/root/bitcoin/src/policy/truc_policy.cpp

Source (jump to first uncovered line)
// Copyright (c) 2022 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <policy/truc_policy.h>

#include <coins.h>
#include <consensus/amount.h>
#include <logging.h>
#include <tinyformat.h>
#include <util/check.h>

#include <algorithm>
#include <numeric>
#include <vector>

/** Helper for PackageTRUCChecks: Returns a vector containing the indices of transactions (within
 * package) that are direct parents of ptx. */
std::vector<size_t> FindInPackageParents(const Package& package, const CTransactionRef& ptx)
{
    std::vector<size_t> in_package_parents;

    std::set<Txid> possible_parents;
    for (auto &input : ptx->vin) {
        possible_parents.insert(input.prevout.hash);
    }

    for (size_t i{0}; i < package.size(); ++i) {
        const auto& tx = package.at(i);
        // We assume the package is sorted, so that we don't need to continue
        // looking past the transaction itself.
        if (&(*tx) == &(*ptx)) break;
        if (possible_parents.count(tx->GetHash())) {
            in_package_parents.push_back(i);
        }
    }
    return in_package_parents;
}

/** Helper for PackageTRUCChecks, storing info for a mempool or package parent. */
struct ParentInfo {
    /** Txid used to identify this parent by prevout */
    const Txid& m_txid;
    /** Wtxid used for debug string */
    const Wtxid& m_wtxid;
    /** version used to check inheritance of TRUC and non-TRUC */
    decltype(CTransaction::version) m_version;
    /** If parent is in mempool, whether it has any descendants in mempool. */
    bool m_has_mempool_descendant;

    ParentInfo() = delete;
    ParentInfo(const Txid& txid, const Wtxid& wtxid, decltype(CTransaction::version) version, bool has_mempool_descendant) :
        m_txid{txid}, m_wtxid{wtxid}, m_version{version},
        m_has_mempool_descendant{has_mempool_descendant}
    {}
};

std::optional<std::string> PackageTRUCChecks(const CTransactionRef& ptx, int64_t vsize,
                                           const Package& package,
                                           const CTxMemPool::setEntries& mempool_ancestors)
{
    // This function is specialized for these limits, and must be reimplemented if they ever change.
    static_assert(TRUC_ANCESTOR_LIMIT == 2);
    static_assert(TRUC_DESCENDANT_LIMIT == 2);

    const auto in_package_parents{FindInPackageParents(package, ptx)};

    // Now we have all ancestors, so we can start checking TRUC rules.
    if (ptx->version == TRUC_VERSION) {
        // SingleTRUCChecks should have checked this already.
        if (!Assume(vsize <= TRUC_MAX_VSIZE)) {
            return strprintf("version=3 tx %s (wtxid=%s) is too big: %u > %u virtual bytes",
                             ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(), vsize, TRUC_MAX_VSIZE);
        }

        if (mempool_ancestors.size() + in_package_parents.size() + 1 > TRUC_ANCESTOR_LIMIT) {
            return strprintf("tx %s (wtxid=%s) would have too many ancestors",
                             ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString());
        }

        const bool has_parent{mempool_ancestors.size() + in_package_parents.size() > 0};
        if (has_parent) {
            // A TRUC child cannot be too large.
            if (vsize > TRUC_CHILD_MAX_VSIZE) {
                return strprintf("version=3 child tx %s (wtxid=%s) is too big: %u > %u virtual bytes",
                                 ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(),
                                 vsize, TRUC_CHILD_MAX_VSIZE);
            }

            // Exactly 1 parent exists, either in mempool or package. Find it.
            const auto parent_info = [&] {
                if (mempool_ancestors.size() > 0) {
                    auto& mempool_parent = *mempool_ancestors.begin();
                    return ParentInfo{mempool_parent->GetTx().GetHash(),
                                      mempool_parent->GetTx().GetWitnessHash(),
                                      mempool_parent->GetTx().version,
                                      /*has_mempool_descendant=*/mempool_parent->GetCountWithDescendants() > 1};
                } else {
                    auto& parent_index = in_package_parents.front();
                    auto& package_parent = package.at(parent_index);
                    return ParentInfo{package_parent->GetHash(),
                                      package_parent->GetWitnessHash(),
                                      package_parent->version,
                                      /*has_mempool_descendant=*/false};
                }
            }();

