| auto &ValueLoc = ValuePtr->getPointeeLoc(); |
| if (Env.getValue(ValueLoc) != nullptr) |
| return &ValueLoc; |
| |
| // The property was previously set, but the value has been lost. This can |
| // happen in various situations, for example: |
| // - Because of an environment merge (where the two environments mapped the |
| // property to different values, which resulted in them both being |
| // discarded). |
| // - When two blocks in the CFG, with neither a dominator of the other, |
| // visit the same optional value. (FIXME: This is something we can and |
| // should fix -- see also the lengthy FIXME below.) |
| // - Or even when a block is revisited during testing to collect |
| // per-statement state. |
| // FIXME: This situation means that the optional contents are not shared |
| // between branches and the like. Practically, this lack of sharing |
| // reduces the precision of the model when the contents are relevant to |
| // the check, like another optional or a boolean that influences control |
| // flow. |
| if (ValueLoc.getType()->isRecordType()) { |
| refreshStructValue(cast<AggregateStorageLocation>(ValueLoc), Env); |
| return &ValueLoc; |
| } else { |
| auto *ValueVal = Env.createValue(ValueLoc.getType()); |
| if (ValueVal == nullptr) |
| return nullptr; |
| Env.setValue(ValueLoc, *ValueVal); |
| return &ValueLoc; |
| } |
| } |
| |
| auto Ty = Q.getNonReferenceType(); |
| auto &ValueLoc = Env.createObject(Ty); |
| auto &ValuePtr = Env.create<PointerValue>(ValueLoc); |
| // FIXME: |
| // The change we make to the `value` property below may become visible to |
| // other blocks that aren't successors of the current block and therefore |
| // don't see the change we made above mapping `ValueLoc` to `ValueVal`. For |
| // example: |
| // |
| // void target(optional<int> oo, bool b) { |
| // // `oo` is associated with a `StructValue` here, which we will call |
| // // `OptionalVal`. |
| // |
| // // The `has_value` property is set on `OptionalVal` (but not the |
| // // `value` property yet). |
| // if (!oo.has_value()) return; |
| // |
| // if (b) { |
| // // Let's assume we transfer the `if` branch first. |
| // // |
| // // This causes us to call `maybeInitializeOptionalValueMember()`, |
| // // which causes us to set the `value` property on `OptionalVal` |
| // // (which had not been set until this point). This `value` property |
| // // refers to a `PointerValue`, which in turn refers to a |
| // // StorageLocation` that is associated to an `IntegerValue`. |
| // oo.value(); |
| // } else { |
| // // Let's assume we transfer the `else` branch after the `if` branch. |
| // // |
| // // We see the `value` property that the `if` branch set on |
| // // `OptionalVal`, but in the environment for this block, the |
| // // `StorageLocation` in the `PointerValue` is not associated with any |
| // // `Value`. |
| // oo.value(); |
| // } |
| // } |
| // |
| // This situation is currently "saved" by the code above that checks whether |
| // the `value` property is already set, and if, the `ValueLoc` is not |
| // associated with a `ValueVal`, creates a new `ValueVal`. |
| // |
| // However, what we should really do is to make sure that the change to the |
| // `value` property does not "leak" to other blocks that are not successors |
| // of this block. To do this, instead of simply setting the `value` property |
| // on the existing `OptionalVal`, we should create a new `Value` for the |
| // optional, set the property on that, and associate the storage location that |
| // is currently associated with the existing `OptionalVal` with the newly |
