CIRGenException.cpp

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//===--- CIRGenException.cpp - Emit CIR Code for C++ exceptions -*- 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 contains code dealing with C++ exception related code generation.
//
//===----------------------------------------------------------------------===//
 
#include "CIRGenCXXABI.h"
#include "CIRGenFunction.h"
#include "mlir/IR/Block.h"
#include "mlir/IR/Location.h"
 
#include "clang/CIR/MissingFeatures.h"
#include "llvm/Support/SaveAndRestore.h"
 
using namespace clang;
using namespace clang::CIRGen;
 
const EHPersonality EHPersonality::GNU_C = {"__gcc_personality_v0", nullptr};
const EHPersonality EHPersonality::GNU_C_SJLJ = {"__gcc_personality_sj0",
                                                 nullptr};
const EHPersonality EHPersonality::GNU_C_SEH = {"__gcc_personality_seh0",
                                                nullptr};
const EHPersonality EHPersonality::NeXT_ObjC = {"__objc_personality_v0",
                                                nullptr};
const EHPersonality EHPersonality::GNU_CPlusPlus = {"__gxx_personality_v0",
                                                    nullptr};
const EHPersonality EHPersonality::GNU_CPlusPlus_SJLJ = {
    "__gxx_personality_sj0", nullptr};
const EHPersonality EHPersonality::GNU_CPlusPlus_SEH = {
    "__gxx_personality_seh0", nullptr};
const EHPersonality EHPersonality::GNU_ObjC = {"__gnu_objc_personality_v0",
                                               "objc_exception_throw"};
const EHPersonality EHPersonality::GNU_ObjC_SJLJ = {
    "__gnu_objc_personality_sj0", "objc_exception_throw"};
const EHPersonality EHPersonality::GNU_ObjC_SEH = {
    "__gnu_objc_personality_seh0", "objc_exception_throw"};
const EHPersonality EHPersonality::GNU_ObjCXX = {
    "__gnustep_objcxx_personality_v0", nullptr};
const EHPersonality EHPersonality::GNUstep_ObjC = {
    "__gnustep_objc_personality_v0", nullptr};
const EHPersonality EHPersonality::MSVC_except_handler = {"_except_handler3",
                                                          nullptr};
const EHPersonality EHPersonality::MSVC_C_specific_handler = {
    "__C_specific_handler", nullptr};
const EHPersonality EHPersonality::MSVC_CxxFrameHandler3 = {
    "__CxxFrameHandler3", nullptr};
const EHPersonality EHPersonality::GNU_Wasm_CPlusPlus = {
    "__gxx_wasm_personality_v0", nullptr};
const EHPersonality EHPersonality::XL_CPlusPlus = {"__xlcxx_personality_v1",
                                                   nullptr};
const EHPersonality EHPersonality::ZOS_CPlusPlus = {"__zos_cxx_personality_v2",
                                                    nullptr};
 
static const EHPersonality &getCPersonality(const TargetInfo &target,
                                            const CodeGenOptions &cgOpts) {
  const llvm::Triple &triple = target.getTriple();
  if (triple.isWindowsMSVCEnvironment())
    return EHPersonality::MSVC_CxxFrameHandler3;
  if (cgOpts.hasSjLjExceptions())
    return EHPersonality::GNU_C_SJLJ;
  if (cgOpts.hasDWARFExceptions())
    return EHPersonality::GNU_C;
  if (cgOpts.hasSEHExceptions())
    return EHPersonality::GNU_C_SEH;
  return EHPersonality::GNU_C;
}
 
static const EHPersonality &getObjCPersonality(const TargetInfo &target,
                                               const LangOptions &langOpts,
                                               const CodeGenOptions &cgOpts) {
  const llvm::Triple &triple = target.getTriple();
  if (triple.isWindowsMSVCEnvironment())
    return EHPersonality::MSVC_CxxFrameHandler3;
 