            // If there is a parent, it must have the right version.
            if (parent_info.m_version != TRUC_VERSION) {
                return strprintf("version=3 tx %s (wtxid=%s) cannot spend from non-version=3 tx %s (wtxid=%s)",
                                 ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(),
                                 parent_info.m_txid.ToString(), parent_info.m_wtxid.ToString());
            }

            for (const auto& package_tx : package) {
                // Skip same tx.
                if (&(*package_tx) == &(*ptx)) continue;

                for (auto& input : package_tx->vin) {
                    // Fail if we find another tx with the same parent. We don't check whether the
                    // sibling is to-be-replaced (done in SingleTRUCChecks) because these transactions
                    // are within the same package.
                    if (input.prevout.hash == parent_info.m_txid) {
                        return strprintf("tx %s (wtxid=%s) would exceed descendant count limit",
                                         parent_info.m_txid.ToString(),
                                         parent_info.m_wtxid.ToString());
                    }

                    // This tx can't have both a parent and an in-package child.
                    if (input.prevout.hash == ptx->GetHash()) {
                        return strprintf("tx %s (wtxid=%s) would have too many ancestors",
                                         package_tx->GetHash().ToString(), package_tx->GetWitnessHash().ToString());
                    }
                }
            }

            if (parent_info.m_has_mempool_descendant) {
                return strprintf("tx %s (wtxid=%s) would exceed descendant count limit",
                                parent_info.m_txid.ToString(), parent_info.m_wtxid.ToString());
            }
        }
    } else {
        // Non-TRUC transactions cannot have TRUC parents.
        for (auto it : mempool_ancestors) {
            if (it->GetTx().version == TRUC_VERSION) {
                return strprintf("non-version=3 tx %s (wtxid=%s) cannot spend from version=3 tx %s (wtxid=%s)",
                                 ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(),
                                 it->GetSharedTx()->GetHash().ToString(), it->GetSharedTx()->GetWitnessHash().ToString());
            }
        }
        for (const auto& index: in_package_parents) {
            if (package.at(index)->version == TRUC_VERSION) {
                return strprintf("non-version=3 tx %s (wtxid=%s) cannot spend from version=3 tx %s (wtxid=%s)",
                                 ptx->GetHash().ToString(),
                                 ptx->GetWitnessHash().ToString(),
                                 package.at(index)->GetHash().ToString(),
                                 package.at(index)->GetWitnessHash().ToString());
            }
        }
    }
    return std::nullopt;
}

std::optional<std::pair<std::string, CTransactionRef>> SingleTRUCChecks(const CTransactionRef& ptx,
                                          const CTxMemPool::setEntries& mempool_ancestors,
                                          const std::set<Txid>& direct_conflicts,
                                          int64_t vsize)
{
    // Check TRUC and non-TRUC inheritance.
    for (const auto& entry : mempool_ancestors) {
        if (ptx->version != TRUC_VERSION && entry->GetTx().version == TRUC_VERSION) {
            return std::make_pair(strprintf("non-version=3 tx %s (wtxid=%s) cannot spend from version=3 tx %s (wtxid=%s)",
                             ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(),
                             entry->GetSharedTx()->GetHash().ToString(), entry->GetSharedTx()->GetWitnessHash().ToString()),
                nullptr);
        } else if (ptx->version == TRUC_VERSION && entry->GetTx().version != TRUC_VERSION) {
            return std::make_pair(strprintf("version=3 tx %s (wtxid=%s) cannot spend from non-version=3 tx %s (wtxid=%s)",
                             ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(),
                             entry->GetSharedTx()->GetHash().ToString(), entry->GetSharedTx()->GetWitnessHash().ToString()),
                nullptr);
        }
    }

    // This function is specialized for these limits, and must be reimplemented if they ever change.
    static_assert(TRUC_ANCESTOR_LIMIT == 2);
    static_assert(TRUC_DESCENDANT_LIMIT == 2);

