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| //===--- ExceptionAnalyzer.cpp - clang-tidy -------------------------------===//
//
// 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 "ExceptionAnalyzer.h"
namespace clang {
namespace tidy {
namespace utils {
void ExceptionAnalyzer::ExceptionInfo::registerException(
const Type *ExceptionType) {
assert(ExceptionType != nullptr && "Only valid types are accepted");
Behaviour = State::Throwing;
ThrownExceptions.insert(ExceptionType);
}
void ExceptionAnalyzer::ExceptionInfo::registerExceptions(
const Throwables &Exceptions) {
if (Exceptions.size() == 0)
return;
Behaviour = State::Throwing;
ThrownExceptions.insert(Exceptions.begin(), Exceptions.end());
}
ExceptionAnalyzer::ExceptionInfo &ExceptionAnalyzer::ExceptionInfo::merge(
const ExceptionAnalyzer::ExceptionInfo &Other) {
// Only the following two cases require an update to the local
// 'Behaviour'. If the local entity is already throwing there will be no
// change and if the other entity is throwing the merged entity will throw
// as well.
// If one of both entities is 'Unknown' and the other one does not throw
// the merged entity is 'Unknown' as well.
if (Other.Behaviour == State::Throwing)
Behaviour = State::Throwing;
else if (Other.Behaviour == State::Unknown && Behaviour == State::NotThrowing)
Behaviour = State::Unknown;
ContainsUnknown = ContainsUnknown || Other.ContainsUnknown;
ThrownExceptions.insert(Other.ThrownExceptions.begin(),
Other.ThrownExceptions.end());
return *this;
}
static bool isBaseOf(const Type *DerivedType, const Type *BaseType) {
const auto *DerivedClass = DerivedType->getAsCXXRecordDecl();
const auto *BaseClass = BaseType->getAsCXXRecordDecl();
if (!DerivedClass || !BaseClass)
return false;
return !DerivedClass->forallBases(
[BaseClass](const CXXRecordDecl *Cur) { return Cur != BaseClass; });
}
bool ExceptionAnalyzer::ExceptionInfo::filterByCatch(const Type *BaseClass) {
llvm::SmallVector<const Type *, 8> TypesToDelete;
for (const Type *T : ThrownExceptions) {
if (T == BaseClass || isBaseOf(T, BaseClass))
TypesToDelete.push_back(T);
}
for (const Type *T : TypesToDelete)
ThrownExceptions.erase(T);
reevaluateBehaviour();
return TypesToDelete.size() > 0;
}
ExceptionAnalyzer::ExceptionInfo &
ExceptionAnalyzer::ExceptionInfo::filterIgnoredExceptions(
const llvm::StringSet<> &IgnoredTypes, bool IgnoreBadAlloc) {
llvm::SmallVector<const Type *, 8> TypesToDelete;
// Note: Using a 'SmallSet' with 'llvm::remove_if()' is not possible.
// Therefore this slightly hacky implementation is required.
for (const Type *T : ThrownExceptions) {
if (const auto *TD = T->getAsTagDecl()) {
if (TD->getDeclName().isIdentifier()) {
if ((IgnoreBadAlloc &&
(TD->getName() == "bad_alloc" && TD->isInStdNamespace())) ||
(IgnoredTypes.count(TD->getName()) > 0))
TypesToDelete.push_back(T);
}
}
}
for (const Type *T : TypesToDelete)
ThrownExceptions.erase(T);
reevaluateBehaviour();
return *this;
}
void ExceptionAnalyzer::ExceptionInfo::clear() {
Behaviour = State::NotThrowing;
ContainsUnknown = false;
ThrownExceptions.clear();
}
void ExceptionAnalyzer::ExceptionInfo::reevaluateBehaviour() {
if (ThrownExceptions.size() == 0)
if (ContainsUnknown)
Behaviour = State::Unknown;
else
Behaviour = State::NotThrowing;
else
Behaviour = State::Throwing;
}
ExceptionAnalyzer::ExceptionInfo ExceptionAnalyzer::throwsException(
const FunctionDecl *Func,
llvm::SmallSet<const FunctionDecl *, 32> &CallStack) {
if (CallStack.count(Func))
return ExceptionInfo::createNonThrowing();
if (const Stmt *Body = Func->getBody()) {
CallStack.insert(Func);
ExceptionInfo Result =
throwsException(Body, ExceptionInfo::Throwables(), CallStack);
CallStack.erase(Func);
return Result;
}
auto Result = ExceptionInfo::createUnknown();
if (const auto *FPT = Func->getType()->getAs<FunctionProtoType>()) {
for (const QualType Ex : FPT->exceptions())
Result.registerException(Ex.getTypePtr());
}
return Result;
}
/// Analyzes a single statment on it's throwing behaviour. This is in principle
/// possible except some 'Unknown' functions are called.