  switch (langOpts.ObjCRuntime.getKind()) {
  case ObjCRuntime::FragileMacOSX:
    return getCPersonality(target, cgOpts);
  case ObjCRuntime::MacOSX:
  case ObjCRuntime::iOS:
  case ObjCRuntime::WatchOS:
    return EHPersonality::NeXT_ObjC;
  case ObjCRuntime::GNUstep:
    if (langOpts.ObjCRuntime.getVersion() >= VersionTuple(1, 7))
      return EHPersonality::GNUstep_ObjC;
    [[fallthrough]];
  case ObjCRuntime::GCC:
  case ObjCRuntime::ObjFW:
    if (cgOpts.hasSjLjExceptions())
      return EHPersonality::GNU_ObjC_SJLJ;
    if (cgOpts.hasSEHExceptions())
      return EHPersonality::GNU_ObjC_SEH;
    return EHPersonality::GNU_ObjC;
  }
  llvm_unreachable("bad runtime kind");
}
 
static const EHPersonality &getCXXPersonality(const TargetInfo &target,
                                              const CodeGenOptions &cgOpts) {
  const llvm::Triple &triple = target.getTriple();
  if (triple.isWindowsMSVCEnvironment())
    return EHPersonality::MSVC_CxxFrameHandler3;
  if (triple.isOSAIX())
    return EHPersonality::XL_CPlusPlus;
  if (cgOpts.hasSjLjExceptions())
    return EHPersonality::GNU_CPlusPlus_SJLJ;
  if (cgOpts.hasDWARFExceptions())
    return EHPersonality::GNU_CPlusPlus;
  if (cgOpts.hasSEHExceptions())
    return EHPersonality::GNU_CPlusPlus_SEH;
  if (cgOpts.hasWasmExceptions())
    return EHPersonality::GNU_Wasm_CPlusPlus;
  return EHPersonality::GNU_CPlusPlus;
}
 
/// Determines the personality function to use when both C++
/// and Objective-C exceptions are being caught.
static const EHPersonality &getObjCXXPersonality(const TargetInfo &target,
                                                 const LangOptions &langOpts,
                                                 const CodeGenOptions &cgOpts) {
  if (target.getTriple().isWindowsMSVCEnvironment())
    return EHPersonality::MSVC_CxxFrameHandler3;
 
  switch (langOpts.ObjCRuntime.getKind()) {
  // In the fragile ABI, just use C++ exception handling and hope
  // they're not doing crazy exception mixing.
  case ObjCRuntime::FragileMacOSX:
    return getCXXPersonality(target, cgOpts);
 
  // The ObjC personality defers to the C++ personality for non-ObjC
  // handlers.  Unlike the C++ case, we use the same personality
  // function on targets using (backend-driven) SJLJ EH.
  case ObjCRuntime::MacOSX:
  case ObjCRuntime::iOS:
  case ObjCRuntime::WatchOS:
    return getObjCPersonality(target, langOpts, cgOpts);
 
  case ObjCRuntime::GNUstep:
    return EHPersonality::GNU_ObjCXX;
 
  // The GCC runtime's personality function inherently doesn't support
  // mixed EH.  Use the ObjC personality just to avoid returning null.
  case ObjCRuntime::GCC:
  case ObjCRuntime::ObjFW:
    return getObjCPersonality(target, langOpts, cgOpts);
  }
  llvm_unreachable("bad runtime kind");
}
 
static const EHPersonality &getSEHPersonalityMSVC(const llvm::Triple &triple) {
  return triple.getArch() == llvm::Triple::x86
             ? EHPersonality::MSVC_except_handler
             : EHPersonality::MSVC_C_specific_handler;
}
 
const EHPersonality &EHPersonality::get(CIRGenModule &cgm,
                                        const FunctionDecl *fd) {
  const llvm::Triple &triple = cgm.getTarget().getTriple();
  const LangOptions &langOpts = cgm.getLangOpts();
  const CodeGenOptions &cgOpts = cgm.getCodeGenOpts();
  const TargetInfo &target = cgm.getTarget();
 