    // The rest of the rules only apply to transactions with version=3.
    if (ptx->version != TRUC_VERSION) return std::nullopt;

    if (vsize > TRUC_MAX_VSIZE) {
        return std::make_pair(strprintf("version=3 tx %s (wtxid=%s) is too big: %u > %u virtual bytes",
                         ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(), vsize, TRUC_MAX_VSIZE),
            nullptr);
    }

    // Check that TRUC_ANCESTOR_LIMIT would not be violated.
    if (mempool_ancestors.size() + 1 > TRUC_ANCESTOR_LIMIT) {
        return std::make_pair(strprintf("tx %s (wtxid=%s) would have too many ancestors",
                         ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString()),
            nullptr);
    }

    // Remaining checks only pertain to transactions with unconfirmed ancestors.
    if (mempool_ancestors.size() > 0) {
        // If this transaction spends TRUC parents, it cannot be too large.
        if (vsize > TRUC_CHILD_MAX_VSIZE) {
            return std::make_pair(strprintf("version=3 child tx %s (wtxid=%s) is too big: %u > %u virtual bytes",
                             ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(), vsize, TRUC_CHILD_MAX_VSIZE),
                nullptr);
        }

        // Check the descendant counts of in-mempool ancestors.
        const auto& parent_entry = *mempool_ancestors.begin();
        // If there are any ancestors, this is the only child allowed. The parent cannot have any
        // other descendants. We handle the possibility of multiple children as that case is
        // possible through a reorg.
        const auto& children = parent_entry->GetMemPoolChildrenConst();
        // Don't double-count a transaction that is going to be replaced. This logic assumes that
        // any descendant of the TRUC transaction is a direct child, which makes sense because a
        // TRUC transaction can only have 1 descendant.
        const bool child_will_be_replaced = !children.empty() &&
            std::any_of(children.cbegin(), children.cend(),
                [&direct_conflicts](const CTxMemPoolEntry& child){return direct_conflicts.count(child.GetTx().GetHash()) > 0;});
        if (parent_entry->GetCountWithDescendants() + 1 > TRUC_DESCENDANT_LIMIT && !child_will_be_replaced) {
            // Allow sibling eviction for TRUC transaction: if another child already exists, even if
            // we don't conflict inputs with it, consider evicting it under RBF rules. We rely on TRUC rules
            // only permitting 1 descendant, as otherwise we would need to have logic for deciding
            // which descendant to evict. Skip if this isn't true, e.g. if the transaction has
            // multiple children or the sibling also has descendants due to a reorg.
            const bool consider_sibling_eviction{parent_entry->GetCountWithDescendants() == 2 &&
                children.begin()->get().GetCountWithAncestors() == 2};

            // Return the sibling if its eviction can be considered. Provide the "descendant count
            // limit" string either way, as the caller may decide not to do sibling eviction.
            return std::make_pair(strprintf("tx %u (wtxid=%s) would exceed descendant count limit",
                                            parent_entry->GetSharedTx()->GetHash().ToString(),
                                            parent_entry->GetSharedTx()->GetWitnessHash().ToString()),
                                  consider_sibling_eviction ?  children.begin()->get().GetSharedTx() : nullptr);
        }
    }
    return std::nullopt;
}

