[llvm] r278974 - ADT: Remove UB in ilist (and use a circular linked list)
Duncan P. N. Exon Smith via llvm-commits
llvm-commits at lists.llvm.org
Thu Aug 18 17:14:05 PDT 2016
Hi Diana, any update? Are you able to test pre-commit, or should I just commit and let the bots do the work?
> On 2016-Aug-18, at 11:09, Duncan P. N. Exon Smith via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>
> Hi Diana,
>
> I fixed PR29035 in r279104. Are you able to test that revision with r278974 cherry-picked on top to be sure the assertion isn't firing elsewhere?
>
> Thanks,
> Duncan
>
>> On 2016-Aug-18, at 06:19, Duncan Exon Smith via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>>
>> Please attach the reproducer mentioned in the log message:
>>
>> clang-4.0: note: diagnostic msg: PLEASE submit a bug report to http://llvm.org/bugs/ and include the crash backtrace, preprocessed source, and associated run script.
>> clang-4.0: note: diagnostic msg:
>> ********************
>> PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
>> Preprocessed source(s) and associated run script(s) are located at:
>> clang-4.0: note: diagnostic msg: /tmp/gtest-all-78e9e5.cpp
>> clang-4.0: note: diagnostic msg: /tmp/gtest-all-78e9e5.sh
>> clang-4.0: note: diagnostic msg:
>> ********************
>>
>> -- dpnes
>>
>> On Aug 18, 2016, at 04:32, Diana Picus <diana.picus at linaro.org> wrote:
>>
>>> Hi,
>>>
>>> I had to revert this because it was breaking some of the bots. I also
>>> reverted r279012 because it was in the way (and it looked like a fixup
>>> for this revision anyway).
>>> I've attached a log of the failure to this bug:
>>> https://llvm.org/bugs/show_bug.cgi?id=29035
>>> Please let me know if you need anything else to debug this.
>>>
>>> Thanks,
>>> Diana
>>>
>>>
>>>
>>> On 17 August 2016 at 23:44, Duncan P. N. Exon Smith via llvm-commits
>>> <llvm-commits at lists.llvm.org> wrote:
>>>> Author: dexonsmith
>>>> Date: Wed Aug 17 15:44:33 2016
>>>> New Revision: 278974
>>>>
>>>> URL: http://llvm.org/viewvc/llvm-project?rev=278974&view=rev
>>>> Log:
>>>> ADT: Remove UB in ilist (and use a circular linked list)
>>>>
>>>> This removes the undefined behaviour (UB) in ilist/ilist_node/etc.,
>>>> mainly by removing (gutting) the ilist_sentinel_traits customization
>>>> point and canonicalizing on a single, efficient memory layout. This
>>>> fixes PR26753.
>>>>
>>>> The new ilist is a doubly-linked circular list.
>>>> - ilist_node_base has two ilist_node_base*: Next and Prev. Size-of: two
>>>> pointers.
>>>> - ilist_node<T> (size-of: two pointers) is a type-safe wrapper around
>>>> ilist_node_base.
>>>> - ilist_iterator<T> (size-of: two pointers) operates on an
>>>> ilist_node<T>*, and downcasts to T* on dereference.
>>>> - ilist_sentinel<T> (size-of: two pointers) is a wrapper around
>>>> ilist_node<T> that has some extra API for list management.
>>>> - ilist<T> (size-of: two pointers) has an ilist_sentinel<T>, whose
>>>> address is returned for end().
>>>>
>>>> The new memory layout matches ilist_half_embedded_sentinel_traits<T>
>>>> exactly. The Head pointer that previously lived in ilist<T> is
>>>> effectively glued to the ilist_half_node<T> that lived in
>>>> ilist_half_embedded_sentinel_traits<T>, becoming the Next and Prev in
>>>> the ilist_sentinel_node<T>, respectively. sizeof(ilist<T>) is now the
>>>> size of two pointers, and there is never any additional storage for a
>>>> sentinel.
>>>>
>>>> This is a much simpler design for a doubly-linked list, removing most of
>>>> the corner cases of list manipulation (add, remove, etc.). In follow-up
>>>> commits, I intend to move as many algorithms as possible into a
>>>> non-templated base class (ilist_base) to reduce code size.
>>>>
>>>> Moreover, this fixes the UB in ilist_iterator/getNext/getPrev
>>>> operations. Previously, ilist_iterator<T> operated on a T*, even when
>>>> the sentinel was not of type T (i.e., ilist_embedded_sentinel_traits and
>>>> ilist_half_embedded_sentinel_traits). This added UB to all operations
>>>> involving end(). Now, ilist_iterator<T> operates on an ilist_node<T>*,
>>>> and only downcasts when the full type is guaranteed to be T*.
>>>>
>>>> What did we lose? There used to be a crash (in some configurations) on
>>>> ++end(). Curiously (via UB), ++end() would return begin() for users of
>>>> ilist_half_embedded_sentinel_traits<T>, but otherwise ++end() would
>>>> cause a nice dependable nullptr dereference, crashing instead of a
>>>> possible infinite loop. Options:
>>>> 1. Lose that behaviour.
>>>> 2. Keep it, by stealing a bit from Prev in asserts builds.
>>>> 3. Crash on dereference instead, using the same technique.
>>>>
>>>> Hans convinced me (because of the number of problems this and r278532
>>>> exposed on Windows) that we really need some assertion here, at least in
>>>> the short term. I've opted for #3 since I think it catches more bugs.
>>>>
>>>> I added only a couple of unit tests to root out specific bugs I hit
>>>> during bring-up, but otherwise this is tested implicitly via the
>>>> extensive usage throughout LLVM.