  // Functions using SEH get an SEH personality.
  if (fd && fd->usesSEHTry())
    return getSEHPersonalityMSVC(triple);
 
  if (langOpts.ObjC) {
    return langOpts.CPlusPlus ? getObjCXXPersonality(target, langOpts, cgOpts)
                              : getObjCPersonality(target, langOpts, cgOpts);
  }
  return langOpts.CPlusPlus ? getCXXPersonality(target, cgOpts)
                            : getCPersonality(target, cgOpts);
}
 
const EHPersonality &EHPersonality::get(CIRGenFunction &cgf) {
  const auto *fg = cgf.curCodeDecl;
  // For outlined finallys and filters, use the SEH personality in case they
  // contain more SEH. This mostly only affects finallys. Filters could
  // hypothetically use gnu statement expressions to sneak in nested SEH.
  fg = fg ? fg : cgf.curSEHParent.getDecl();
  return get(cgf.cgm, dyn_cast_or_null<FunctionDecl>(fg));
}
 
static llvm::StringRef getPersonalityFn(CIRGenModule &cgm,
                                        const EHPersonality &personality) {
  // Create the personality function type: i32 (...)
  mlir::Type i32Ty = cgm.getBuilder().getI32Type();
  auto funcTy = cir::FuncType::get({}, i32Ty, /*isVarArg=*/true);
 
  cir::FuncOp personalityFn = cgm.createRuntimeFunction(
      funcTy, personality.personalityFn, {}, /*isLocal=*/true);
 
  return personalityFn.getSymName();
}
 
void CIRGenFunction::emitCXXThrowExpr(const CXXThrowExpr *e) {
  const llvm::Triple &triple = getTarget().getTriple();
  if (cgm.getLangOpts().OpenMPIsTargetDevice &&
      (triple.isNVPTX() || triple.isAMDGCN())) {
    cgm.errorNYI("emitCXXThrowExpr OpenMP with NVPTX or AMDGCN Triples");
    return;
  }
 
  if (const Expr *subExpr = e->getSubExpr()) {
    QualType throwType = subExpr->getType();
    if (throwType->isObjCObjectPointerType()) {
      cgm.errorNYI("emitCXXThrowExpr ObjCObjectPointerType");
      return;
    }
 
    cgm.getCXXABI().emitThrow(*this, e);
    return;
  }
 
  cgm.getCXXABI().emitRethrow(*this, /*isNoReturn=*/true);
}
 
void CIRGenFunction::emitAnyExprToExn(const Expr *e, Address addr) {
  // Make sure the exception object is cleaned up if there's an
  // exception during initialization.
  assert(!cir::MissingFeatures::ehCleanupScope());
 
  // __cxa_allocate_exception returns a void*;  we need to cast this
  // to the appropriate type for the object.
  mlir::Type ty = convertTypeForMem(e->getType());
  Address typedAddr = addr.withElementType(builder, ty);
 
  // From LLVM's codegen:
  // FIXME: this isn't quite right!  If there's a final unelided call
  // to a copy constructor, then according to [except.terminate]p1 we
  // must call std::terminate() if that constructor throws, because
  // technically that copy occurs after the exception expression is
  // evaluated but before the exception is caught.  But the best way
  // to handle that is to teach EmitAggExpr to do the final copy
  // differently if it can't be elided.
  emitAnyExprToMem(e, typedAddr, e->getType().getQualifiers(),
                   /*isInitializer=*/true);
 
  // Deactivate the cleanup block.
  assert(!cir::MissingFeatures::ehCleanupScope());
}
 
void CIRGenFunction::addCatchHandlerAttr(
    const CXXCatchStmt *catchStmt, SmallVector<mlir::Attribute> &handlerAttrs) {
  mlir::Location catchLoc = getLoc(catchStmt->getBeginLoc());
 
  if (catchStmt->getExceptionDecl()) {
    // FIXME: Dropping the reference type on the type into makes it
    // impossible to correctly implement catch-by-reference
    // semantics for pointers.  Unfortunately, this is what all
    // existing compilers do, and it's not clear that the standard
    // personality routine is capable of doing this right.  See C++ DR 388:
    //   http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#388
    Qualifiers caughtTypeQuals;
    QualType caughtType = cgm.getASTContext().getUnqualifiedArrayType(
        catchStmt->getCaughtType().getNonReferenceType(), caughtTypeQuals);
    if (caughtType->isObjCObjectPointerType()) {
      cgm.errorNYI("addCatchHandlerAttr: caughtType ObjCObjectPointerType");
      return;
    }
 
