Stop adding more outputs than bulletproof allows

If more outputs are requested, they are split across
multiple transactions.

#7322

src/wallet/wallet2.cpp

@@ -9768,13 +9768,18 @@ std::vector<wallet2::pending_tx> wallet2::create_transactions_2(std::vector<cryp
 
     TX() : weight(0), needed_fee(0) {}
 
-    void add(const cryptonote::tx_destination_entry &de, uint64_t amount, unsigned int original_output_index, bool merge_destinations) {
+    /* Add an output to the transaction.
+     * Returns True if the output was added, False if there are no more available output slots.
+     */
+    bool add(const cryptonote::tx_destination_entry &de, uint64_t amount, unsigned int original_output_index, bool merge_destinations, size_t max_dsts) {
       if (merge_destinations)
       {
         std::vector<cryptonote::tx_destination_entry>::iterator i;
         i = std::find_if(dsts.begin(), dsts.end(), [&](const cryptonote::tx_destination_entry &d) { return !memcmp (&d.addr, &de.addr, sizeof(de.addr)); });
         if (i == dsts.end())
         {
+          if (dsts.size() >= max_dsts)
+            return false;
           dsts.push_back(de);
           i = dsts.end() - 1;
           i->amount = 0;
@@ -9787,12 +9792,15 @@ std::vector<wallet2::pending_tx> wallet2::create_transactions_2(std::vector<cryp
             std::string("original_output_index too large: ") + std::to_string(original_output_index) + " > " + std::to_string(dsts.size()));
         if (original_output_index == dsts.size())
         {
+          if (dsts.size() >= max_dsts)
+            return false;
           dsts.push_back(de);
           dsts.back().amount = 0;
         }
         THROW_WALLET_EXCEPTION_IF(memcmp(&dsts[original_output_index].addr, &de.addr, sizeof(de.addr)), error::wallet_internal_error, "Mismatched destination address");
         dsts[original_output_index].amount += amount;
       }
+      return true;
     }
   };
   std::vector<TX> txes;
@@ -10062,6 +10070,7 @@ std::vector<wallet2::pending_tx> wallet2::create_transactions_2(std::vector<cryp
     // clear any fake outs we'd already gathered, since we'll need a new set
     outs.clear();
 
+    bool out_slots_exhausted = false;
     if (adding_fee)
     {
       LOG_PRINT_L2("We need more fee, adding it to fee");
@@ -10074,20 +10083,32 @@ std::vector<wallet2::pending_tx> wallet2::create_transactions_2(std::vector<cryp
         // we can fully pay that destination
         LOG_PRINT_L2("We can fully pay " << get_account_address_as_str(m_nettype, dsts[0].is_subaddress, dsts[0].addr) <<
           " for " << print_money(dsts[0].amount));
-        tx.add(dsts[0], dsts[0].amount, original_output_index, m_merge_destinations);
+        if (!tx.add(dsts[0], dsts[0].amount, original_output_index, m_merge_destinations, BULLETPROOF_MAX_OUTPUTS-1))
+        {
+          LOG_PRINT_L2("Didn't pay: ran out of output slots");
+          out_slots_exhausted = true;
+          break;
+        }
         available_amount -= dsts[0].amount;
         dsts[0].amount = 0;
         pop_index(dsts, 0);
         ++original_output_index;
       }
 
-      if (available_amount > 0 && !dsts.empty() && estimate_tx_weight(use_rct, tx.selected_transfers.size(), fake_outs_count, tx.dsts.size()+1, extra.size(), bulletproof, clsag) < TX_WEIGHT_TARGET(upper_transaction_weight_limit)) {
+      if (!out_slots_exhausted && available_amount > 0 && !dsts.empty() && estimate_tx_weight(use_rct, tx.selected_transfers.size(), fake_outs_count, tx.dsts.size()+1, extra.size(), bulletproof, clsag) < TX_WEIGHT_TARGET(upper_transaction_weight_limit)) {
         // we can partially fill that destination
         LOG_PRINT_L2("We can partially pay " << get_account_address_as_str(m_nettype, dsts[0].is_subaddress, dsts[0].addr) <<
           " for " << print_money(available_amount) << "/" << print_money(dsts[0].amount));
-        tx.add(dsts[0], available_amount, original_output_index, m_merge_destinations);
-        dsts[0].amount -= available_amount;
-        available_amount = 0;
+        if (tx.add(dsts[0], available_amount, original_output_index, m_merge_destinations, BULLETPROOF_MAX_OUTPUTS-1))
+        {
+          dsts[0].amount -= available_amount;
+          available_amount = 0;
+        }
+        else
+        {
+          LOG_PRINT_L2("Didn't pay: ran out of output slots");
+          out_slots_exhausted = true;
+        }
       }
     }
 
@@ -10095,8 +10116,15 @@ std::vector<wallet2::pending_tx> wallet2::create_transactions_2(std::vector<cryp
     LOG_PRINT_L2("Considering whether to create a tx now, " << tx.selected_transfers.size() << " inputs, tx limit "
       << upper_transaction_weight_limit);
     bool try_tx = false;
+
+    // If the new transaction is full, create it and start a new one
+    if (out_slots_exhausted)
+    {
+      LOG_PRINT_L2("Transaction is full, will create it and start a new tx");
+      try_tx = true;
+    }
     // if we have preferred picks, but haven't yet used all of them, continue
-    if (preferred_inputs.empty())
+    else if (preferred_inputs.empty())
     {
       if (adding_fee)
       {