>>>>
>>>> Planned follow-ups:
>>>> - Remove ilist_*sentinel_traits<T>. Here I've just gutted them to
>>>> prevent build failures in sub-projects. Once I stop referring to them
>>>> in sub-projects, I'll come back and delete them.
>>>> - Add ilist_base and move algorithms there.
>>>> - Check and fix move construction and assignment.
>>>>
>>>> Eventually, there are other interesting directions:
>>>> - Rewrite reverse iterators, so that rbegin().getNodePtr()==&*rbegin().
>>>> This allows much simpler logic when erasing elements during a reverse
>>>> traversal.
>>>> - Remove ilist_traits::createNode, by deleting the remaining API that
>>>> creates nodes. Intrusive lists shouldn't be creating nodes
>>>> themselves.
>>>> - Remove ilist_traits::deleteNode, by (1) asserting that lists are empty
>>>> on destruction and (2) changing API that calls it to take a Deleter
>>>> functor (intrusive lists shouldn't be in the memory management
>>>> business).
>>>> - Reconfigure the remaining callback traits (addNodeToList, etc.) to be
>>>> higher-level, pulling out a simple_ilist<T> that is much easier to
>>>> read and understand.
>>>> - Allow tags (e.g., ilist_node<T,tag1> and ilist_node<T,tag2>) so that T
>>>> can be a member of multiple intrusive lists.
>>>>
>>>> Modified:
>>>> llvm/trunk/include/llvm/ADT/ilist.h
>>>> llvm/trunk/include/llvm/ADT/ilist_node.h
>>>> llvm/trunk/unittests/ADT/ilistTest.cpp
>>>>
>>>> Modified: llvm/trunk/include/llvm/ADT/ilist.h
>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/ilist.h?rev=278974&r1=278973&r2=278974&view=diff
>>>> ==============================================================================
>>>> --- llvm/trunk/include/llvm/ADT/ilist.h (original)
>>>> +++ llvm/trunk/include/llvm/ADT/ilist.h Wed Aug 17 15:44:33 2016
>>>> @@ -15,17 +15,16 @@
>>>> // replacement does not provide a constant time size() method, so be careful to
>>>> // use empty() when you really want to know if it's empty.
>>>> //
>>>> -// The ilist class is implemented by allocating a 'tail' node when the list is
>>>> -// created (using ilist_traits<>::createSentinel()). This tail node is
>>>> -// absolutely required because the user must be able to compute end()-1. Because
>>>> -// of this, users of the direct next/prev links will see an extra link on the
>>>> -// end of the list, which should be ignored.
>>>> +// The ilist class is implemented as a circular list. The list itself contains
>>>> +// a sentinel node, whose Next points at begin() and whose Prev points at
>>>> +// rbegin(). The sentinel node itself serves as end() and rend().
>>>> //
>>>> //===----------------------------------------------------------------------===//
>>>>
>>>> #ifndef LLVM_ADT_ILIST_H
>>>> #define LLVM_ADT_ILIST_H
>>>>
>>>> +#include "llvm/ADT/ilist_node.h"
>>>> #include "llvm/Support/Compiler.h"
>>>> #include <algorithm>
>>>> #include <cassert>
>>>> @@ -38,37 +37,42 @@ namespace llvm {
>>>> template<typename NodeTy, typename Traits> class iplist;
>>>> template<typename NodeTy> class ilist_iterator;
>>>>
>>>> -/// An access class for next/prev on ilist_nodes.
>>>> +/// An access class for ilist_node private API.
>>>> ///
>>>> /// This gives access to the private parts of ilist nodes. Nodes for an ilist
>>>> /// should friend this class if they inherit privately from ilist_node.
>>>> ///
>>>> -/// It's strongly discouraged to *use* this class outside of ilist
>>>> +/// It's strongly discouraged to *use* this class outside of the ilist
>>>> /// implementation.
>>>> struct ilist_node_access {
>>>> - template <typename NodeTy> static NodeTy *getPrev(NodeTy *N) {
>>>> + template <typename T> static ilist_node<T> *getNodePtr(T *N) { return N; }
>>>> + template <typename T> static const ilist_node<T> *getNodePtr(const T *N) {
>>>> + return N;
>>>> + }
>>>> +
>>>> + template <typename T> static ilist_node<T> *getPrev(ilist_node<T> *N) {
>>>> return N->getPrev();
>>>> }
>>>> - template <typename NodeTy> static NodeTy *getNext(NodeTy *N) {
>>>> + template <typename T> static ilist_node<T> *getNext(ilist_node<T> *N) {
>>>> return N->getNext();
>>>> }
>>>> - template <typename NodeTy> static const NodeTy *getPrev(const NodeTy *N) {
>>>> + template <typename T> static const ilist_node<T> *getPrev(const ilist_node<T> *N) {
>>>> return N->getPrev();
>>>> }
>>>> - template <typename NodeTy> static const NodeTy *getNext(const NodeTy *N) {
>>>> + template <typename T> static const ilist_node<T> *getNext(const ilist_node<T> *N) {
>>>> return N->getNext();
>>>> }
>>>>
>>>> - template <typename NodeTy> static void setPrev(NodeTy *N, NodeTy *Prev) {
>>>> + template <typename T> static void setPrev(ilist_node<T> *N, ilist_node<T> *Prev) {
>>>> N->setPrev(Prev);
>>>> }
>>>> - template <typename NodeTy> static void setNext(NodeTy *N, NodeTy *Next) {
>>>> + template <typename T> static void setNext(ilist_node<T> *N, ilist_node<T> *Next) {
>>>> N->setNext(Next);
>>>> }
>>>> - template <typename NodeTy> static void setPrev(NodeTy *N, std::nullptr_t) {
>>>> + template <typename T> static void setPrev(ilist_node<T> *N, std::nullptr_t) {
>>>> N->setPrev(nullptr);
>>>> }
>>>> - template <typename NodeTy> static void setNext(NodeTy *N, std::nullptr_t) {
>>>> + template <typename T> static void setNext(ilist_node<T> *N, std::nullptr_t) {
>>>> N->setNext(nullptr);
>>>> }
>>>> };
>>>> @@ -93,111 +97,31 @@ template <class TraitsT, class NodeT> st
>>>> static const bool value = sizeof(hasGetNext<TraitsT>(nullptr)) == sizeof(Yes);
>>>> };
>>>>
>>>> -} // end namespace ilist_detail
>>>> -
>>>> -template<typename NodeTy>
>>>> -struct ilist_traits;
>>>> -
>>>> -/// ilist_sentinel_traits - A fragment for template traits for intrusive list
>>>> -/// that provides default sentinel implementations for common operations.