| // created `Value` instead. |
| OptionalVal.setProperty("value", ValuePtr); |
| return &ValueLoc; |
| } |
| |
| void initializeOptionalReference(const Expr *OptionalExpr, |
| const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| if (auto *OptionalVal = |
| State.Env.getValue(*OptionalExpr, SkipPast::Reference)) { |
| if (OptionalVal->getProperty("has_value") == nullptr) { |
| setHasValue(*OptionalVal, State.Env.makeAtomicBoolValue()); |
| } |
| } |
| } |
| |
| /// Returns true if and only if `OptionalVal` is initialized and known to be |
| /// empty in `Env`. |
| bool isEmptyOptional(const Value &OptionalVal, const Environment &Env) { |
| auto *HasValueVal = |
| cast_or_null<BoolValue>(OptionalVal.getProperty("has_value")); |
| return HasValueVal != nullptr && |
| Env.flowConditionImplies(Env.arena().makeNot(HasValueVal->formula())); |
| } |
| |
| /// Returns true if and only if `OptionalVal` is initialized and known to be |
| /// non-empty in `Env`. |
| bool isNonEmptyOptional(const Value &OptionalVal, const Environment &Env) { |
| auto *HasValueVal = |
| cast_or_null<BoolValue>(OptionalVal.getProperty("has_value")); |
| return HasValueVal != nullptr && |
| Env.flowConditionImplies(HasValueVal->formula()); |
| } |
| |
| Value *getValueBehindPossiblePointer(const Expr &E, const Environment &Env) { |
| Value *Val = Env.getValue(E, SkipPast::Reference); |
| if (auto *PointerVal = dyn_cast_or_null<PointerValue>(Val)) |
| return Env.getValue(PointerVal->getPointeeLoc()); |
| return Val; |
| } |
| |
| void transferUnwrapCall(const Expr *UnwrapExpr, const Expr *ObjectExpr, |
| LatticeTransferState &State) { |
| if (auto *OptionalVal = |
| getValueBehindPossiblePointer(*ObjectExpr, State.Env)) { |
| if (State.Env.getStorageLocation(*UnwrapExpr, SkipPast::None) == nullptr) |
| if (auto *Loc = maybeInitializeOptionalValueMember( |
| UnwrapExpr->getType(), *OptionalVal, State.Env)) |
| State.Env.setStorageLocation(*UnwrapExpr, *Loc); |
| } |
| } |
| |
| void transferArrowOpCall(const Expr *UnwrapExpr, const Expr *ObjectExpr, |
| LatticeTransferState &State) { |
| if (auto *OptionalVal = |
| getValueBehindPossiblePointer(*ObjectExpr, State.Env)) { |
| if (auto *Loc = maybeInitializeOptionalValueMember( |
| UnwrapExpr->getType()->getPointeeType(), *OptionalVal, State.Env)) { |
| State.Env.setValueStrict(*UnwrapExpr, |
| State.Env.create<PointerValue>(*Loc)); |
| } |
| } |
| } |
| |
| void transferMakeOptionalCall(const CallExpr *E, |
| const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| createOptionalValue(State.Env.getResultObjectLocation(*E), |
| State.Env.getBoolLiteralValue(true), State.Env); |
| } |
| |
| void transferOptionalHasValueCall(const CXXMemberCallExpr *CallExpr, |
| const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| if (auto *HasValueVal = getHasValue( |
| State.Env, getValueBehindPossiblePointer( |
| *CallExpr->getImplicitObjectArgument(), State.Env))) { |
| auto &CallExprLoc = State.Env.createStorageLocation(*CallExpr); |
| State.Env.setValue(CallExprLoc, *HasValueVal); |
| State.Env.setStorageLocation(*CallExpr, CallExprLoc); |
| } |
| } |
| |
| /// `ModelPred` builds a logical formula relating the predicate in |
| /// `ValueOrPredExpr` to the optional's `has_value` property. |
| void transferValueOrImpl( |
| const clang::Expr *ValueOrPredExpr, const MatchFinder::MatchResult &Result, |
| LatticeTransferState &State, |
| const Formula &(*ModelPred)(Environment &Env, const Formula &ExprVal, |
| const Formula &HasValueVal)) { |
| auto &Env = State.Env; |
| |
| const auto *ObjectArgumentExpr = |
| Result.Nodes.getNodeAs<clang::CXXMemberCallExpr>(ValueOrCallID) |
