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[libc++] Add a few _LIBCPP_ASSERTs in __tree

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Several helper functions specify preconditions as comments, but we never
check them. I ran across a bug report (without a reproducer) in this code,
and I thought that having these assertions in place would make it easier
to troubleshoot.

Differential Revision: https://reviews.llvm.org/D124477
This commit is contained in:
Louis Dionne 2022-04-26 15:02:40 -06:00
parent b9f3b7f89a
commit 990ea3925b
1 changed files with 17 additions and 12 deletions
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29
libcxx/include/__tree
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@ -141,35 +141,35 @@ __tree_invariant(_NodePtr __root)
}
// Returns: pointer to the left-most node under __x.
// Precondition: __x != nullptr.
template <class _NodePtr>
inline _LIBCPP_INLINE_VISIBILITY
_NodePtr
__tree_min(_NodePtr __x) _NOEXCEPT
{
_LIBCPP_ASSERT(__x != nullptr, "Root node shouldn't be null");
while (__x->__left_ != nullptr)
__x = __x->__left_;
return __x;
}
// Returns: pointer to the right-most node under __x.
// Precondition: __x != nullptr.
template <class _NodePtr>
inline _LIBCPP_INLINE_VISIBILITY
_NodePtr
__tree_max(_NodePtr __x) _NOEXCEPT
{
_LIBCPP_ASSERT(__x != nullptr, "Root node shouldn't be null");
while (__x->__right_ != nullptr)
__x = __x->__right_;
return __x;
}
// Returns: pointer to the next in-order node after __x.
// Precondition: __x != nullptr.
template <class _NodePtr>
_NodePtr
__tree_next(_NodePtr __x) _NOEXCEPT
{
_LIBCPP_ASSERT(__x != nullptr, "node shouldn't be null");
if (__x->__right_ != nullptr)
return _VSTD::__tree_min(__x->__right_);
while (!_VSTD::__tree_is_left_child(__x))
@ -182,6 +182,7 @@ inline _LIBCPP_INLINE_VISIBILITY
_EndNodePtr
__tree_next_iter(_NodePtr __x) _NOEXCEPT
{
_LIBCPP_ASSERT(__x != nullptr, "node shouldn't be null");
if (__x->__right_ != nullptr)
return static_cast<_EndNodePtr>(_VSTD::__tree_min(__x->__right_));
while (!_VSTD::__tree_is_left_child(__x))
@ -190,13 +191,13 @@ __tree_next_iter(_NodePtr __x) _NOEXCEPT
}
// Returns: pointer to the previous in-order node before __x.
// Precondition: __x != nullptr.
// Note: __x may be the end node.
template <class _NodePtr, class _EndNodePtr>
inline _LIBCPP_INLINE_VISIBILITY
_NodePtr
__tree_prev_iter(_EndNodePtr __x) _NOEXCEPT
{
_LIBCPP_ASSERT(__x != nullptr, "node shouldn't be null");
if (__x->__left_ != nullptr)
return _VSTD::__tree_max(__x->__left_);
_NodePtr __xx = static_cast<_NodePtr>(__x);
@ -206,11 +207,11 @@ __tree_prev_iter(_EndNodePtr __x) _NOEXCEPT
}
// Returns: pointer to a node which has no children
// Precondition: __x != nullptr.
template <class _NodePtr>
_NodePtr
__tree_leaf(_NodePtr __x) _NOEXCEPT
{
_LIBCPP_ASSERT(__x != nullptr, "node shouldn't be null");
while (true)
{
if (__x->__left_ != nullptr)
@ -230,11 +231,12 @@ __tree_leaf(_NodePtr __x) _NOEXCEPT
// Effects: Makes __x->__right_ the subtree root with __x as its left child
// while preserving in-order order.
// Precondition: __x->__right_ != nullptr
template <class _NodePtr>
void
__tree_left_rotate(_NodePtr __x) _NOEXCEPT
{
_LIBCPP_ASSERT(__x != nullptr, "node shouldn't be null");
_LIBCPP_ASSERT(__x->__right_ != nullptr, "node should have a right child");
_NodePtr __y = __x->__right_;
__x->__right_ = __y->__left_;
if (__x->__right_ != nullptr)
@ -250,11 +252,12 @@ __tree_left_rotate(_NodePtr __x) _NOEXCEPT
// Effects: Makes __x->__left_ the subtree root with __x as its right child
// while preserving in-order order.
// Precondition: __x->__left_ != nullptr
template <class _NodePtr>
void
__tree_right_rotate(_NodePtr __x) _NOEXCEPT
{
_LIBCPP_ASSERT(__x != nullptr, "node shouldn't be null");
_LIBCPP_ASSERT(__x->__left_ != nullptr, "node should have a left child");
_NodePtr __y = __x->__left_;
__x->__left_ = __y->__right_;
if (__x->__left_ != nullptr)
@ -269,8 +272,7 @@ __tree_right_rotate(_NodePtr __x) _NOEXCEPT
}
// Effects: Rebalances __root after attaching __x to a leaf.
// Precondition: __root != nulptr && __x != nullptr.
// __x has no children.
// Precondition: __x has no children.
// __x == __root or == a direct or indirect child of __root.
// If __x were to be unlinked from __root (setting __root to
// nullptr if __root == __x), __tree_invariant(__root) == true.
@ -280,6 +282,8 @@ template <class _NodePtr>
void
__tree_balance_after_insert(_NodePtr __root, _NodePtr __x) _NOEXCEPT
{
_LIBCPP_ASSERT(__root != nullptr, "Root of the tree shouldn't be null");
_LIBCPP_ASSERT(__x != nullptr, "Can't attach null node to a leaf");
__x->__is_black_ = __x == __root;
while (__x != __root && !__x->__parent_unsafe()->__is_black_)
{
@ -339,9 +343,7 @@ __tree_balance_after_insert(_NodePtr __root, _NodePtr __x) _NOEXCEPT
}
}
// Precondition: __root != nullptr && __z != nullptr.
// __tree_invariant(__root) == true.
// __z == __root or == a direct or indirect child of __root.
// Precondition: __z == __root or == a direct or indirect child of __root.
// Effects: unlinks __z from the tree rooted at __root, rebalancing as needed.
// Postcondition: __tree_invariant(end_node->__left_) == true && end_node->__left_
// nor any of its children refer to __z. end_node->__left_
@ -350,6 +352,9 @@ template <class _NodePtr>
void
__tree_remove(_NodePtr __root, _NodePtr __z) _NOEXCEPT
{
_LIBCPP_ASSERT(__root != nullptr, "Root node should not be null");
_LIBCPP_ASSERT(__z != nullptr, "The node to remove should not be null");
_LIBCPP_DEBUG_ASSERT(__tree_invariant(__root), "The tree invariants should hold");
// __z will be removed from the tree. Client still needs to destruct/deallocate it
// __y is either __z, or if __z has two children, __tree_next(__z).
// __y will have at most one child.