>>>> -///
>>>> -/// ilist_sentinel_traits implements a lazy dynamic sentinel allocation
>>>> -/// strategy. The sentinel is stored in the prev field of ilist's Head.
>>>> -///
>>>> -template<typename NodeTy>
>>>> -struct ilist_sentinel_traits {
>>>> - /// createSentinel - create the dynamic sentinel
>>>> - static NodeTy *createSentinel() { return new NodeTy(); }
>>>> -
>>>> - /// destroySentinel - deallocate the dynamic sentinel
>>>> - static void destroySentinel(NodeTy *N) { delete N; }
>>>> -
>>>> - /// provideInitialHead - when constructing an ilist, provide a starting
>>>> - /// value for its Head
>>>> - /// @return null node to indicate that it needs to be allocated later
>>>> - static NodeTy *provideInitialHead() { return nullptr; }
>>>> -
>>>> - /// ensureHead - make sure that Head is either already
>>>> - /// initialized or assigned a fresh sentinel
>>>> - /// @return the sentinel
>>>> - static NodeTy *ensureHead(NodeTy *&Head) {
>>>> - if (!Head) {
>>>> - Head = ilist_traits<NodeTy>::createSentinel();
>>>> - ilist_traits<NodeTy>::noteHead(Head, Head);
>>>> - ilist_node_access::setNext(Head, nullptr);
>>>> - return Head;
>>>> - }
>>>> - return ilist_node_access::getPrev(Head);
>>>> - }
>>>> -
>>>> - /// noteHead - stash the sentinel into its default location
>>>> - static void noteHead(NodeTy *NewHead, NodeTy *Sentinel) {
>>>> - ilist_node_access::setPrev(NewHead, Sentinel);
>>>> - }
>>>> -};
>>>> -
>>>> -template <typename NodeTy> class ilist_half_node;
>>>> -template <typename NodeTy> class ilist_node;
>>>> +/// Type trait to check for a traits class that has a createSentinel member (as
>>>> +/// a canary for any of the ilist_sentinel_traits API).
>>>> +template <class TraitsT> struct HasCreateSentinel {
>>>> + typedef char Yes[1];
>>>> + typedef char No[2];
>>>> + template <size_t N> struct SFINAE {};
>>>>
>>>> -/// Traits with an embedded ilist_node as a sentinel.
>>>> -template <typename NodeTy> struct ilist_embedded_sentinel_traits {
>>>> - /// Get hold of the node that marks the end of the list.
>>>> - ///
>>>> - /// FIXME: This downcast is UB. See llvm.org/PR26753.
>>>> - LLVM_NO_SANITIZE("object-size")
>>>> - NodeTy *createSentinel() const {
>>>> - // Since i(p)lists always publicly derive from their corresponding traits,
>>>> - // placing a data member in this class will augment the i(p)list. But since
>>>> - // the NodeTy is expected to be publicly derive from ilist_node<NodeTy>,
>>>> - // there is a legal viable downcast from it to NodeTy. We use this trick to
>>>> - // superimpose an i(p)list with a "ghostly" NodeTy, which becomes the
>>>> - // sentinel. Dereferencing the sentinel is forbidden (save the
>>>> - // ilist_node<NodeTy>), so no one will ever notice the superposition.
>>>> - return static_cast<NodeTy *>(&Sentinel);
>>>> - }
>>>> - static void destroySentinel(NodeTy *) {}
>>>> -
>>>> - NodeTy *provideInitialHead() const { return createSentinel(); }
>>>> - NodeTy *ensureHead(NodeTy *) const { return createSentinel(); }
>>>> - static void noteHead(NodeTy *, NodeTy *) {}
>>>> + template <class U>
>>>> + static Yes &
>>>> + hasCreateSentinel(SFINAE<sizeof(make<U>().createSentinel())> * = 0);
>>>> + template <class U> static No &hasCreateSentinel(...);
>>>>
>>>> -private:
>>>> - mutable ilist_node<NodeTy> Sentinel;
>>>> + static const bool value =
>>>> + sizeof(hasCreateSentinel<TraitsT>(nullptr)) == sizeof(Yes);
>>>> };
>>>>
>>>> -/// Trait with an embedded ilist_half_node as a sentinel.
>>>> -template <typename NodeTy> struct ilist_half_embedded_sentinel_traits {
>>>> - /// Get hold of the node that marks the end of the list.
>>>> - ///
>>>> - /// FIXME: This downcast is UB. See llvm.org/PR26753.
>>>> - LLVM_NO_SANITIZE("object-size")
>>>> - NodeTy *createSentinel() const {
>>>> - // See comment in ilist_embedded_sentinel_traits::createSentinel().