| ->getImplicitObjectArgument(); |
| |
| auto *HasValueVal = getHasValue( |
| State.Env, getValueBehindPossiblePointer(*ObjectArgumentExpr, State.Env)); |
| if (HasValueVal == nullptr) |
| return; |
| |
| Env.addToFlowCondition(ModelPred(Env, forceBoolValue(Env, *ValueOrPredExpr), |
| HasValueVal->formula())); |
| } |
| |
| void transferValueOrStringEmptyCall(const clang::Expr *ComparisonExpr, |
| const MatchFinder::MatchResult &Result, |
| LatticeTransferState &State) { |
| return transferValueOrImpl(ComparisonExpr, Result, State, |
| [](Environment &Env, const Formula &ExprVal, |
| const Formula &HasValueVal) -> const Formula & { |
| auto &A = Env.arena(); |
| // If the result is *not* empty, then we know the |
| // optional must have been holding a value. If |
| // `ExprVal` is true, though, we don't learn |
| // anything definite about `has_value`, so we |
| // don't add any corresponding implications to |
| // the flow condition. |
| return A.makeImplies(A.makeNot(ExprVal), |
| HasValueVal); |
| }); |
| } |
| |
| void transferValueOrNotEqX(const Expr *ComparisonExpr, |
| const MatchFinder::MatchResult &Result, |
| LatticeTransferState &State) { |
| transferValueOrImpl(ComparisonExpr, Result, State, |
| [](Environment &Env, const Formula &ExprVal, |
| const Formula &HasValueVal) -> const Formula & { |
| auto &A = Env.arena(); |
| // We know that if `(opt.value_or(X) != X)` then |
| // `opt.hasValue()`, even without knowing further |
| // details about the contents of `opt`. |
| return A.makeImplies(ExprVal, HasValueVal); |
| }); |
| } |
| |
| void transferCallReturningOptional(const CallExpr *E, |
| const MatchFinder::MatchResult &Result, |
| LatticeTransferState &State) { |
| if (State.Env.getStorageLocation(*E, SkipPast::None) != nullptr) |
| return; |
| |
| AggregateStorageLocation *Loc = nullptr; |
| if (E->isPRValue()) { |
| Loc = &State.Env.getResultObjectLocation(*E); |
| } else { |
| Loc = &cast<AggregateStorageLocation>(State.Env.createStorageLocation(*E)); |
| State.Env.setStorageLocationStrict(*E, *Loc); |
| } |
| |
| createOptionalValue(*Loc, State.Env.makeAtomicBoolValue(), State.Env); |
| } |
| |
| void constructOptionalValue(const Expr &E, Environment &Env, |
| BoolValue &HasValueVal) { |
| AggregateStorageLocation &Loc = Env.getResultObjectLocation(E); |
| Env.setValueStrict(E, createOptionalValue(Loc, HasValueVal, Env)); |
| } |
| |
| /// Returns a symbolic value for the "has_value" property of an `optional<T>` |
| /// value that is constructed/assigned from a value of type `U` or `optional<U>` |
| /// where `T` is constructible from `U`. |
| BoolValue &valueOrConversionHasValue(const FunctionDecl &F, const Expr &E, |
| const MatchFinder::MatchResult &MatchRes, |
| LatticeTransferState &State) { |
| assert(F.getTemplateSpecializationArgs() != nullptr); |
| assert(F.getTemplateSpecializationArgs()->size() > 0); |
| |
| const int TemplateParamOptionalWrappersCount = |
| countOptionalWrappers(*MatchRes.Context, F.getTemplateSpecializationArgs() |
| ->get(0) |
| .getAsType() |
| .getNonReferenceType()); |
| const int ArgTypeOptionalWrappersCount = countOptionalWrappers( |
| *MatchRes.Context, E.getType().getNonReferenceType()); |
| |
| // Check if this is a constructor/assignment call for `optional<T>` with |
| // argument of type `U` such that `T` is constructible from `U`. |
| if (TemplateParamOptionalWrappersCount == ArgTypeOptionalWrappersCount) |
| return State.Env.getBoolLiteralValue(true); |
| |
| // This is a constructor/assignment call for `optional<T>` with argument of |
| // type `optional<U>` such that `T` is constructible from `U`. |
