Let the download list own its downloads through a shared pointer.

A multicall could then dispatch commands on an erased download.

src/command_events.cc

@@ -51,7 +51,7 @@ apply_on_ratio(const torrent::Object& rawArgs) {
         !(max_ratio > 0 && total_upload * 100 > total_done * max_ratio))
       continue;
 
-    downloads.push_back(*itr);
+    downloads.push_back(itr->get());
   }
 
   auto ratio_command = "group." + group_name + ".ratio.command";
@@ -173,7 +173,7 @@ apply_close_low_diskspace(int64_t arg, uint32_t skip_priority) {
 
   torrent::FileList::cache_list cache;
 
-  for (auto download : *control->core()->download_list()) {
+  for (const auto& download : *control->core()->download_list()) {
     if (!download->is_downloading())
       continue;
     if (download->priority() >= skip_priority)
@@ -240,15 +240,25 @@ d_multicall(const torrent::Object::list_type& args) {
 
   // Add some pre-parsing of the commands, so we don't spend time
   // parsing and searching command map for every single call.
-  std::vector<core::Download*> dlist((*view_itr)->begin_visible(), (*view_itr)->end_visible());
+  // Hold a reference to each download so a command that erases one does not
+  // leave the rest of the loop dispatching on freed memory.
+  core::View::base_type dlist((*view_itr)->begin_visible(), (*view_itr)->end_visible());
 
   torrent::Object             resultRaw = torrent::Object::create_list();
   torrent::Object::list_type& result = resultRaw.as_list();
 
-  for (auto download : dlist) {
+  for (const auto& download : dlist) {
+    if (download.use_count() == 1)
+      continue;
+
     torrent::Object::list_type& row = result.insert(result.end(), torrent::Object::create_list())->as_list();
 
     for (torrent::Object::list_const_iterator cItr = ++args.begin(); cItr != args.end(); cItr++) {
+      // A command may erase this download, which destroys the torrent object it
+      // wraps; the list dropping its reference is what tells us.
+      if (download.use_count() == 1)
+        break;
+
       auto& cmd = cItr->as_string();
       row.push_back(rpc::parse_command(rpc::make_target(download), cmd.c_str(), cmd.c_str() + cmd.size()).first);
     }
@@ -271,10 +281,12 @@ d_multicall_filtered(const torrent::Object::list_type& args) {
   if (view_itr == viewManager->end())
     throw torrent::input_error("Could not find view '" + arg->as_string() + "'.");
 
-  // Make a filtered copy of the current item list
+  // Make a filtered copy of the current item list, holding a reference to each
+  // download so a command that erases one cannot free it under us.
   core::View::base_type dlist;
   (*view_itr)->filter_by(*++arg, dlist);
 
+
   // Generate result by iterating over all items
   auto  resultRaw = torrent::Object::create_list();
   auto& result    = resultRaw.as_list();
@@ -282,11 +294,17 @@ d_multicall_filtered(const torrent::Object::list_type& args) {
   ++arg;  // skip to first command
 
   for (const auto& item : dlist) {
+    if (item.use_count() == 1)
+      continue;
+
     // Add empty row to result
     torrent::Object::list_type& row = result.insert(result.end(), torrent::Object::create_list())->as_list();
 
     // Call the provided commands and assemble their results
     for (torrent::Object::list_const_iterator command = arg; command != args.end(); command++) {
+      if (item.use_count() == 1)
+        break;
+
       auto& cmdstr = command->as_string();
       row.push_back(rpc::parse_command(rpc::make_target(item), cmdstr.c_str(), cmdstr.c_str() + cmdstr.size()).first);
     }

src/command_tracker.cc

@@ -68,11 +68,11 @@ apply_dht_add_node(const std::string& arg) {
 torrent::Object
 apply_enable_trackers(int64_t arg) {
   if (arg == 0) {
-    for (auto download : *control->core()->download_list())
+    for (const auto& download : *control->core()->download_list())
       download->tracker_controller().for_each([](auto& tracker) { tracker.disable(); });
 
   } else {
-    for (auto download : *control->core()->download_list())
+    for (const auto& download : *control->core()->download_list())
       download->tracker_controller().for_each([](auto& tracker) { tracker.enable(); });
   }
 

src/core/download.h

@@ -1,6 +1,7 @@
 #ifndef RTORRENT_CORE_DOWNLOAD_H
 #define RTORRENT_CORE_DOWNLOAD_H
 