>>>> - return static_cast<NodeTy *>(&Sentinel);
>>>> - }
>>>> - static void destroySentinel(NodeTy *) {}
>>>> -
>>>> - NodeTy *provideInitialHead() const { return createSentinel(); }
>>>> - NodeTy *ensureHead(NodeTy *) const { return createSentinel(); }
>>>> - static void noteHead(NodeTy *, NodeTy *) {}
>>>> -
>>>> -private:
>>>> - mutable ilist_half_node<NodeTy> Sentinel;
>>>> -};
>>>> +} // end namespace ilist_detail
>>>>
>>>> -/// Traits with an embedded full node as a sentinel.
>>>> -template <typename NodeTy> struct ilist_full_embedded_sentinel_traits {
>>>> - /// Get hold of the node that marks the end of the list.
>>>> - NodeTy *createSentinel() const { return &Sentinel; }
>>>> - static void destroySentinel(NodeTy *) {}
>>>> -
>>>> - NodeTy *provideInitialHead() const { return createSentinel(); }
>>>> - NodeTy *ensureHead(NodeTy *) const { return createSentinel(); }
>>>> - static void noteHead(NodeTy *, NodeTy *) {}
>>>> +template <typename NodeTy> struct ilist_traits;
>>>>
>>>> -private:
>>>> - mutable NodeTy Sentinel;
>>>> -};
>>>> +// TODO: Delete uses from subprojects, then delete these.
>>>> +template <typename NodeTy> struct ilist_sentinel_traits {};
>>>> +template <typename NodeTy> struct ilist_embedded_sentinel_traits {};
>>>> +template <typename NodeTy> struct ilist_half_embedded_sentinel_traits {};
>>>> +template <typename NodeTy> struct ilist_full_embedded_sentinel_traits {};
>>>>
>>>> /// ilist_node_traits - A fragment for template traits for intrusive list
>>>> /// that provides default node related operations.
>>>> @@ -219,8 +143,7 @@ struct ilist_node_traits {
>>>> /// for all common operations.
>>>> ///
>>>> template <typename NodeTy>
>>>> -struct ilist_default_traits : public ilist_sentinel_traits<NodeTy>,
>>>> - public ilist_node_traits<NodeTy> {};
>>>> +struct ilist_default_traits : public ilist_node_traits<NodeTy> {};
>>>>
>>>> // Template traits for intrusive list. By specializing this template class, you
>>>> // can change what next/prev fields are used to store the links...
>>>> @@ -263,16 +186,15 @@ public:
>>>> typedef node_type &node_reference;
>>>>
>>>> private:
>>>> - pointer NodePtr;
>>>> + node_pointer NodePtr = nullptr;
>>>>
>>>> public:
>>>> /// Create from an ilist_node.
>>>> - explicit ilist_iterator(node_reference N)
>>>> - : NodePtr(static_cast<NodeTy *>(&N)) {}
>>>> + explicit ilist_iterator(node_reference N) : NodePtr(&N) {}
>>>>
>>>> explicit ilist_iterator(pointer NP) : NodePtr(NP) {}
>>>> explicit ilist_iterator(reference NR) : NodePtr(&NR) {}
>>>> - ilist_iterator() : NodePtr(nullptr) {}
>>>> + ilist_iterator() = default;
>>>>
>>>> // This is templated so that we can allow constructing a const iterator from
>>>> // a nonconst iterator...
>>>> @@ -281,20 +203,23 @@ public:
>>>> const ilist_iterator<node_ty> &RHS,
>>>> typename std::enable_if<std::is_convertible<node_ty *, NodeTy *>::value,
>>>> void *>::type = nullptr)
>>>> - : NodePtr(RHS.getNodePtrUnchecked()) {}
>>>> + : NodePtr(RHS.getNodePtr()) {}
>>>>
>>>> // This is templated so that we can allow assigning to a const iterator from
>>>> // a nonconst iterator...
>>>> template <class node_ty>
>>>> const ilist_iterator &operator=(const ilist_iterator<node_ty> &RHS) {
>>>> - NodePtr = RHS.getNodePtrUnchecked();
>>>> + NodePtr = RHS.getNodePtr();
>>>> return *this;
>>>> }
>>>>
>>>> void reset(pointer NP) { NodePtr = NP; }
>>>>
>>>> // Accessors...
>>>> - reference operator*() const { return *NodePtr; }
>>>> + reference operator*() const {
>>>> + assert(!NodePtr->isKnownSentinel());
>>>> + return static_cast<NodeTy &>(*getNodePtr());
>>>> + }
>>>> pointer operator->() const { return &operator*(); }
>>>>
>>>> // Comparison operators
>>>> @@ -328,9 +253,6 @@ public:
>>>>
>>>> /// Get the underlying ilist_node.
>>>> node_pointer getNodePtr() const { return static_cast<node_pointer>(NodePtr); }
>>>> -
>>>> - // Internal interface, do not use...
>>>> - pointer getNodePtrUnchecked() const { return NodePtr; }
>>>> };
>>>>
>>>> // Allow ilist_iterators to convert into pointers to a node automatically when
>>>> @@ -356,56 +278,33 @@ template<typename NodeTy> struct simplif
>>>>
>>>> //===----------------------------------------------------------------------===//
>>>> //
>>>> -/// iplist - The subset of list functionality that can safely be used on nodes
>>>> -/// of polymorphic types, i.e. a heterogeneous list with a common base class that
>>>> -/// holds the next/prev pointers. The only state of the list itself is a single
>>>> -/// pointer to the head of the list.
>>>> -///
>>>> -/// This list can be in one of three interesting states:
>>>> -/// 1. The list may be completely unconstructed. In this case, the head
>>>> -/// pointer is null. When in this form, any query for an iterator (e.g.
>>>> -/// begin() or end()) causes the list to transparently change to state #2.
