Merge #21567: docs: fix various misleading comments

4eca20d6f7 [doc] correct comment about ATMPW (glozow)
8fa74aeb5b [doc] correct comment in chainparams (glozow)
2f8272c2a4 [doc] GetBestBlock() doesn't do nothing (gzhao408)

Pull request description:

  Came across a few misleading comments, wanted to fix them

ACKs for top commit:
  jnewbery:
    ACK 4eca20d6f7
  MarcoFalke:
    ACK 4eca20d6f7
  laanwj:
    Code review ACK 4eca20d6f7

Tree-SHA512: 5bef1f1e7703f304128cf0eb8945e139e031580c99062bbbe15bf4db8443c2ba5a8c65844833132e6646c8980c678fc1d2ab0c63e17105585d583570ee350fd0

src/chainparams.cpp

@@ -56,7 +56,7 @@ static CBlock CreateGenesisBlock(uint32_t nTime, uint32_t nNonce, uint32_t nBits
 }
 
 /**
- * Main network
+ * Main network on which people trade goods and services.
  */
 class CMainParams : public CChainParams {
 public:
@@ -173,7 +173,7 @@ public:
 };
 
 /**
- * Testnet (v3)
+ * Testnet (v3): public test network which is reset from time to time.
  */
 class CTestNetParams : public CChainParams {
 public:
@@ -266,7 +266,7 @@ public:
 };
 
 /**
- * Signet
+ * Signet: test network with an additional consensus parameter (see BIP325).
  */
 class SigNetParams : public CChainParams {
 public:
@@ -373,7 +373,8 @@ public:
 };
 
 /**
- * Regression test
+ * Regression test: intended for private networks only. Has minimal difficulty to ensure that
+ * blocks can be found instantly.
  */
 class CRegTestParams : public CChainParams {
 public:

src/chainparams.h

@@ -64,10 +64,7 @@ struct ChainTxData {
 
 /**
  * CChainParams defines various tweakable parameters of a given instance of the
- * Bitcoin system. There are three: the main network on which people trade goods
- * and services, the public test network which gets reset from time to time and
- * a regression test mode which is intended for private networks only. It has
- * minimal difficulty to ensure that blocks can be found instantly.
+ * Bitcoin system.
  */
 class CChainParams
 {

src/validation.cpp

@@ -690,7 +690,8 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
         }
     }
 
-    // Bring the best block into scope
+    // This is const, but calls into the back end CoinsViews. The CCoinsViewDB at the bottom of the
+    // hierarchy brings the best block into scope. See CCoinsViewDB::GetBestBlock().
     m_view.GetBestBlock();
 
     // we have all inputs cached now, so switch back to dummy (to protect
@@ -1099,9 +1100,9 @@ static MempoolAcceptResult AcceptToMemoryPoolWithTime(const CChainParams& chainp
     assert(std::addressof(::ChainstateActive()) == std::addressof(active_chainstate));
     const MempoolAcceptResult result = MemPoolAccept(pool, active_chainstate).AcceptSingleTransaction(tx, args);
     if (result.m_result_type != MempoolAcceptResult::ResultType::VALID) {
-        // Remove coins that were not present in the coins cache before calling ATMPW;
-        // this is to prevent memory DoS in case we receive a large number of
-        // invalid transactions that attempt to overrun the in-memory coins cache
+        // Remove coins that were not present in the coins cache before calling
+        // AcceptSingleTransaction(); this is to prevent memory DoS in case we receive a large
+        // number of invalid transactions that attempt to overrun the in-memory coins cache
         // (`CCoinsViewCache::cacheCoins`).
 
         for (const COutPoint& hashTx : coins_to_uncache)