| if (auto *HasValueVal = |
| getHasValue(State.Env, State.Env.getValue(E, SkipPast::Reference))) |
| return *HasValueVal; |
| return State.Env.makeAtomicBoolValue(); |
| } |
| |
| void transferValueOrConversionConstructor( |
| const CXXConstructExpr *E, const MatchFinder::MatchResult &MatchRes, |
| LatticeTransferState &State) { |
| assert(E->getNumArgs() > 0); |
| |
| constructOptionalValue(*E, State.Env, |
| valueOrConversionHasValue(*E->getConstructor(), |
| *E->getArg(0), MatchRes, |
| State)); |
| } |
| |
| void transferAssignment(const CXXOperatorCallExpr *E, BoolValue &HasValueVal, |
| LatticeTransferState &State) { |
| assert(E->getNumArgs() > 0); |
| |
| if (auto *Loc = cast<AggregateStorageLocation>( |
| State.Env.getStorageLocationStrict(*E->getArg(0)))) { |
| createOptionalValue(*Loc, HasValueVal, State.Env); |
| |
| // Assign a storage location for the whole expression. |
| State.Env.setStorageLocationStrict(*E, *Loc); |
| } |
| } |
| |
| void transferValueOrConversionAssignment( |
| const CXXOperatorCallExpr *E, const MatchFinder::MatchResult &MatchRes, |
| LatticeTransferState &State) { |
| assert(E->getNumArgs() > 1); |
| transferAssignment(E, |
| valueOrConversionHasValue(*E->getDirectCallee(), |
| *E->getArg(1), MatchRes, State), |
| State); |
| } |
| |
| void transferNulloptAssignment(const CXXOperatorCallExpr *E, |
| const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| transferAssignment(E, State.Env.getBoolLiteralValue(false), State); |
| } |
| |
| void transferSwap(AggregateStorageLocation *Loc1, |
| AggregateStorageLocation *Loc2, Environment &Env) { |
| // We account for cases where one or both of the optionals are not modeled, |
| // either lacking associated storage locations, or lacking values associated |
| // to such storage locations. |
| |
| if (Loc1 == nullptr) { |
| if (Loc2 != nullptr) |
| createOptionalValue(*Loc2, Env.makeAtomicBoolValue(), Env); |
| return; |
| } |
| if (Loc2 == nullptr) { |
| createOptionalValue(*Loc1, Env.makeAtomicBoolValue(), Env); |
| return; |
| } |
| |
| // Both expressions have locations, though they may not have corresponding |
| // values. In that case, we create a fresh value at this point. Note that if |
| // two branches both do this, they will not share the value, but it at least |
| // allows for local reasoning about the value. To avoid the above, we would |
| // need *lazy* value allocation. |
| // FIXME: allocate values lazily, instead of just creating a fresh value. |
| BoolValue *BoolVal1 = getHasValue(Env, Env.getValue(*Loc1)); |
| if (BoolVal1 == nullptr) |
| BoolVal1 = &Env.makeAtomicBoolValue(); |
| |
| BoolValue *BoolVal2 = getHasValue(Env, Env.getValue(*Loc2)); |
| if (BoolVal2 == nullptr) |
| BoolVal2 = &Env.makeAtomicBoolValue(); |
| |
| createOptionalValue(*Loc1, *BoolVal2, Env); |
| createOptionalValue(*Loc2, *BoolVal1, Env); |
| } |
| |
| void transferSwapCall(const CXXMemberCallExpr *E, |
| const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| assert(E->getNumArgs() == 1); |
| auto *OtherLoc = cast_or_null<AggregateStorageLocation>( |
| State.Env.getStorageLocationStrict(*E->getArg(0))); |
| transferSwap(getImplicitObjectLocation(*E, State.Env), OtherLoc, State.Env); |
| } |
| |
| void transferStdSwapCall(const CallExpr *E, const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| assert(E->getNumArgs() == 2); |
| auto *Arg0Loc = cast_or_null<AggregateStorageLocation>( |
| State.Env.getStorageLocationStrict(*E->getArg(0))); |
| auto *Arg1Loc = cast_or_null<AggregateStorageLocation>( |
| State.Env.getStorageLocationStrict(*E->getArg(1))); |