>>>> -/// 2. The list may be empty, but contain a sentinel for the end iterator. This
>>>> -/// sentinel is created by the Traits::createSentinel method and is a link
>>>> -/// in the list. When the list is empty, the pointer in the iplist points
>>>> -/// to the sentinel. Once the sentinel is constructed, it
>>>> -/// is not destroyed until the list is.
>>>> -/// 3. The list may contain actual objects in it, which are stored as a doubly
>>>> -/// linked list of nodes. One invariant of the list is that the predecessor
>>>> -/// of the first node in the list always points to the last node in the list,
>>>> -/// and the successor pointer for the sentinel (which always stays at the
>>>> -/// end of the list) is always null.
>>>> -///
>>>> +/// The subset of list functionality that can safely be used on nodes of
>>>> +/// polymorphic types, i.e. a heterogeneous list with a common base class that
>>>> +/// holds the next/prev pointers. The only state of the list itself is an
>>>> +/// ilist_sentinel, which holds pointers to the first and last nodes in the
>>>> +/// list.
>>>> template <typename NodeTy, typename Traits = ilist_traits<NodeTy>>
>>>> class iplist : public Traits, ilist_node_access {
>>>> + // TODO: Drop these assertions anytime after 4.0 is branched (keep them for
>>>> + // one release to help out-of-tree code update).
>>>> #if !defined(_MSC_VER)
>>>> // FIXME: This fails in MSVC, but it's worth keeping around to help
>>>> // non-Windows users root out bugs in their ilist_traits.
>>>> static_assert(!ilist_detail::HasGetNext<Traits, NodeTy>::value,
>>>> "ilist next and prev links are not customizable!");
>>>> + static_assert(!ilist_detail::HasCreateSentinel<Traits>::value,
>>>> + "ilist sentinel is not customizable!");
>>>> #endif
>>>>
>>>> - mutable NodeTy *Head;
>>>> + ilist_sentinel<NodeTy> Sentinel;
>>>>
>>>> - // Use the prev node pointer of 'head' as the tail pointer. This is really a
>>>> - // circularly linked list where we snip the 'next' link from the sentinel node
>>>> - // back to the first node in the list (to preserve assertions about going off
>>>> - // the end of the list).
>>>> - NodeTy *getTail() { return this->ensureHead(Head); }
>>>> - const NodeTy *getTail() const { return this->ensureHead(Head); }
>>>> - void setTail(NodeTy *N) const { this->noteHead(Head, N); }
>>>> -
>>>> - /// CreateLazySentinel - This method verifies whether the sentinel for the
>>>> - /// list has been created and lazily makes it if not.
>>>> - void CreateLazySentinel() const {
>>>> - this->ensureHead(Head);
>>>> - }
>>>> + typedef ilist_node<NodeTy> node_type;
>>>> + typedef const ilist_node<NodeTy> const_node_type;
>>>>
>>>> static bool op_less(NodeTy &L, NodeTy &R) { return L < R; }
>>>> static bool op_equal(NodeTy &L, NodeTy &R) { return L == R; }
>>>>
>>>> - // No fundamental reason why iplist can't be copyable, but the default
>>>> - // copy/copy-assign won't do.
>>>> + // Copying intrusively linked nodes doesn't make sense.
>>>> iplist(const iplist &) = delete;
>>>> void operator=(const iplist &) = delete;
>>>>
>>>> @@ -422,30 +321,14 @@ public:
>>>> typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
>>>> typedef std::reverse_iterator<iterator> reverse_iterator;
>>>>
>>>> - iplist() : Head(this->provideInitialHead()) {}
>>>> - ~iplist() {
>>>> - if (!Head) return;
>>>> - clear();
>>>> - Traits::destroySentinel(getTail());
>>>> - }
>>>> + iplist() = default;
>>>> + ~iplist() { clear(); }
>>>>
>>>> // Iterator creation methods.
>>>> - iterator begin() {
>>>> - CreateLazySentinel();
>>>> - return iterator(Head);
>>>> - }
>>>> - const_iterator begin() const {
>>>> - CreateLazySentinel();
>>>> - return const_iterator(Head);
>>>> - }
>>>> - iterator end() {
>>>> - CreateLazySentinel();
>>>> - return iterator(getTail());
>>>> - }
>>>> - const_iterator end() const {
>>>> - CreateLazySentinel();
>>>> - return const_iterator(getTail());
>>>> - }
>>>> + iterator begin() { return ++iterator(Sentinel); }
>>>> + const_iterator begin() const { return ++const_iterator(Sentinel); }
>>>> + iterator end() { return iterator(Sentinel); }
>>>> + const_iterator end() const { return const_iterator(Sentinel); }
>>>>
>>>> // reverse iterator creation methods.
>>>> reverse_iterator rbegin() { return reverse_iterator(end()); }
>>>> @@ -456,44 +339,39 @@ public:
>>>>
>>>> // Miscellaneous inspection routines.
>>>> size_type max_size() const { return size_type(-1); }
>>>> - bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const {
>>>> - return !Head || Head == getTail();
>>>> - }
>>>> + bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const { return Sentinel.empty(); }
>>>>
>>>> // Front and back accessor functions...