Coverage Report

Created: 2025-04-09 20:00

Line	Count	Source (jump to first uncovered line)
1		// Copyright (c) 2022 The Bitcoin Core developers
2		// Distributed under the MIT software license, see the accompanying
3		// file COPYING or http://www.opensource.org/licenses/mit-license.php.
4
5		#include <policy/truc_policy.h>
6
7		#include <coins.h>
8		#include <consensus/amount.h>
9		#include <logging.h>
10		#include <tinyformat.h>
11		#include <util/check.h>
12
13		#include <algorithm>
14		#include <numeric>
15		#include <vector>
16
17		/** Helper for PackageTRUCChecks: Returns a vector containing the indices of transactions (within
18		* package) that are direct parents of ptx. */
19		std::vector<size_t> FindInPackageParents(const Package& package, const CTransactionRef& ptx)
20	0	{
21	0	std::vector<size_t> in_package_parents;
22
23	0	std::set<Txid> possible_parents;
24	0	for (auto &input : ptx->vin) {
25	0	possible_parents.insert(input.prevout.hash);
26	0	}
27
28	0	for (size_t i{0}; i < package.size(); ++i) {
29	0	const auto& tx = package.at(i);
30		// We assume the package is sorted, so that we don't need to continue
31		// looking past the transaction itself.
32	0	if (&(tx) == &(ptx)) break;
33	0	if (possible_parents.count(tx->GetHash())) {
34	0	in_package_parents.push_back(i);
35	0	}
36	0	}
37	0	return in_package_parents;
38	0	}
39
40		/** Helper for PackageTRUCChecks, storing info for a mempool or package parent. */
41		struct ParentInfo {
42		/** Txid used to identify this parent by prevout */
43		const Txid& m_txid;
44		/** Wtxid used for debug string */
45		const Wtxid& m_wtxid;
46		/** version used to check inheritance of TRUC and non-TRUC */
47		decltype(CTransaction::version) m_version;
48		/** If parent is in mempool, whether it has any descendants in mempool. */
49		bool m_has_mempool_descendant;
50
51		ParentInfo() = delete;
52		ParentInfo(const Txid& txid, const Wtxid& wtxid, decltype(CTransaction::version) version, bool has_mempool_descendant) :
53	0	m_txid{txid}, m_wtxid{wtxid}, m_version{version},
54	0	m_has_mempool_descendant{has_mempool_descendant}
55	0	{}
56		};
57
58		std::optional<std::string> PackageTRUCChecks(const CTransactionRef& ptx, int64_t vsize,
59		const Package& package,
60		const CTxMemPool::setEntries& mempool_ancestors)
61	0	{
62		// This function is specialized for these limits, and must be reimplemented if they ever change.
63	0	static_assert(TRUC_ANCESTOR_LIMIT == 2);
64	0	static_assert(TRUC_DESCENDANT_LIMIT == 2);
65
66	0	const auto in_package_parents{FindInPackageParents(package, ptx)};
67
68		// Now we have all ancestors, so we can start checking TRUC rules.
69	0	if (ptx->version == TRUC_VERSION) {
70		// SingleTRUCChecks should have checked this already.
71	0	if (!Assume(vsize <= TRUC_MAX_VSIZE)) {
72	0	return strprintf("version=3 tx %s (wtxid=%s) is too big: %u > %u virtual bytes",
73	0	ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(), vsize, TRUC_MAX_VSIZE);
74	0	}
75
76	0	if (mempool_ancestors.size() + in_package_parents.size() + 1 > TRUC_ANCESTOR_LIMIT) {
77	0	return strprintf("tx %s (wtxid=%s) would have too many ancestors",
78	0	ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString());
79	0	}
80
81	0	const bool has_parent{mempool_ancestors.size() + in_package_parents.size() > 0};
82	0	if (has_parent) {
83		// A TRUC child cannot be too large.
84	0	if (vsize > TRUC_CHILD_MAX_VSIZE) {
85	0	return strprintf("version=3 child tx %s (wtxid=%s) is too big: %u > %u virtual bytes",
86	0	ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(),
87	0	vsize, TRUC_CHILD_MAX_VSIZE);
88	0	}
89
90		// Exactly 1 parent exists, either in mempool or package. Find it.
91	0	const auto parent_info = [&] {
92	0	if (mempool_ancestors.size() > 0) {