| transferSwap(Arg0Loc, Arg1Loc, State.Env); |
| } |
| |
| void transferStdForwardCall(const CallExpr *E, const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| assert(E->getNumArgs() == 1); |
| |
| if (auto *Loc = State.Env.getStorageLocationStrict(*E->getArg(0))) |
| State.Env.setStorageLocationStrict(*E, *Loc); |
| } |
| |
| const Formula &evaluateEquality(Arena &A, const Formula &EqVal, |
| const Formula &LHS, const Formula &RHS) { |
| // Logically, an optional<T> object is composed of two values - a `has_value` |
| // bit and a value of type T. Equality of optional objects compares both |
| // values. Therefore, merely comparing the `has_value` bits isn't sufficient: |
| // when two optional objects are engaged, the equality of their respective |
| // values of type T matters. Since we only track the `has_value` bits, we |
| // can't make any conclusions about equality when we know that two optional |
| // objects are engaged. |
| // |
| // We express this as two facts about the equality: |
| // a) EqVal => (LHS & RHS) v (!RHS & !LHS) |
| // If they are equal, then either both are set or both are unset. |
| // b) (!LHS & !RHS) => EqVal |
| // If neither is set, then they are equal. |
| // We rewrite b) as !EqVal => (LHS v RHS), for a more compact formula. |
| return A.makeAnd( |
| A.makeImplies(EqVal, A.makeOr(A.makeAnd(LHS, RHS), |
| A.makeAnd(A.makeNot(LHS), A.makeNot(RHS)))), |
| A.makeImplies(A.makeNot(EqVal), A.makeOr(LHS, RHS))); |
| } |
| |
| void transferOptionalAndOptionalCmp(const clang::CXXOperatorCallExpr *CmpExpr, |
| const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| Environment &Env = State.Env; |
| auto &A = Env.arena(); |
| auto *CmpValue = &forceBoolValue(Env, *CmpExpr); |
| if (auto *LHasVal = getHasValue( |
| Env, Env.getValue(*CmpExpr->getArg(0), SkipPast::Reference))) |
| if (auto *RHasVal = getHasValue( |
| Env, Env.getValue(*CmpExpr->getArg(1), SkipPast::Reference))) { |
| if (CmpExpr->getOperator() == clang::OO_ExclaimEqual) |
| CmpValue = &A.makeNot(*CmpValue); |
| Env.addToFlowCondition(evaluateEquality(A, *CmpValue, LHasVal->formula(), |
| RHasVal->formula())); |
| } |
| } |
| |
| void transferOptionalAndValueCmp(const clang::CXXOperatorCallExpr *CmpExpr, |
| const clang::Expr *E, Environment &Env) { |
| auto &A = Env.arena(); |
| auto *CmpValue = &forceBoolValue(Env, *CmpExpr); |
| if (auto *HasVal = getHasValue(Env, Env.getValue(*E, SkipPast::Reference))) { |
| if (CmpExpr->getOperator() == clang::OO_ExclaimEqual) |
| CmpValue = &A.makeNot(*CmpValue); |
| Env.addToFlowCondition( |
| evaluateEquality(A, *CmpValue, HasVal->formula(), A.makeLiteral(true))); |
| } |
| } |
| |
| std::optional<StatementMatcher> |
| ignorableOptional(const UncheckedOptionalAccessModelOptions &Options) { |
| if (Options.IgnoreSmartPointerDereference) { |
| auto SmartPtrUse = expr(ignoringParenImpCasts(cxxOperatorCallExpr( |
| anyOf(hasOverloadedOperatorName("->"), hasOverloadedOperatorName("*")), |
| unless(hasArgument(0, expr(hasOptionalType())))))); |
| return expr( |
| anyOf(SmartPtrUse, memberExpr(hasObjectExpression(SmartPtrUse)))); |
| } |
| return std::nullopt; |
| } |
| |
| StatementMatcher |
| valueCall(const std::optional<StatementMatcher> &IgnorableOptional) { |
| return isOptionalMemberCallWithNameMatcher(hasName("value"), |
| IgnorableOptional); |
| } |
| |
| StatementMatcher |
| valueOperatorCall(const std::optional<StatementMatcher> &IgnorableOptional) { |
| return expr(anyOf(isOptionalOperatorCallWithName("*", IgnorableOptional), |
| isOptionalOperatorCallWithName("->", IgnorableOptional))); |
| } |
| |
| auto buildTransferMatchSwitch() { |