+#include <memory>
 #include <torrent/common.h>
 #include <torrent/download.h>
 #include <torrent/download_info.h>

src/core/download_list.cc

@@ -37,7 +37,7 @@ namespace core {
 inline void
 DownloadList::check_contains([[maybe_unused]] Download* d) {
 #ifdef USE_EXTRA_DEBUG
-  if (std::find(begin(), end(), d) == end())
+  if (std::find_if(begin(), end(), [d](const auto& entry) { return entry.get() == d; }) == end())
     throw torrent::internal_error("DownloadList::check_contains(...) failed.");
 #endif
 }
@@ -54,7 +54,6 @@ DownloadList::clear() {
       base_type::pop_back();
 
       torrent::download_remove(*download->download());
-      delete download;
 
     } catch (torrent::internal_error& e) {
       lt_log_print(torrent::LOG_ERROR, "DownloadList::clear() failed to close or remove download: %s", e.what());
@@ -70,7 +69,7 @@ DownloadList::clear() {
 void
 DownloadList::session_save() {
   for (auto& download : *this)
-    session_thread::manager()->save_resume_download(download);
+    session_thread::manager()->save_resume_download(download.get());
 
   control->dht_manager()->save_dht_cache();
   control->ui()->save_input_history();
@@ -78,7 +77,7 @@ DownloadList::session_save() {
 
 DownloadList::iterator
 DownloadList::find(const torrent::HashString& hash) {
-  return std::find_if(begin(), end(), [hash](Download* d) { return hash == d->info()->hash(); });
+  return std::find_if(begin(), end(), [hash](const auto& d) { return hash == d->info()->hash(); });
 }
 
 DownloadList::iterator
@@ -91,14 +90,14 @@ DownloadList::find_hex(const char* hash) {
   if (torrent::utils::transform_from_hex(hash, hash + 40, key) != key.end())
     return end();
 
-  return std::find_if(begin(), end(), [key](Download* d) { return key == d->info()->hash(); });
+  return std::find_if(begin(), end(), [key](const auto& d) { return key == d->info()->hash(); });
 }
 
 Download*
 DownloadList::find_hex_ptr(const char* hash) {
   iterator itr = find_hex(hash);
 
-  return itr != end() ? *itr : NULL;
+  return itr != end() ? itr->get() : NULL;
 }
 
 Download*
@@ -159,7 +158,7 @@ DownloadList::create(std::istream* str, uint32_t tracker_key, bool printLog) {
 
 DownloadList::iterator
 DownloadList::insert(Download* download) {
-  iterator itr = base_type::insert(end(), download);
+  iterator itr = base_type::insert(end(), std::shared_ptr<Download>(download));
 
   lt_log_print_info(torrent::LOG_TORRENT_INFO, download->info(), "download_list", "Inserting download.");
 
@@ -170,7 +169,7 @@ DownloadList::insert(Download* download) {
     // This needs to be separated into two different calls to ensure
     // the download remains in the view.
     for (auto v : *control->view_manager())
-      v->insert(download);
+      v->insert(*itr);
     for (auto v : *control->view_manager())
       v->filter_download(download);
 
@@ -187,7 +186,7 @@ DownloadList::insert(Download* download) {
 
 void
 DownloadList::erase_ptr(Download* download) {
-  erase(std::find(begin(), end(), download));
+  erase(std::find_if(begin(), end(), [download](const auto& entry) { return entry.get() == download; }));
 }
 
 DownloadList::iterator
@@ -201,15 +200,14 @@ DownloadList::erase(iterator itr) {
   (*itr)->set_hash_failed(true);
 
   close(*itr);
-  session_thread::manager()->remove_download(*itr);
+  session_thread::manager()->remove_download(itr->get());
 
   DL_TRIGGER_EVENT(*itr, "event.download.erased");
 
   for (auto v : *control->view_manager())
-    v->erase(*itr);
+    v->erase(itr->get());
 
   torrent::download_remove(*(*itr)->download());
-  delete *itr;
 
   return base_type::erase(itr);
 }

src/core/download_list.h

@@ -3,6 +3,7 @@
 
 #include <iosfwd>
 #include <list>
+#include <memory>
 #include <string>
 
 namespace torrent {
@@ -20,9 +21,9 @@ class Download;
 //
 // Fix apply_on_ratio if the base_type is changed.
 