93	0	auto& mempool_parent = *mempool_ancestors.begin();
94	0	return ParentInfo{mempool_parent->GetTx().GetHash(),
95	0	mempool_parent->GetTx().GetWitnessHash(),
96	0	mempool_parent->GetTx().version,
97	0	/has_mempool_descendant=/mempool_parent->GetCountWithDescendants() > 1};
98	0	} else {
99	0	auto& parent_index = in_package_parents.front();
100	0	auto& package_parent = package.at(parent_index);
101	0	return ParentInfo{package_parent->GetHash(),
102	0	package_parent->GetWitnessHash(),
103	0	package_parent->version,
104	0	/has_mempool_descendant=/false};
105	0	}
106	0	}();
107
108		// If there is a parent, it must have the right version.
109	0	if (parent_info.m_version != TRUC_VERSION) {
110	0	return strprintf("version=3 tx %s (wtxid=%s) cannot spend from non-version=3 tx %s (wtxid=%s)",
111	0	ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(),
112	0	parent_info.m_txid.ToString(), parent_info.m_wtxid.ToString());
113	0	}
114
115	0	for (const auto& package_tx : package) {
116		// Skip same tx.
117	0	if (&(package_tx) == &(ptx)) continue;
118
119	0	for (auto& input : package_tx->vin) {
120		// Fail if we find another tx with the same parent. We don't check whether the
121		// sibling is to-be-replaced (done in SingleTRUCChecks) because these transactions
122		// are within the same package.
123	0	if (input.prevout.hash == parent_info.m_txid) {
124	0	return strprintf("tx %s (wtxid=%s) would exceed descendant count limit",
125	0	parent_info.m_txid.ToString(),
126	0	parent_info.m_wtxid.ToString());
127	0	}
128
129		// This tx can't have both a parent and an in-package child.
130	0	if (input.prevout.hash == ptx->GetHash()) {
131	0	return strprintf("tx %s (wtxid=%s) would have too many ancestors",
132	0	package_tx->GetHash().ToString(), package_tx->GetWitnessHash().ToString());
133	0	}
134	0	}
135	0	}
136
137	0	if (parent_info.m_has_mempool_descendant) {
138	0	return strprintf("tx %s (wtxid=%s) would exceed descendant count limit",
139	0	parent_info.m_txid.ToString(), parent_info.m_wtxid.ToString());
140	0	}
141	0	}
142	0	} else {
143		// Non-TRUC transactions cannot have TRUC parents.
144	0	for (auto it : mempool_ancestors) {
145	0	if (it->GetTx().version == TRUC_VERSION) {
146	0	return strprintf("non-version=3 tx %s (wtxid=%s) cannot spend from version=3 tx %s (wtxid=%s)",
147	0	ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(),
148	0	it->GetSharedTx()->GetHash().ToString(), it->GetSharedTx()->GetWitnessHash().ToString());
149	0	}
150	0	}
151	0	for (const auto& index: in_package_parents) {
152	0	if (package.at(index)->version == TRUC_VERSION) {
153	0	return strprintf("non-version=3 tx %s (wtxid=%s) cannot spend from version=3 tx %s (wtxid=%s)",
154	0	ptx->GetHash().ToString(),
155	0	ptx->GetWitnessHash().ToString(),
156	0	package.at(index)->GetHash().ToString(),
157	0	package.at(index)->GetWitnessHash().ToString());
158	0	}
159	0	}
160	0	}
161	0	return std::nullopt;
162	0	}
163
164		std::optional<std::pair<std::string, CTransactionRef>> SingleTRUCChecks(const CTransactionRef& ptx,
165		const CTxMemPool::setEntries& mempool_ancestors,
166		const std::set<Txid>& direct_conflicts,
167		int64_t vsize)
168	0	{
169		// Check TRUC and non-TRUC inheritance.
170	0	for (const auto& entry : mempool_ancestors) {
171	0	if (ptx->version != TRUC_VERSION && entry->GetTx().version == TRUC_VERSION) {
172	0	return std::make_pair(strprintf("non-version=3 tx %s (wtxid=%s) cannot spend from version=3 tx %s (wtxid=%s)",
173	0	ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(),
174	0	entry->GetSharedTx()->GetHash().ToString(), entry->GetSharedTx()->GetWitnessHash().ToString()),
175	0	nullptr);
176	0	} else if (ptx->version == TRUC_VERSION && entry->GetTx().version != TRUC_VERSION) {
