From 28ba0313eac37e4a900b7e97af7169ce999c4024 Mon Sep 17 00:00:00 2001
From: Carl Dong <contact@carldong.me>
Date: Tue, 15 Mar 2022 19:19:58 -0400
Subject: [PATCH] Add and use CBlockIndexHeightOnlyComparator

...also use std::sort for clarity
---
 src/node/blockstorage.cpp | 11 +++++++----
 src/node/blockstorage.h   |  5 +++++
 src/validation.cpp        | 17 ++++++++---------
 3 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/src/node/blockstorage.cpp b/src/node/blockstorage.cpp
index bbdd240692..73bc4e0072 100644
--- a/src/node/blockstorage.cpp
+++ b/src/node/blockstorage.cpp
@@ -47,6 +47,11 @@ bool CBlockIndexWorkComparator::operator()(const CBlockIndex* pa, const CBlockIn
     return false;
 }
 
+bool CBlockIndexHeightOnlyComparator::operator()(const CBlockIndex* pa, const CBlockIndex* pb) const
+{
+    return pa->nHeight < pb->nHeight;
+}
+
 static FILE* OpenUndoFile(const FlatFilePos& pos, bool fReadOnly = false);
 static FlatFileSeq BlockFileSeq();
 static FlatFileSeq UndoFileSeq();
@@ -242,10 +247,8 @@ bool BlockManager::LoadBlockIndex(const Consensus::Params& consensus_params)
     for (auto& [_, block_index] : m_block_index) {
         vSortedByHeight.push_back(&block_index);
     }
-    sort(vSortedByHeight.begin(), vSortedByHeight.end(),
-         [](const CBlockIndex* pa, const CBlockIndex* pb) {
-             return pa->nHeight < pb->nHeight;
-         });
+    std::sort(vSortedByHeight.begin(), vSortedByHeight.end(),
+              CBlockIndexHeightOnlyComparator());
 
     for (CBlockIndex* pindex : vSortedByHeight) {
         if (ShutdownRequested()) return false;
diff --git a/src/node/blockstorage.h b/src/node/blockstorage.h
index d230bdd24b..0fd87ddaf1 100644
--- a/src/node/blockstorage.h
+++ b/src/node/blockstorage.h
@@ -62,6 +62,11 @@ struct CBlockIndexWorkComparator {
     bool operator()(const CBlockIndex* pa, const CBlockIndex* pb) const;
 };
 
+struct CBlockIndexHeightOnlyComparator {
+    /* Only compares the height of two block indices, doesn't try to tie-break */
+    bool operator()(const CBlockIndex* pa, const CBlockIndex* pb) const;
+};
+
 /**
  * Maintains a tree of blocks (stored in `m_block_index`) which is consulted
  * to determine where the most-work tip is.
diff --git a/src/validation.cpp b/src/validation.cpp
index eebb6773d4..2828b4ae98 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -65,21 +65,22 @@
 using node::BLOCKFILE_CHUNK_SIZE;
 using node::BlockManager;
 using node::BlockMap;
+using node::CBlockIndexHeightOnlyComparator;
 using node::CBlockIndexWorkComparator;
 using node::CCoinsStats;
 using node::CoinStatsHashType;
+using node::fHavePruned;
+using node::fImporting;
+using node::fPruneMode;
+using node::fReindex;
 using node::GetUTXOStats;
+using node::nPruneTarget;
 using node::OpenBlockFile;
 using node::ReadBlockFromDisk;
 using node::SnapshotMetadata;
 using node::UNDOFILE_CHUNK_SIZE;
 using node::UndoReadFromDisk;
 using node::UnlinkPrunedFiles;
-using node::fHavePruned;
-using node::fImporting;
-using node::fPruneMode;
-using node::fReindex;
-using node::nPruneTarget;
 
 #define MICRO 0.000001
 #define MILLI 0.001
@@ -4073,10 +4074,8 @@ bool ChainstateManager::LoadBlockIndex()
         for (auto& [_, block_index] : m_blockman.m_block_index) {
             vSortedByHeight.push_back(&block_index);
         }
-        sort(vSortedByHeight.begin(), vSortedByHeight.end(),
-             [](const CBlockIndex* pa, const CBlockIndex* pb) {
-                 return pa->nHeight < pb->nHeight;
-             });
+        std::sort(vSortedByHeight.begin(), vSortedByHeight.end(),
+                  CBlockIndexHeightOnlyComparator());
 
         // Find start of assumed-valid region.
         int first_assumed_valid_height = std::numeric_limits<int>::max();