    CatchTypeInfo typeInfo = cgm.getCXXABI().getAddrOfCXXCatchHandlerType(
        catchLoc, caughtType, catchStmt->getCaughtType());
    handlerAttrs.push_back(typeInfo.rtti);
  } else {
    // No exception decl indicates '...', a catch-all.
    handlerAttrs.push_back(cir::CatchAllAttr::get(&getMLIRContext()));
  }
}
 
namespace {
struct CallEndCatch final : EHScopeStack::Cleanup {
  CallEndCatch(mlir::Value catchToken) : catchToken(catchToken) {}
  mlir::Value catchToken;
 
  void emit(CIRGenFunction &cgf, Flags flags) override {
    cir::EndCatchOp::create(cgf.getBuilder(), *cgf.currSrcLoc, catchToken);
    cir::YieldOp::create(cgf.getBuilder(), *cgf.currSrcLoc);
  }
};
} // namespace
 
static mlir::Value callBeginCatch(CIRGenFunction &cgf, mlir::Value ehToken,
                                  mlir::Type exnPtrTy) {
  auto catchTokenTy = cir::CatchTokenType::get(cgf.getBuilder().getContext());
  auto beginCatch = cir::BeginCatchOp::create(cgf.getBuilder(),
                                              cgf.getBuilder().getUnknownLoc(),
                                              catchTokenTy, exnPtrTy, ehToken);
 
  cgf.ehStack.pushCleanup<CallEndCatch>(NormalAndEHCleanup,
                                        beginCatch.getCatchToken());
 
  return beginCatch.getExnPtr();
}
 
/// A "special initializer" callback for initializing a catch
/// parameter during catch initialization.
static void initCatchParam(CIRGenFunction &cgf, CIRGenBuilderTy &builder,
                           mlir::Value ehToken, const VarDecl &catchParam,
                           SourceLocation loc) {
  CanQualType catchType =
      cgf.cgm.getASTContext().getCanonicalType(catchParam.getType());
  cir::InitCatchKind kind;
 
  // If we're catching by reference, we can just cast the object
  // pointer to the appropriate pointer.
  if (isa<ReferenceType>(catchType)) {
    kind = cir::InitCatchKind::Reference;
  } else {
    cir::TypeEvaluationKind tek = cgf.getEvaluationKind(catchType);
    if (tek == cir::TEK_Aggregate) {
      assert(isa<RecordType>(catchType) && "unexpected catch type!");
      const Expr *copyExpr = catchParam.getInit();
      kind = !copyExpr ? cir::InitCatchKind::TrivialCopy
                       : cir::InitCatchKind::NonTrivialCopy;
    } else {
      // Scalars and complexes.
      if (catchType->hasPointerRepresentation()) {
        switch (catchType.getQualifiers().getObjCLifetime()) {
        case Qualifiers::OCL_Weak:
        case Qualifiers::OCL_Strong:
          kind = cir::InitCatchKind::Objc;
          break;
 
        case Qualifiers::OCL_ExplicitNone:
        case Qualifiers::OCL_Autoreleasing:
        case Qualifiers::OCL_None:
          kind = cir::InitCatchKind::Pointer;
          break;
        }
      } else {
        kind = cir::InitCatchKind::Scalar;
      }
    }
  }
 
  mlir::Value exnPtr = callBeginCatch(cgf, ehToken, builder.getVoidPtrTy());
  CIRGenFunction::AutoVarEmission var = cgf.emitAutoVarAlloca(catchParam);
  cir::InitCatchParamOp::create(builder, cgf.getLoc(loc), exnPtr,
                                var.getAllocatedAddress().getPointer(), kind);
  cgf.emitAutoVarCleanups(var);
}
 
/// Begins a catch statement by initializing the catch variable and
/// calling __cxa_begin_catch.
void CIRGenFunction::emitBeginCatch(const CXXCatchStmt *catchStmt,
                                    mlir::Value ehToken) {
  // We have to be very careful with the ordering of cleanups here:
  //   C++ [except.throw]p4:
  //     The destruction [of the exception temporary] occurs
  //     immediately after the destruction of the object declared in
  //     the exception-declaration in the handler.
  //
  // So the precise ordering is:
  //   1.  Construct catch variable.
  //   2.  begin_catch
  //   3.  Enter CallEndCatch cleanup
  //   4.  Enter dtor cleanup
  //
  VarDecl *catchParam = catchStmt->getExceptionDecl();
  if (!catchParam) {
    callBeginCatch(*this, ehToken, builder.getVoidPtrTy());
    return;
  }
 
