Merge #13480: Avoid copies in range-for loops and add a warning to detect them

d92204c900d55ebaf2af5c900162b3c2c8c296e2 build: add warning to detect hidden copies in range-for loops (Cory Fields)
466e16e0e8523909f9968c5823691b1d4a3d8175 cleanup: avoid hidden copies in range-for loops (Cory Fields)

Pull request description:

  Following-up on #13241, which was itself a follow-up of #12169.

  See title. Fixing these would otherwise be a continuous process, adding the warning should keep them from cropping up.

  Note that the warning seems to be Clang-only for now.

Tree-SHA512: ccfb769c3128b3f92c95715abcf21ee2496fe2aa384f80efead1529a28eeb56b98995b531b49a089f8142601389e63f7bb935963d724eacde4f5e1b4a024934b

configure.ac

@@ -301,6 +301,7 @@ if test "x$CXXFLAGS_overridden" = "xno"; then
   AX_CHECK_COMPILE_FLAG([-Wvla],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wvla"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wformat-security],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wformat-security"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wthread-safety-analysis],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wthread-safety-analysis"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wrange-loop-analysis],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wrange-loop-analysis"],,[[$CXXFLAG_WERROR]])
 
   ## Some compilers (gcc) ignore unknown -Wno-* options, but warn about all
   ## unknown options if any other warning is produced. Test the -Wfoo case, and

src/miner.cpp

@@ -209,7 +209,7 @@ bool BlockAssembler::TestPackage(uint64_t packageSize, int64_t packageSigOpsCost
 //   segwit activation)
 bool BlockAssembler::TestPackageTransactions(const CTxMemPool::setEntries& package)
 {
-    for (const CTxMemPool::txiter it : package) {
+    for (CTxMemPool::txiter it : package) {
         if (!IsFinalTx(it->GetTx(), nHeight, nLockTimeCutoff))
             return false;
         if (!fIncludeWitness && it->GetTx().HasWitness())
@@ -241,7 +241,7 @@ int BlockAssembler::UpdatePackagesForAdded(const CTxMemPool::setEntries& already
         indexed_modified_transaction_set &mapModifiedTx)
 {
     int nDescendantsUpdated = 0;
-    for (const CTxMemPool::txiter it : alreadyAdded) {
+    for (CTxMemPool::txiter it : alreadyAdded) {
         CTxMemPool::setEntries descendants;
         mempool.CalculateDescendants(it, descendants);
         // Insert all descendants (not yet in block) into the modified set

src/qt/platformstyle.cpp

@@ -46,7 +46,7 @@ void MakeSingleColorImage(QImage& img, const QColor& colorbase)
 QIcon ColorizeIcon(const QIcon& ico, const QColor& colorbase)
 {
     QIcon new_ico;
-    for (const QSize sz : ico.availableSizes())
+    for (const QSize& sz : ico.availableSizes())
     {
         QImage img(ico.pixmap(sz).toImage());
         MakeSingleColorImage(img, colorbase);

src/rpc/blockchain.cpp

@@ -853,7 +853,7 @@ static void ApplyStats(CCoinsStats &stats, CHashWriter& ss, const uint256& hash,
     ss << hash;
     ss << VARINT(outputs.begin()->second.nHeight * 2 + outputs.begin()->second.fCoinBase ? 1u : 0u);
     stats.nTransactions++;
-    for (const auto output : outputs) {
+    for (const auto& output : outputs) {
         ss << VARINT(output.first + 1);
         ss << output.second.out.scriptPubKey;
         ss << VARINT(output.second.out.nValue, VarIntMode::NONNEGATIVE_SIGNED);

src/txmempool.cpp

@@ -69,12 +69,12 @@ void CTxMemPool::UpdateForDescendants(txiter updateIt, cacheMap &cachedDescendan
         setAllDescendants.insert(cit);
         stageEntries.erase(cit);
         const setEntries &setChildren = GetMemPoolChildren(cit);
-        for (const txiter childEntry : setChildren) {
+        for (txiter childEntry : setChildren) {
             cacheMap::iterator cacheIt = cachedDescendants.find(childEntry);
             if (cacheIt != cachedDescendants.end()) {
                 // We've already calculated this one, just add the entries for this set
                 // but don't traverse again.
-                for (const txiter cacheEntry : cacheIt->second) {
+                for (txiter cacheEntry : cacheIt->second) {
                     setAllDescendants.insert(cacheEntry);
                 }
             } else if (!setAllDescendants.count(childEntry)) {

src/validation.cpp

@@ -651,7 +651,7 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
         view.SetBackend(viewMemPool);
 
         // do all inputs exist?
-        for (const CTxIn txin : tx.vin) {
+        for (const CTxIn& txin : tx.vin) {
             if (!pcoinsTip->HaveCoinInCache(txin.prevout)) {
                 coins_to_uncache.push_back(txin.prevout);
             }
@@ -957,7 +957,7 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
         }
 
         // Remove conflicting transactions from the mempool
-        for (const CTxMemPool::txiter it : allConflicting)
+        for (CTxMemPool::txiter it : allConflicting)
         {
             LogPrint(BCLog::MEMPOOL, "replacing tx %s with %s for %s BTC additional fees, %d delta bytes\n",
                     it->GetTx().GetHash().ToString(),

src/wallet/init.cpp

@@ -200,7 +200,7 @@ bool WalletInit::Verify() const
     // Keep track of each wallet absolute path to detect duplicates.
     std::set<fs::path> wallet_paths;
 
-    for (const auto wallet_file : wallet_files) {
+    for (const auto& wallet_file : wallet_files) {
         fs::path wallet_path = fs::absolute(wallet_file, GetWalletDir());
 
         if (!wallet_paths.insert(wallet_path).second) {