>>>> reference front() {
>>>> assert(!empty() && "Called front() on empty list!");
>>>> - return *Head;
>>>> + return *begin();
>>>> }
>>>> const_reference front() const {
>>>> assert(!empty() && "Called front() on empty list!");
>>>> - return *Head;
>>>> + return *begin();
>>>> }
>>>> reference back() {
>>>> assert(!empty() && "Called back() on empty list!");
>>>> - return *this->getPrev(getTail());
>>>> + return *--end();
>>>> }
>>>> const_reference back() const {
>>>> assert(!empty() && "Called back() on empty list!");
>>>> - return *this->getPrev(getTail());
>>>> + return *--end();
>>>> }
>>>>
>>>> void swap(iplist &RHS) {
>>>> assert(0 && "Swap does not use list traits callback correctly yet!");
>>>> - std::swap(Head, RHS.Head);
>>>> + std::swap(Sentinel, RHS.Sentinel);
>>>> }
>>>>
>>>> iterator insert(iterator where, NodeTy *New) {
>>>> - NodeTy *CurNode = where.getNodePtrUnchecked();
>>>> - NodeTy *PrevNode = this->getPrev(CurNode);
>>>> - this->setNext(New, CurNode);
>>>> - this->setPrev(New, PrevNode);
>>>> -
>>>> - if (CurNode != Head) // Is PrevNode off the beginning of the list?
>>>> - this->setNext(PrevNode, New);
>>>> - else
>>>> - Head = New;
>>>> - this->setPrev(CurNode, New);
>>>> + node_type *NewN = this->getNodePtr(New);
>>>> + node_type *Next = where.getNodePtr();
>>>> + node_type *Prev = this->getPrev(Next);
>>>> + this->setNext(NewN, Next);
>>>> + this->setPrev(NewN, Prev);
>>>> + this->setNext(Prev, NewN);
>>>> + this->setPrev(Next, NewN);
>>>>
>>>> this->addNodeToList(New); // Notify traits that we added a node...
>>>> return iterator(New);
>>>> @@ -513,24 +391,23 @@ public:
>>>> NodeTy *remove(iterator &IT) {
>>>> assert(IT != end() && "Cannot remove end of list!");
>>>> NodeTy *Node = &*IT;
>>>> - NodeTy *NextNode = this->getNext(Node);
>>>> - NodeTy *PrevNode = this->getPrev(Node);
>>>> -
>>>> - if (Node != Head) // Is PrevNode off the beginning of the list?
>>>> - this->setNext(PrevNode, NextNode);
>>>> - else
>>>> - Head = NextNode;
>>>> - this->setPrev(NextNode, PrevNode);
>>>> - IT.reset(NextNode);
>>>> + node_type *Base = this->getNodePtr(Node);
>>>> + node_type *Next = this->getNext(Base);
>>>> + node_type *Prev = this->getPrev(Base);
>>>> +
>>>> + this->setNext(Prev, Next);
>>>> + this->setPrev(Next, Prev);
>>>> + IT = iterator(*Next);
>>>> this->removeNodeFromList(Node); // Notify traits that we removed a node...
>>>>
>>>> // Set the next/prev pointers of the current node to null. This isn't
>>>> // strictly required, but this catches errors where a node is removed from
>>>> // an ilist (and potentially deleted) with iterators still pointing at it.
>>>> - // When those iterators are incremented or decremented, they will assert on
>>>> - // the null next/prev pointer instead of "usually working".
>>>> - this->setNext(Node, nullptr);
>>>> - this->setPrev(Node, nullptr);
>>>> + // After those iterators are incremented or decremented, they become
>>>> + // default-constructed iterators, and will assert on increment, decrement,
>>>> + // and dereference instead of "usually working".
>>>> + this->setNext(Base, nullptr);
>>>> + this->setPrev(Base, nullptr);
>>>> return Node;
>>>> }
>>>>
>>>> @@ -556,12 +433,7 @@ public:
>>>> ///
>>>> /// This should only be used immediately before freeing nodes in bulk to
>>>> /// avoid traversing the list and bringing all the nodes into cache.
>>>> - void clearAndLeakNodesUnsafely() {
>>>> - if (Head) {
>>>> - Head = getTail();
>>>> - this->setPrev(Head, Head);
>>>> - }
>>>> - }
>>>> + void clearAndLeakNodesUnsafely() { Sentinel.reset(); }
>>>>
>>>> private:
>>>> // transfer - The heart of the splice function. Move linked list nodes from
>>>> @@ -570,48 +442,34 @@ private:
>>>> void transfer(iterator position, iplist &L2, iterator first, iterator last) {
>>>> assert(first != last && "Should be checked by callers");
>>>> // Position cannot be contained in the range to be transferred.
>>>> - // Check for the most common mistake.
>>>> assert(position != first &&
>>>> + // Check for the most common mistake.
>>>> "Insertion point can't be one of the transferred nodes");
>>>>
>>>> - if (position != last) {
>>>> - // Note: we have to be careful about the case when we move the first node
>>>> - // in the list. This node is the list sentinel node and we can't move it.
>>>> - NodeTy *ThisSentinel = getTail();
>>>> - setTail(nullptr);
>>>> - NodeTy *L2Sentinel = L2.getTail();
>>>> - L2.setTail(nullptr);
>>>> -
>>>> - // Remove [first, last) from its old position.
>>>> - NodeTy *First = &*first, *Prev = this->getPrev(First);
>>>> - NodeTy *Next = last.getNodePtrUnchecked(), *Last = this->getPrev(Next);
>>>> - if (Prev)
>>>> - this->setNext(Prev, Next);
>>>> - else
>>>> - L2.Head = Next;
>>>> - this->setPrev(Next, Prev);
>>>> -
>>>> - // Splice [first, last) into its new position.
>>>> - NodeTy *PosNext = position.getNodePtrUnchecked();
>>>> - NodeTy *PosPrev = this->getPrev(PosNext);
>>>> -
>>>> - // Fix head of list...
>>>> - if (PosPrev)
>>>> - this->setNext(PosPrev, First);
>>>> - else
>>>> - Head = First;
>>>> - this->setPrev(First, PosPrev);
>>>> -
>>>> - // Fix end of list...