177	0	return std::make_pair(strprintf("version=3 tx %s (wtxid=%s) cannot spend from non-version=3 tx %s (wtxid=%s)",
178	0	ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(),
179	0	entry->GetSharedTx()->GetHash().ToString(), entry->GetSharedTx()->GetWitnessHash().ToString()),
180	0	nullptr);
181	0	}
182	0	}
183
184		// This function is specialized for these limits, and must be reimplemented if they ever change.
185	0	static_assert(TRUC_ANCESTOR_LIMIT == 2);
186	0	static_assert(TRUC_DESCENDANT_LIMIT == 2);
187
188		// The rest of the rules only apply to transactions with version=3.
189	0	if (ptx->version != TRUC_VERSION) return std::nullopt;
190
191	0	if (vsize > TRUC_MAX_VSIZE) {
192	0	return std::make_pair(strprintf("version=3 tx %s (wtxid=%s) is too big: %u > %u virtual bytes",
193	0	ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(), vsize, TRUC_MAX_VSIZE),
194	0	nullptr);
195	0	}
196
197		// Check that TRUC_ANCESTOR_LIMIT would not be violated.
198	0	if (mempool_ancestors.size() + 1 > TRUC_ANCESTOR_LIMIT) {
199	0	return std::make_pair(strprintf("tx %s (wtxid=%s) would have too many ancestors",
200	0	ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString()),
201	0	nullptr);
202	0	}
203
204		// Remaining checks only pertain to transactions with unconfirmed ancestors.
205	0	if (mempool_ancestors.size() > 0) {
206		// If this transaction spends TRUC parents, it cannot be too large.
207	0	if (vsize > TRUC_CHILD_MAX_VSIZE) {
208	0	return std::make_pair(strprintf("version=3 child tx %s (wtxid=%s) is too big: %u > %u virtual bytes",
209	0	ptx->GetHash().ToString(), ptx->GetWitnessHash().ToString(), vsize, TRUC_CHILD_MAX_VSIZE),
210	0	nullptr);
211	0	}
212
213		// Check the descendant counts of in-mempool ancestors.
214	0	const auto& parent_entry = *mempool_ancestors.begin();
215		// If there are any ancestors, this is the only child allowed. The parent cannot have any
216		// other descendants. We handle the possibility of multiple children as that case is
217		// possible through a reorg.
218	0	const auto& children = parent_entry->GetMemPoolChildrenConst();
219		// Don't double-count a transaction that is going to be replaced. This logic assumes that
220		// any descendant of the TRUC transaction is a direct child, which makes sense because a
221		// TRUC transaction can only have 1 descendant.
222	0	const bool child_will_be_replaced = !children.empty() &&
223	0	std::any_of(children.cbegin(), children.cend(),
224	0	[&direct_conflicts](const CTxMemPoolEntry& child){return direct_conflicts.count(child.GetTx().GetHash()) > 0;});
225	0	if (parent_entry->GetCountWithDescendants() + 1 > TRUC_DESCENDANT_LIMIT && !child_will_be_replaced) {
226		// Allow sibling eviction for TRUC transaction: if another child already exists, even if
227		// we don't conflict inputs with it, consider evicting it under RBF rules. We rely on TRUC rules
228		// only permitting 1 descendant, as otherwise we would need to have logic for deciding
229		// which descendant to evict. Skip if this isn't true, e.g. if the transaction has
230		// multiple children or the sibling also has descendants due to a reorg.
231	0	const bool consider_sibling_eviction{parent_entry->GetCountWithDescendants() == 2 &&
232	0	children.begin()->get().GetCountWithAncestors() == 2};
233
234		// Return the sibling if its eviction can be considered. Provide the "descendant count
235		// limit" string either way, as the caller may decide not to do sibling eviction.
236	0	return std::make_pair(strprintf("tx %u (wtxid=%s) would exceed descendant count limit",
237	0	parent_entry->GetSharedTx()->GetHash().ToString(),
238	0	parent_entry->GetSharedTx()->GetWitnessHash().ToString()),
239	0	consider_sibling_eviction ? children.begin()->get().GetSharedTx() : nullptr);
240	0	}
241	0	}
242	0	return std::nullopt;
243	0	}