| // FIXME: Evaluate the efficiency of matchers. If using matchers results in a |
| // lot of duplicated work (e.g. string comparisons), consider providing APIs |
| // that avoid it through memoization. |
| return CFGMatchSwitchBuilder<LatticeTransferState>() |
| // Attach a symbolic "has_value" state to optional values that we see for |
| // the first time. |
| .CaseOfCFGStmt<Expr>( |
| expr(anyOf(declRefExpr(), memberExpr()), hasOptionalType()), |
| initializeOptionalReference) |
| |
| // make_optional |
| .CaseOfCFGStmt<CallExpr>(isMakeOptionalCall(), transferMakeOptionalCall) |
| |
| // optional::optional (in place) |
| .CaseOfCFGStmt<CXXConstructExpr>( |
| isOptionalInPlaceConstructor(), |
| [](const CXXConstructExpr *E, const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| constructOptionalValue(*E, State.Env, |
| State.Env.getBoolLiteralValue(true)); |
| }) |
| // nullopt_t::nullopt_t |
| .CaseOfCFGStmt<CXXConstructExpr>( |
| isNulloptConstructor(), |
| [](const CXXConstructExpr *E, const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| constructOptionalValue(*E, State.Env, |
| State.Env.getBoolLiteralValue(false)); |
| }) |
| // optional::optional(nullopt_t) |
| .CaseOfCFGStmt<CXXConstructExpr>( |
| isOptionalNulloptConstructor(), |
| [](const CXXConstructExpr *E, const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| constructOptionalValue(*E, State.Env, |
| State.Env.getBoolLiteralValue(false)); |
| }) |
| // optional::optional (value/conversion) |
| .CaseOfCFGStmt<CXXConstructExpr>(isOptionalValueOrConversionConstructor(), |
| transferValueOrConversionConstructor) |
| |
| // optional::operator= |
| .CaseOfCFGStmt<CXXOperatorCallExpr>( |
| isOptionalValueOrConversionAssignment(), |
| transferValueOrConversionAssignment) |
| .CaseOfCFGStmt<CXXOperatorCallExpr>(isOptionalNulloptAssignment(), |
| transferNulloptAssignment) |
| |
| // optional::value |
| .CaseOfCFGStmt<CXXMemberCallExpr>( |
| valueCall(std::nullopt), |
| [](const CXXMemberCallExpr *E, const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| transferUnwrapCall(E, E->getImplicitObjectArgument(), State); |
| }) |
| |
| // optional::operator* |
| .CaseOfCFGStmt<CallExpr>(isOptionalOperatorCallWithName("*"), |
| [](const CallExpr *E, |
| const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| transferUnwrapCall(E, E->getArg(0), State); |
| }) |
| |
| // optional::operator-> |
| .CaseOfCFGStmt<CallExpr>(isOptionalOperatorCallWithName("->"), |
| [](const CallExpr *E, |
| const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| transferArrowOpCall(E, E->getArg(0), State); |
| }) |
| |
| // optional::has_value, optional::hasValue |
| // Of the supported optionals only folly::Optional uses hasValue, but this |
| // will also pass for other types |
| .CaseOfCFGStmt<CXXMemberCallExpr>( |
| isOptionalMemberCallWithNameMatcher( |
| hasAnyName("has_value", "hasValue")), |
| transferOptionalHasValueCall) |
| |
| // optional::operator bool |
| .CaseOfCFGStmt<CXXMemberCallExpr>( |
| isOptionalMemberCallWithNameMatcher(hasName("operator bool")), |
| transferOptionalHasValueCall) |
| |
| // optional::emplace |
| .CaseOfCFGStmt<CXXMemberCallExpr>( |
| isOptionalMemberCallWithNameMatcher(hasName("emplace")), |
| [](const CXXMemberCallExpr *E, const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| if (AggregateStorageLocation *Loc = |
| getImplicitObjectLocation(*E, State.Env)) { |
| createOptionalValue(*Loc, State.Env.getBoolLiteralValue(true), |
| State.Env); |
| } |
| }) |
| |
| // optional::reset |
| .CaseOfCFGStmt<CXXMemberCallExpr>( |
| isOptionalMemberCallWithNameMatcher(hasName("reset")), |