>>>> - this->setNext(Last, PosNext);
>>>> - this->setPrev(PosNext, Last);
>>>> -
>>>> - this->transferNodesFromList(L2, iterator(First), iterator(PosNext));
>>>> -
>>>> - // Now that everything is set, restore the pointers to the list sentinels.
>>>> - L2.setTail(L2Sentinel);
>>>> - setTail(ThisSentinel);
>>>> - }
>>>> + if (position == last)
>>>> + return;
>>>> +
>>>> + // Get raw hooks to the first and final nodes being transferred.
>>>> + node_type *First = first.getNodePtr();
>>>> + node_type *Final = (--last).getNodePtr();
>>>> +
>>>> + // Detach from old list/position.
>>>> + node_type *Prev = this->getPrev(First);
>>>> + node_type *Next = this->getNext(Final);
>>>> + this->setNext(Prev, Next);
>>>> + this->setPrev(Next, Prev);
>>>> +
>>>> + // Splice [First, Final] into its new list/position.
>>>> + Next = position.getNodePtr();
>>>> + Prev = this->getPrev(Next);
>>>> + this->setNext(Final, Next);
>>>> + this->setPrev(First, Prev);
>>>> + this->setNext(Prev, First);
>>>> + this->setPrev(Next, Final);
>>>> +
>>>> + // Callback. Note that the nodes have moved from before-last to
>>>> + // before-position.
>>>> + this->transferNodesFromList(L2, first, position);
>>>> }
>>>>
>>>> public:
>>>> @@ -621,7 +479,6 @@ public:
>>>> //
>>>>
>>>> size_type LLVM_ATTRIBUTE_UNUSED_RESULT size() const {
>>>> - if (!Head) return 0; // Don't require construction of sentinel if empty.
>>>> return std::distance(begin(), end());
>>>> }
>>>>
>>>> @@ -631,7 +488,7 @@ public:
>>>> return last;
>>>> }
>>>>
>>>> - void clear() { if (Head) erase(begin(), end()); }
>>>> + void clear() { erase(begin(), end()); }
>>>>
>>>> // Front and back inserters...
>>>> void push_front(NodeTy *val) { insert(begin(), val); }
>>>>
>>>> Modified: llvm/trunk/include/llvm/ADT/ilist_node.h
>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/ilist_node.h?rev=278974&r1=278973&r2=278974&view=diff
>>>> ==============================================================================
>>>> --- llvm/trunk/include/llvm/ADT/ilist_node.h (original)
>>>> +++ llvm/trunk/include/llvm/ADT/ilist_node.h Wed Aug 17 15:44:33 2016
>>>> @@ -15,6 +15,8 @@
>>>> #ifndef LLVM_ADT_ILIST_NODE_H
>>>> #define LLVM_ADT_ILIST_NODE_H
>>>>
>>>> +#include <llvm/ADT/PointerIntPair.h>
>>>> +
>>>> namespace llvm {
>>>>
>>>> template<typename NodeTy>
>>>> @@ -22,46 +24,81 @@ struct ilist_traits;
>>>> template <typename NodeTy> struct ilist_embedded_sentinel_traits;
>>>> template <typename NodeTy> struct ilist_half_embedded_sentinel_traits;
>>>>
>>>> -/// ilist_half_node - Base class that provides prev services for sentinels.
>>>> -///
>>>> -template<typename NodeTy>
>>>> -class ilist_half_node {
>>>> - friend struct ilist_traits<NodeTy>;
>>>> - friend struct ilist_half_embedded_sentinel_traits<NodeTy>;
>>>> - NodeTy *Prev;
>>>> -protected:
>>>> - NodeTy *getPrev() { return Prev; }
>>>> - const NodeTy *getPrev() const { return Prev; }
>>>> - void setPrev(NodeTy *P) { Prev = P; }
>>>> - ilist_half_node() : Prev(nullptr) {}
>>>> +/// Base class for ilist nodes.
>>>> +struct ilist_node_base {
>>>> +#ifdef LLVM_ENABLE_ABI_BREAKING_CHECKS
>>>> + PointerIntPair<ilist_node_base *, 1> PrevAndSentinel;
>>>> +
>>>> + void setPrev(ilist_node_base *Prev) { PrevAndSentinel.setPointer(Prev); }
>>>> + ilist_node_base *getPrev() const { return PrevAndSentinel.getPointer(); }
>>>> +
>>>> + bool isKnownSentinel() const { return PrevAndSentinel.getInt(); }
>>>> + void initializeSentinel() { PrevAndSentinel.setInt(true); }
>>>> +#else
>>>> + ilist_node_base *Prev = nullptr;
>>>> +
>>>> + void setPrev(ilist_node_base *Prev) { this->Prev = Prev; }
>>>> + ilist_node_base *getPrev() const { return Prev; }
>>>> +
>>>> + bool isKnownSentinel() const { return false; }
>>>> + void initializeSentinel() {}
>>>> +#endif
>>>> +
>>>> + ilist_node_base *Next = nullptr;
>>>> };
>>>>
>>>> struct ilist_node_access;
>>>> template <typename NodeTy> class ilist_iterator;
>>>> +template <typename NodeTy> class ilist_sentinel;
>>>>
>>>> -/// Base class that provides next/prev services for ilist nodes.
>>>> -template<typename NodeTy>
>>>> -class ilist_node : private ilist_half_node<NodeTy> {
>>>> +/// Templated wrapper class.