-class DownloadList : private std::list<Download*> {
+class DownloadList : private std::list<std::shared_ptr<Download>> {
 public:
-  typedef std::list<Download*>               base_type;
+  typedef std::list<std::shared_ptr<Download>> base_type;
 
   using base_type::iterator;
   using base_type::const_iterator;
@@ -64,6 +65,14 @@ public:
   bool                open(Download* d);
   void                open_throw(Download* d);
 
+  // Overloads for the list's own entries, so callers iterating it do not need
+  // to unwrap.
+  bool                open(const value_type& d)          { return open(d.get()); }
+  void                close(const value_type& d)         { close(d.get()); }
+  void                close_quick(const value_type& d)   { close_quick(d.get()); }
+  void                pause(const value_type& d)         { pause(d.get()); }
+  void                resume(const value_type& d)        { resume(d.get()); }
+
   void                close(Download* d);
   void                close_directly(Download* d);
   void                close_quick(Download* d);

src/core/manager.cc

@@ -154,10 +154,10 @@ Manager::cleanup() {
 void
 Manager::shutdown(bool force) {
   if (!force) {
-    for (auto d : *m_download_list)
-      m_download_list->pause_default(d);
+    for (const auto& d : *m_download_list)
+      m_download_list->pause_default(d.get());
   } else {
-    for (auto d : *m_download_list)
+    for (const auto& d : *m_download_list)
       m_download_list->close_quick(d);
   }
 }
@@ -405,7 +405,7 @@ Manager::receive_hashing_changed() {
       continue;
 
     try {
-      m_download_list->open_throw(*itr);
+      m_download_list->open_throw(itr->get());
 
       // Since the bitfield is allocated on loading of resume load or
       // hash start, and unallocated on close, we know that if it it

src/core/view.cc

@@ -16,10 +16,20 @@
 namespace core {
 
 // Also add focus thingie here?
+// Matches the list entry that owns a given download.
+inline auto
+entry_is(Download* download) {
+  return [download](const std::shared_ptr<Download>& entry) { return entry.get() == download; };
+}
+
 struct view_downloads_compare {
   view_downloads_compare(const torrent::Object& cmd) :
       m_command(cmd) {}
 
+  bool operator()(const std::shared_ptr<Download>& d1, const std::shared_ptr<Download>& d2) const {
+    return (*this)(d1.get(), d2.get());
+  }
+
   bool operator()(Download* d1, Download* d2) const {
     try {
       if (m_command.is_empty())
@@ -54,6 +64,10 @@ struct view_downloads_filter {
   view_downloads_filter(const torrent::Object& cmd, const torrent::Object& cmd2) :
       m_command(cmd), m_command2(cmd2) {}
 
+  bool operator()(const std::shared_ptr<Download>& d1) const {
+    return (*this)(d1.get());
+  }
+
   bool operator()(Download* d1) const {
     return this->evalCmd(m_command, d1) && this->evalCmd(m_command2, d1);
   }
@@ -152,7 +166,7 @@ View::initialize(const std::string& name) {
 
 void
 View::erase(Download* download) {
-  iterator itr = std::find(base_type::begin(), base_type::end(), download);
+  iterator itr = std::find_if(base_type::begin(), base_type::end(), entry_is(download));
 
   if (itr >= end_visible()) {
     erase_internal(itr);
@@ -165,22 +179,24 @@ View::erase(Download* download) {
 
 void
 View::set_visible(Download* download) {
-  iterator itr = std::find(begin_filtered(), end_filtered(), download);
+  iterator itr = std::find_if(begin_filtered(), end_filtered(), entry_is(download));
 
   if (itr == end_filtered())
     return;
 
   // Don't optimize erase since we want to keep the order of the
   // non-visible elements.
+  auto entry = *itr;
+
   base_type::erase(itr);
-  insert_visible(download);
+  insert_visible(entry);
 
   rpc::call_object_nothrow(m_event_added, rpc::make_target(download));
 }
 
 void
 View::set_not_visible(Download* download) {
-  iterator itr = std::find(begin_visible(), end_visible(), download);
+  iterator itr = std::find_if(begin_visible(), end_visible(), entry_is(download));
 
   if (itr == end_visible())
     return;
@@ -190,8 +206,10 @@ View::set_not_visible(Download* download) {
 
   // Don't optimize erase since we want to keep the order of the
   // non-visible elements.
+  auto entry = *itr;
+
   base_type::erase(itr);
-  base_type::push_back(download);
+  base_type::push_back(entry);
 
   rpc::call_object_nothrow(m_event_removed, rpc::make_target(download));
 }
@@ -241,12 +259,12 @@ View::prev_focus(unsigned int i) {
 
 void
 View::sort() {
-  Download* curFocus = focus() != end_visible() ? *focus() : NULL;
+  Download* curFocus = focus() != end_visible() ? focus()->get() : NULL;
 
   // Don't go randomly switching around equivalent elements.
   std::stable_sort(begin(), end_visible(), view_downloads_compare(m_sortCurrent));
 