  // Emit the local. Make sure the alloca's superseed the current scope, since
  // these are going to be consumed by `cir.catch`, which is not within the
  // current scope.
  initCatchParam(*this, builder, ehToken, *catchParam,
                 catchStmt->getBeginLoc());
}
 
mlir::LogicalResult
CIRGenFunction::emitCXXTryStmt(const CXXTryStmt &s,
                               cxxTryBodyEmitter &bodyCallback) {
  mlir::Location loc = getLoc(s.getSourceRange());
 
  // Create a scope to hold try local storage for catch params.
  mlir::OpBuilder::InsertPoint scopeIP;
  cir::ScopeOp::create(
      builder, loc,
      /*scopeBuilder=*/[&](mlir::OpBuilder &b, mlir::Location loc) {
        scopeIP = builder.saveInsertionPoint();
      });
 
  // Set personality function if not already set
  auto funcOp = mlir::cast<cir::FuncOp>(curFn);
  if (!funcOp.getPersonality())
    funcOp.setPersonality(getPersonalityFn(cgm, EHPersonality::get(*this)));
 
  mlir::OpBuilder::InsertionGuard guard(builder);
  builder.restoreInsertionPoint(scopeIP);
 
  const llvm::Triple &t = getTarget().getTriple();
  // If we encounter a try statement on in an OpenMP target region offloaded
  // to a GPU, we treat it as a basic block.
  const bool isTargetDevice =
      (cgm.getLangOpts().OpenMPIsTargetDevice && (t.isNVPTX() || t.isAMDGCN()));
  if (isTargetDevice) {
    cgm.errorNYI("emitCXXTryStmt: OpenMP target region offloaded to GPU");
    return mlir::success();
  }
 
  mlir::Location tryLoc = getLoc(s.getBeginLoc());
  SmallVector<mlir::Attribute> handlerAttrs;
 
  CIRGenFunction::LexicalScope tryBodyScope{*this, tryLoc,
                                            builder.getInsertionBlock()};
 
  if (getLangOpts().EHAsynch) {
    cgm.errorNYI("enterCXXTryStmt: EHAsynch");
    return mlir::failure();
  }
 
  // Create the try operation.
  mlir::LogicalResult tryRes = mlir::success();
  auto tryOp = cir::TryOp::create(
      builder, tryLoc,
      /*tryBuilder=*/
      [&](mlir::OpBuilder &b, mlir::Location loc) {
        // Create a RunCleanupsScope that allows us to apply any cleanups that
        // are created for statements within the try body before exiting the
        // try body.
        RunCleanupsScope tryBodyCleanups(*this);
        if (bodyCallback(*this).failed())
          tryRes = mlir::failure();
        tryBodyCleanups.forceCleanup();
        cir::YieldOp::create(builder, loc);
      },
      /*handlersBuilder=*/
      [&](mlir::OpBuilder &b, mlir::Location loc,
          mlir::OperationState &result) {
        mlir::OpBuilder::InsertionGuard guard(b);
        bool hasCatchAll = false;
        unsigned numHandlers = s.getNumHandlers();
        mlir::Type ehTokenTy = cir::EhTokenType::get(&getMLIRContext());
        for (unsigned i = 0; i != numHandlers; ++i) {
          const CXXCatchStmt *catchStmt = s.getHandler(i);
          if (!catchStmt->getExceptionDecl())
            hasCatchAll = true;
          mlir::Region *region = result.addRegion();
          builder.createBlock(region, /*insertPt=*/{}, {ehTokenTy}, {loc});
          addCatchHandlerAttr(catchStmt, handlerAttrs);
        }
        if (!hasCatchAll) {
          // Create unwind region.
          mlir::Region *region = result.addRegion();
          mlir::Block *unwindBlock =
              builder.createBlock(region, /*insertPt=*/{}, {ehTokenTy}, {loc});
          cir::ResumeOp::create(builder, loc, unwindBlock->getArgument(0));
          handlerAttrs.push_back(cir::UnwindAttr::get(&getMLIRContext()));
        }
      });
 
  if (tryRes.failed())
    return mlir::failure();
 