| [](const CXXMemberCallExpr *E, const MatchFinder::MatchResult &, |
| LatticeTransferState &State) { |
| if (AggregateStorageLocation *Loc = |
| getImplicitObjectLocation(*E, State.Env)) { |
| createOptionalValue(*Loc, State.Env.getBoolLiteralValue(false), |
| State.Env); |
| } |
| }) |
| |
| // optional::swap |
| .CaseOfCFGStmt<CXXMemberCallExpr>( |
| isOptionalMemberCallWithNameMatcher(hasName("swap")), |
| transferSwapCall) |
| |
| // std::swap |
| .CaseOfCFGStmt<CallExpr>(isStdSwapCall(), transferStdSwapCall) |
| |
| // std::forward |
| .CaseOfCFGStmt<CallExpr>(isStdForwardCall(), transferStdForwardCall) |
| |
| // opt.value_or("").empty() |
| .CaseOfCFGStmt<Expr>(isValueOrStringEmptyCall(), |
| transferValueOrStringEmptyCall) |
| |
| // opt.value_or(X) != X |
| .CaseOfCFGStmt<Expr>(isValueOrNotEqX(), transferValueOrNotEqX) |
| |
| // Comparisons (==, !=): |
| .CaseOfCFGStmt<CXXOperatorCallExpr>( |
| isComparisonOperatorCall(hasAnyOptionalType(), hasAnyOptionalType()), |
| transferOptionalAndOptionalCmp) |
| .CaseOfCFGStmt<CXXOperatorCallExpr>( |
| isComparisonOperatorCall(hasOptionalType(), |
| unless(hasAnyOptionalType())), |
| [](const clang::CXXOperatorCallExpr *Cmp, |
| const MatchFinder::MatchResult &, LatticeTransferState &State) { |
| transferOptionalAndValueCmp(Cmp, Cmp->getArg(0), State.Env); |
| }) |
| .CaseOfCFGStmt<CXXOperatorCallExpr>( |
| isComparisonOperatorCall(unless(hasAnyOptionalType()), |
| hasOptionalType()), |
| [](const clang::CXXOperatorCallExpr *Cmp, |
| const MatchFinder::MatchResult &, LatticeTransferState &State) { |
| transferOptionalAndValueCmp(Cmp, Cmp->getArg(1), State.Env); |
| }) |
| |
| // returns optional |
| .CaseOfCFGStmt<CallExpr>(isCallReturningOptional(), |
| transferCallReturningOptional) |
| |
| .Build(); |
| } |
| |
| std::vector<SourceLocation> diagnoseUnwrapCall(const Expr *ObjectExpr, |
| const Environment &Env) { |
| if (auto *OptionalVal = getValueBehindPossiblePointer(*ObjectExpr, Env)) { |
| auto *Prop = OptionalVal->getProperty("has_value"); |
| if (auto *HasValueVal = cast_or_null<BoolValue>(Prop)) { |
| if (Env.flowConditionImplies(HasValueVal->formula())) |
| return {}; |
| } |
| } |
| |
| // Record that this unwrap is *not* provably safe. |
| // FIXME: include either the name of the optional (if applicable) or a source |
| // range of the access for easier interpretation of the result. |
| return {ObjectExpr->getBeginLoc()}; |
| } |
| |
| auto buildDiagnoseMatchSwitch( |
| const UncheckedOptionalAccessModelOptions &Options) { |
| // FIXME: Evaluate the efficiency of matchers. If using matchers results in a |
| // lot of duplicated work (e.g. string comparisons), consider providing APIs |
| // that avoid it through memoization. |
| auto IgnorableOptional = ignorableOptional(Options); |
| return CFGMatchSwitchBuilder<const Environment, std::vector<SourceLocation>>() |
| // optional::value |
| .CaseOfCFGStmt<CXXMemberCallExpr>( |
| valueCall(IgnorableOptional), |
| [](const CXXMemberCallExpr *E, const MatchFinder::MatchResult &, |
| const Environment &Env) { |
| return diagnoseUnwrapCall(E->getImplicitObjectArgument(), Env); |
| }) |
| |
| // optional::operator*, optional::operator-> |
| .CaseOfCFGStmt<CallExpr>(valueOperatorCall(IgnorableOptional), |
| [](const CallExpr *E, |
| const MatchFinder::MatchResult &, |
| const Environment &Env) { |
| return diagnoseUnwrapCall(E->getArg(0), Env); |
| }) |
| .Build(); |
| } |
| |
| } // namespace |
| |
| ast_matchers::DeclarationMatcher |
| UncheckedOptionalAccessModel::optionalClassDecl() { |
| return optionalClass(); |
| } |
| |