ExceptionAnalyzer::ExceptionInfo ExceptionAnalyzer::throwsException(
const Stmt *St, const ExceptionInfo::Throwables &Caught,
llvm::SmallSet<const FunctionDecl *, 32> &CallStack) {
auto Results = ExceptionInfo::createNonThrowing();
if (!St)
return Results;
if (const auto *Throw = dyn_cast<CXXThrowExpr>(St)) {
if (const auto *ThrownExpr = Throw->getSubExpr()) {
const auto *ThrownType =
ThrownExpr->getType()->getUnqualifiedDesugaredType();
if (ThrownType->isReferenceType())
ThrownType = ThrownType->castAs<ReferenceType>()
->getPointeeType()
->getUnqualifiedDesugaredType();
Results.registerException(
ThrownExpr->getType()->getUnqualifiedDesugaredType());
} else
// A rethrow of a caught exception happens which makes it possible
// to throw all exception that are caught in the 'catch' clause of
// the parent try-catch block.
Results.registerExceptions(Caught);
} else if (const auto *Try = dyn_cast<CXXTryStmt>(St)) {
ExceptionInfo Uncaught =
throwsException(Try->getTryBlock(), Caught, CallStack);
for (unsigned i = 0; i < Try->getNumHandlers(); ++i) {
const CXXCatchStmt *Catch = Try->getHandler(i);
// Everything is catched through 'catch(...)'.
if (!Catch->getExceptionDecl()) {
ExceptionInfo Rethrown = throwsException(
Catch->getHandlerBlock(), Uncaught.getExceptionTypes(), CallStack);
Results.merge(Rethrown);
Uncaught.clear();
} else {
const auto *CaughtType =
Catch->getCaughtType()->getUnqualifiedDesugaredType();
if (CaughtType->isReferenceType()) {
CaughtType = CaughtType->castAs<ReferenceType>()
->getPointeeType()
->getUnqualifiedDesugaredType();
}
// If the caught exception will catch multiple previously potential
// thrown types (because it's sensitive to inheritance) the throwing
// situation changes. First of all filter the exception types and
// analyze if the baseclass-exception is rethrown.
if (Uncaught.filterByCatch(CaughtType)) {
ExceptionInfo::Throwables CaughtExceptions;
CaughtExceptions.insert(CaughtType);
ExceptionInfo Rethrown = throwsException(Catch->getHandlerBlock(),
CaughtExceptions, CallStack);
Results.merge(Rethrown);
}
}
}
Results.merge(Uncaught);
} else if (const auto *Call = dyn_cast<CallExpr>(St)) {
if (const FunctionDecl *Func = Call->getDirectCallee()) {
ExceptionInfo Excs = throwsException(Func, CallStack);
Results.merge(Excs);
}
} else {
for (const Stmt *Child : St->children()) {
ExceptionInfo Excs = throwsException(Child, Caught, CallStack);
Results.merge(Excs);
}
}
return Results;
}
ExceptionAnalyzer::ExceptionInfo
ExceptionAnalyzer::analyzeImpl(const FunctionDecl *Func) {
ExceptionInfo ExceptionList;
// Check if the function has already been analyzed and reuse that result.
if (FunctionCache.count(Func) == 0) {
llvm::SmallSet<const FunctionDecl *, 32> CallStack;
ExceptionList = throwsException(Func, CallStack);
// Cache the result of the analysis. This is done prior to filtering
// because it is best to keep as much information as possible.
// The results here might be relevant to different analysis passes
// with different needs as well.
FunctionCache.insert(std::make_pair(Func, ExceptionList));
} else
ExceptionList = FunctionCache[Func];
return ExceptionList;
}
ExceptionAnalyzer::ExceptionInfo
ExceptionAnalyzer::analyzeImpl(const Stmt *Stmt) {
llvm::SmallSet<const FunctionDecl *, 32> CallStack;
return throwsException(Stmt, ExceptionInfo::Throwables(), CallStack);
}
template <typename T>
ExceptionAnalyzer::ExceptionInfo
ExceptionAnalyzer::analyzeDispatch(const T *Node) {
ExceptionInfo ExceptionList = analyzeImpl(Node);
if (ExceptionList.getBehaviour() == State::NotThrowing ||
ExceptionList.getBehaviour() == State::Unknown)
return ExceptionList;
// Remove all ignored exceptions from the list of exceptions that can be
// thrown.
ExceptionList.filterIgnoredExceptions(IgnoredExceptions, IgnoreBadAlloc);
return ExceptionList;
}
ExceptionAnalyzer::ExceptionInfo
ExceptionAnalyzer::analyze(const FunctionDecl *Func) {
return analyzeDispatch(Func);
}
ExceptionAnalyzer::ExceptionInfo
ExceptionAnalyzer::analyze(const Stmt *Stmt) {
return analyzeDispatch(Stmt);
}
} // namespace utils
} // namespace tidy
} // namespace clang
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