  // Add final array of clauses into TryOp.
  tryOp.setHandlerTypesAttr(
      mlir::ArrayAttr::get(&getMLIRContext(), handlerAttrs));
 
  // Emit the catch handler bodies. This has to be done after the try op is
  // created and in place so that we can find the insertion point for the
  // catch parameter alloca.
  unsigned numHandlers = s.getNumHandlers();
  for (unsigned i = 0; i != numHandlers; ++i) {
    const CXXCatchStmt *catchStmt = s.getHandler(i);
    mlir::Region *handler = &tryOp.getHandlerRegions()[i];
    mlir::Location handlerLoc = getLoc(catchStmt->getCatchLoc());
 
    mlir::OpBuilder::InsertionGuard guard(builder);
    builder.setInsertionPointToStart(&handler->front());
 
    // Get the !cir.eh_token block argument from the handler region.
    mlir::Value ehToken = handler->front().getArgument(0);
 
    // Enter a cleanup scope, including the catch variable and the
    // end-catch.
    RunCleanupsScope handlerScope(*this);
 
    // Initialize the catch variable.
    // TODO(cir): Move this out of CXXABI.
    assert(!cir::MissingFeatures::currentFuncletPad());
    emitBeginCatch(catchStmt, ehToken);
 
    // Emit the PGO counter increment.
    assert(!cir::MissingFeatures::incrementProfileCounter());
 
    // Perform the body of the catch.
    [[maybe_unused]] mlir::LogicalResult emitResult =
        emitStmt(catchStmt->getHandlerBlock(), /*useCurrentScope=*/true);
    assert(emitResult.succeeded() && "failed to emit catch handler block");
 
    // [except.handle]p11:
    //   The currently handled exception is rethrown if control
    //   reaches the end of a handler of the function-try-block of a
    //   constructor or destructor.
 
    // TODO(cir): Handle implicit rethrow?
 
    // Fall out through the catch cleanups.
    handlerScope.forceCleanup();
 
    mlir::Block *block = &handler->getBlocks().back();
    if (block->empty() ||
        !block->back().hasTrait<mlir::OpTrait::IsTerminator>()) {
      mlir::OpBuilder::InsertionGuard guard(builder);
      builder.setInsertionPointToEnd(block);
      builder.createYield(handlerLoc);
    }
  }
 
  return mlir::success();
}
 
mlir::LogicalResult CIRGenFunction::emitCXXTryStmt(const CXXTryStmt &s) {
  if (s.getTryBlock()->body_empty())
    return mlir::LogicalResult::success();
 
  struct simpleTryBodyEmitter final : cxxTryBodyEmitter {
    const clang::CXXTryStmt &s;
    simpleTryBodyEmitter(const clang::CXXTryStmt &s) : s(s) {}
 
    mlir::LogicalResult operator()(CIRGenFunction &cgf) override {
      return cgf.emitStmt(s.getTryBlock(), /*useCurrentScope=*/true);
    }
    ~simpleTryBodyEmitter() override = default;
  };
 
  simpleTryBodyEmitter emitter{s};
 
  return emitCXXTryStmt(s, emitter);
}
 
// in classic codegen this function is mapping to `isInvokeDest` previously
// and currently it's mapping to the conditions that performs early returns in
// `getInvokeDestImpl`, in CIR we need the condition to know if the EH scope
// may throw exception or now.
bool CIRGenFunction::isCatchOrCleanupRequired() {
  // If exceptions are disabled/ignored and SEH is not in use, then there is
  // no invoke destination. SEH "works" even if exceptions are off. In
  // practice, this means that C++ destructors and other EH cleanups don't
  // run, which is consistent with MSVC's behavior, except in the presence of
  // -EHa
  const LangOptions &lo = cgm.getLangOpts();
  if (!lo.Exceptions || lo.IgnoreExceptions) {
    if (!lo.Borland && !lo.MicrosoftExt)
      return false;
    cgm.errorNYI("isInvokeDest: no exceptions or ignore exception");
    return false;
  }
 
  // CUDA device code doesn't have exceptions.
  if (lo.CUDA && lo.CUDAIsDevice)
    return false;
 
  return ehStack.requiresCatchOrCleanup();
}