| UncheckedOptionalAccessModel::UncheckedOptionalAccessModel(ASTContext &Ctx) |
| : DataflowAnalysis<UncheckedOptionalAccessModel, NoopLattice>(Ctx), |
| TransferMatchSwitch(buildTransferMatchSwitch()) {} |
| |
| void UncheckedOptionalAccessModel::transfer(const CFGElement &Elt, |
| NoopLattice &L, Environment &Env) { |
| LatticeTransferState State(L, Env); |
| TransferMatchSwitch(Elt, getASTContext(), State); |
| } |
| |
| ComparisonResult UncheckedOptionalAccessModel::compare( |
| QualType Type, const Value &Val1, const Environment &Env1, |
| const Value &Val2, const Environment &Env2) { |
| if (!isOptionalType(Type)) |
| return ComparisonResult::Unknown; |
| bool MustNonEmpty1 = isNonEmptyOptional(Val1, Env1); |
| bool MustNonEmpty2 = isNonEmptyOptional(Val2, Env2); |
| if (MustNonEmpty1 && MustNonEmpty2) |
| return ComparisonResult::Same; |
| // If exactly one is true, then they're different, no reason to check whether |
| // they're definitely empty. |
| if (MustNonEmpty1 || MustNonEmpty2) |
| return ComparisonResult::Different; |
| // Check if they're both definitely empty. |
| return (isEmptyOptional(Val1, Env1) && isEmptyOptional(Val2, Env2)) |
| ? ComparisonResult::Same |
| : ComparisonResult::Different; |
| } |
| |
| bool UncheckedOptionalAccessModel::merge(QualType Type, const Value &Val1, |
| const Environment &Env1, |
| const Value &Val2, |
| const Environment &Env2, |
| Value &MergedVal, |
| Environment &MergedEnv) { |
| if (!isOptionalType(Type)) |
| return true; |
| // FIXME: uses same approach as join for `BoolValues`. Requires non-const |
| // values, though, so will require updating the interface. |
| auto &HasValueVal = MergedEnv.makeAtomicBoolValue(); |
| bool MustNonEmpty1 = isNonEmptyOptional(Val1, Env1); |
| bool MustNonEmpty2 = isNonEmptyOptional(Val2, Env2); |
| if (MustNonEmpty1 && MustNonEmpty2) |
| MergedEnv.addToFlowCondition(HasValueVal.formula()); |
| else if ( |
| // Only make the costly calls to `isEmptyOptional` if we got "unknown" |
| // (false) for both calls to `isNonEmptyOptional`. |
| !MustNonEmpty1 && !MustNonEmpty2 && isEmptyOptional(Val1, Env1) && |
| isEmptyOptional(Val2, Env2)) |
| MergedEnv.addToFlowCondition( |
| MergedEnv.arena().makeNot(HasValueVal.formula())); |
| setHasValue(MergedVal, HasValueVal); |
| return true; |
| } |
| |
| Value *UncheckedOptionalAccessModel::widen(QualType Type, Value &Prev, |
| const Environment &PrevEnv, |
| Value &Current, |
| Environment &CurrentEnv) { |
| switch (compare(Type, Prev, PrevEnv, Current, CurrentEnv)) { |
| case ComparisonResult::Same: |
| return &Prev; |
| case ComparisonResult::Different: |
| if (auto *PrevHasVal = |
| cast_or_null<BoolValue>(Prev.getProperty("has_value"))) { |
| if (isa<TopBoolValue>(PrevHasVal)) |
| return &Prev; |
| } |
| if (auto *CurrentHasVal = |
| cast_or_null<BoolValue>(Current.getProperty("has_value"))) { |
| if (isa<TopBoolValue>(CurrentHasVal)) |
| return &Current; |
| } |
| return &createOptionalValue(cast<StructValue>(Current).getAggregateLoc(), |
| CurrentEnv.makeTopBoolValue(), CurrentEnv); |
| case ComparisonResult::Unknown: |
| return nullptr; |
| } |
| llvm_unreachable("all cases covered in switch"); |
| } |
| |
| UncheckedOptionalAccessDiagnoser::UncheckedOptionalAccessDiagnoser( |
| UncheckedOptionalAccessModelOptions Options) |
| : DiagnoseMatchSwitch(buildDiagnoseMatchSwitch(Options)) {} |
| |
| std::vector<SourceLocation> UncheckedOptionalAccessDiagnoser::diagnose( |
| ASTContext &Ctx, const CFGElement *Elt, const Environment &Env) { |
| return DiagnoseMatchSwitch(*Elt, Ctx, Env); |
| } |
| |
| } // namespace dataflow |
| } // namespace clang |
