Merge #11132: Document assumptions that are being made to avoid NULL pointer dereferences

fdc3293 Document assumptions that are being made to avoid NULL pointer dereferences (practicalswift)

Pull request description:

  Document assumptions (via `assert(…)`:s) that are being made avoid `NULL` pointer dereferences.

  Rationale:
  * Make it clear to human reviewers and non-human static analyzers that what might look like potential `NULL` pointer dereferences are written the way they are intentionally (these cases are currently flagged by various static analyzers).

Tree-SHA512: b424328195e2680e1e4ec546298f718c49e5ad182147dc004de580693db1b50eec4065e1c4f232bdb302baa12954265a50ba21cb5ba4ff30248535b2de778672

src/qt/walletframe.cpp

@@ -7,6 +7,7 @@
 #include "bitcoingui.h"
 #include "walletview.h"
 
+#include <cassert>
 #include <cstdio>
 
 #include <QHBoxLayout>
@@ -69,6 +70,7 @@ bool WalletFrame::setCurrentWallet(const QString& name)
 
     WalletView *walletView = mapWalletViews.value(name);
     walletStack->setCurrentWidget(walletView);
+    assert(walletView);
     walletView->updateEncryptionStatus();
     return true;
 }

src/validation.cpp

@@ -1912,6 +1912,7 @@ static bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockInd
     // before the first had been spent.  Since those coinbases are sufficiently buried its no longer possible to create further
     // duplicate transactions descending from the known pairs either.
     // If we're on the known chain at height greater than where BIP34 activated, we can save the db accesses needed for the BIP30 check.
+    assert(pindex->pprev);
     CBlockIndex *pindexBIP34height = pindex->pprev->GetAncestor(chainparams.GetConsensus().BIP34Height);
     //Only continue to enforce if we're below BIP34 activation height or the block hash at that height doesn't correspond.
     fEnforceBIP30 = fEnforceBIP30 && (!pindexBIP34height || !(pindexBIP34height->GetBlockHash() == chainparams.GetConsensus().BIP34Hash));
@@ -2234,6 +2235,7 @@ static bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockInd
         if (!pblocktree->WriteTimestampIndex(CTimestampIndexKey(pindex->nTime, pindex->GetBlockHash())))
             return AbortNode(state, "Failed to write timestamp index");
 
+    assert(pindex->phashBlock);
     // add this block to the view's block chain
     view.SetBestBlock(pindex->GetBlockHash());
 

src/wallet/wallet.cpp

@@ -686,6 +686,7 @@ void CWallet::SyncMetaData(std::pair<TxSpends::iterator, TxSpends::iterator> ran
         const uint256& hash = it->second;
         CWalletTx* copyTo = &mapWallet[hash];
         if (copyFrom == copyTo) continue;
+        assert(copyFrom && "Oldest wallet transaction in range assumed to have been found.");
         if (!copyFrom->IsEquivalentTo(*copyTo)) continue;
         copyTo->mapValue = copyFrom->mapValue;
         copyTo->vOrderForm = copyFrom->vOrderForm;