>>>> +template <typename NodeTy> class ilist_node : ilist_node_base {
>>>> friend struct ilist_node_access;
>>>> friend struct ilist_traits<NodeTy>;
>>>> friend struct ilist_half_embedded_sentinel_traits<NodeTy>;
>>>> friend struct ilist_embedded_sentinel_traits<NodeTy>;
>>>> - NodeTy *Next;
>>>> - NodeTy *getNext() { return Next; }
>>>> - const NodeTy *getNext() const { return Next; }
>>>> - void setNext(NodeTy *N) { Next = N; }
>>>> + friend class ilist_iterator<NodeTy>;
>>>> + friend class ilist_sentinel<NodeTy>;
>>>> +
>>>> protected:
>>>> - ilist_node() : Next(nullptr) {}
>>>> + ilist_node() = default;
>>>>
>>>> -public:
>>>> - ilist_iterator<NodeTy> getIterator() {
>>>> - // FIXME: Stop downcasting to create the iterator (potential UB).
>>>> - return ilist_iterator<NodeTy>(static_cast<NodeTy *>(this));
>>>> +private:
>>>> + ilist_node *getPrev() {
>>>> + return static_cast<ilist_node *>(ilist_node_base::getPrev());
>>>> + }
>>>> + ilist_node *getNext() { return static_cast<ilist_node *>(Next); }
>>>> +
>>>> + const ilist_node *getPrev() const {
>>>> + return static_cast<ilist_node *>(ilist_node_base::getPrev());
>>>> }
>>>> + const ilist_node *getNext() const { return static_cast<ilist_node *>(Next); }
>>>> +
>>>> + void setPrev(ilist_node *N) { ilist_node_base::setPrev(N); }
>>>> + void setNext(ilist_node *N) { Next = N; }
>>>> +
>>>> +public:
>>>> + ilist_iterator<NodeTy> getIterator() { return ilist_iterator<NodeTy>(*this); }
>>>> ilist_iterator<const NodeTy> getIterator() const {
>>>> - // FIXME: Stop downcasting to create the iterator (potential UB).
>>>> - return ilist_iterator<const NodeTy>(static_cast<const NodeTy *>(this));
>>>> + return ilist_iterator<const NodeTy>(*this);
>>>> }
>>>> +
>>>> + using ilist_node_base::isKnownSentinel;
>>>> +};
>>>> +
>>>> +template <typename NodeTy> class ilist_sentinel : public ilist_node<NodeTy> {
>>>> +public:
>>>> + ilist_sentinel() {
>>>> + ilist_node_base::initializeSentinel();
>>>> + reset();
>>>> + }
>>>> +
>>>> + void reset() {
>>>> + this->setPrev(this);
>>>> + this->setNext(this);
>>>> + }
>>>> +
>>>> + bool empty() const { return this == this->getPrev(); }
>>>> };
>>>>
>>>> /// An ilist node that can access its parent list.
>>>>
>>>> Modified: llvm/trunk/unittests/ADT/ilistTest.cpp
>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/ADT/ilistTest.cpp?rev=278974&r1=278973&r2=278974&view=diff
>>>> ==============================================================================
>>>> --- llvm/trunk/unittests/ADT/ilistTest.cpp (original)
>>>> +++ llvm/trunk/unittests/ADT/ilistTest.cpp Wed Aug 17 15:44:33 2016
>>>> @@ -128,4 +128,66 @@ TEST(ilistTest, UnsafeClear) {
>>>> EXPECT_EQ(6, List.back().Value);
>>>> }
>>>>
>>>> +struct NodeWithCallback : ilist_node<NodeWithCallback> {
>>>> + int Value = 0;
>>>> + bool IsInList = false;
>>>> +
>>>> + NodeWithCallback() = default;
>>>> + NodeWithCallback(int Value) : Value(Value) {}
>>>> + NodeWithCallback(const NodeWithCallback &) = delete;
>>>> +};
>>>> +
>>>> +} // end namespace
>>>> +
>>>> +namespace llvm {
>>>> +template <>
>>>> +struct ilist_traits<NodeWithCallback>
>>>> + : public ilist_node_traits<NodeWithCallback> {
>>>> + void addNodeToList(NodeWithCallback *N) { N->IsInList = true; }
>>>> + void removeNodeFromList(NodeWithCallback *N) { N->IsInList = false; }
>>>> +};
>>>> +} // end namespace llvm
>>>> +
>>>> +namespace {
>>>> +
>>>> +TEST(ilistTest, addNodeToList) {
>>>> + ilist<NodeWithCallback> L;
>>>> + NodeWithCallback N(7);
>>>> + ASSERT_FALSE(N.IsInList);
>>>> +
>>>> + L.insert(L.begin(), &N);
>>>> + ASSERT_EQ(1u, L.size());
>>>> + ASSERT_EQ(&N, &*L.begin());
>>>> + ASSERT_TRUE(N.IsInList);
>>>> +
>>>> + L.remove(&N);
>>>> + ASSERT_EQ(0u, L.size());
>>>> + ASSERT_FALSE(N.IsInList);
>>>> }
>>>> +
>>>> +struct PrivateNode : private ilist_node<PrivateNode> {
>>>> + friend struct llvm::ilist_node_access;
>>>> +
>>>> + int Value = 0;
>>>> +
>>>> + PrivateNode() = default;
>>>> + PrivateNode(int Value) : Value(Value) {}
>>>> + PrivateNode(const PrivateNode &) = delete;
>>>> +};
>>>> +
>>>> +TEST(ilistTest, privateNode) {
>>>> + // Instantiate various APIs to be sure they're callable when ilist_node is
>>>> + // inherited privately.
>>>> + ilist<NodeWithCallback> L;
>>>> + NodeWithCallback N(7);
>>>> + L.insert(L.begin(), &N);
>>>> + ++L.begin();
>>>> + (void)*L.begin();
>>>> + (void)(L.begin() == L.end());
>>>> +
>>>> + ilist<NodeWithCallback> L2;
>>>> + L2.splice(L2.end(), L);
>>>> + L2.remove(&N);
>>>> +}
>>>> +
>>>> +} // end namespace
>>>>
>>>>
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