-  m_focus = position(std::find(begin(), end_visible(), curFocus));
+  m_focus = position(std::find_if(begin(), end_visible(), entry_is(curFocus)));
   emit_changed();
 }
 
@@ -280,10 +298,10 @@ View::filter() {
   // set the elements to NULL as we trigger commands on them. Or
   // perhaps always clear them, thus not throwing anything.
   if (!m_event_removed.is_empty())
-    std::for_each(changed.begin(), splitChanged, std::bind(&rpc::call_object_d_nothrow, m_event_removed, std::placeholders::_1));
+    std::for_each(changed.begin(), splitChanged, [this](const auto& d) { rpc::call_object_d_nothrow(m_event_removed, d.get()); });
 
   if (!m_event_added.is_empty())
-    std::for_each(changed.begin(), splitChanged, std::bind(&rpc::call_object_d_nothrow, m_event_added, std::placeholders::_1));
+    std::for_each(changed.begin(), splitChanged, [this](const auto& d) { rpc::call_object_d_nothrow(m_event_added, d.get()); });
 
   emit_changed();
 }
@@ -294,21 +312,23 @@ View::filter_by(const torrent::Object& condition, View::base_type& result) {
   view_downloads_filter matches = view_downloads_filter(condition, m_temp_filter);
 
   for (iterator itr = begin_visible(); itr != end_visible(); ++itr)
-    if (matches(*itr))
+    if (matches(itr->get()))
       result.push_back(*itr);
 }
 
 void
 View::filter_download(core::Download* download) {
-  iterator itr = std::find(base_type::begin(), base_type::end(), download);
+  iterator itr = std::find_if(base_type::begin(), base_type::end(), entry_is(download));
 
   if (itr == base_type::end())
     throw torrent::internal_error("View::filter_download(...) could not find download.");
 
   if (view_downloads_filter(m_filter, m_temp_filter)(download)) {
     if (itr >= end_visible()) {
+      auto entry = *itr;
+
       erase_internal(itr);
-      insert_visible(download);
+      insert_visible(entry);
 
       rpc::call_object_nothrow(m_event_added, rpc::make_target(download));
 
@@ -317,16 +337,20 @@ View::filter_download(core::Download* download) {
       // already visible.
       //
       // Consider removing this.
+      auto entry = *itr;
+
       erase_internal(itr);
-      insert_visible(download);
+      insert_visible(entry);
     }
 
   } else {
     if (itr >= end_visible())
       return;
 
+    auto entry = *itr;
+
     erase_internal(itr);
-    base_type::push_back(download);
+    base_type::push_back(entry);
 
     rpc::call_object_nothrow(m_event_removed, rpc::make_target(download));
   }
@@ -345,8 +369,8 @@ View::clear_filter_on() {
 }
 
 inline void
-View::insert_visible(Download* d) {
-  auto itr = std::find_if(begin_visible(), end_visible(), [this, d](auto d2) { return view_downloads_compare(m_sortNew)(d, d2); });
+View::insert_visible(const std::shared_ptr<Download>& d) {
+  auto itr = std::find_if(begin_visible(), end_visible(), [this, &d](const auto& d2) { return view_downloads_compare(m_sortNew)(d.get(), d2.get()); });
 
   m_size++;
   m_focus += (m_focus >= position(itr));

src/core/view.h

@@ -15,6 +15,7 @@
 
 #include <functional>
 #include <list>
+#include <memory>
 #include <string>
 #include <vector>
 #include <torrent/object.h>
@@ -26,9 +27,9 @@ namespace core {
 
 class Download;
 
-class View : private std::vector<Download*> {
+class View : private std::vector<std::shared_ptr<Download>> {
 public:
-  typedef std::vector<Download*> base_type;
+  typedef std::vector<std::shared_ptr<Download>> base_type;
   typedef std::function<void()>  slot_void;
   typedef std::list<slot_void>   signal_void;
 
@@ -72,7 +73,7 @@ public:
     emit_changed();
   }
 
-  void insert(Download* download) { base_type::push_back(download); }
+  void insert(const std::shared_ptr<Download>& download) { base_type::push_back(download); }
   void erase(Download* download);
 
   void set_visible(Download* download);
@@ -124,9 +125,9 @@ private:
   View(const View&);
   void        operator=(const View&);
 
-  void        push_back(Download* d) { base_type::push_back(d); }
+  void        push_back(const std::shared_ptr<Download>& d) { base_type::push_back(d); }
 
-  inline void insert_visible(Download* d);
+  inline void insert_visible(const std::shared_ptr<Download>& d);
   inline void erase_internal(iterator itr);
 
   void        emit_changed();

src/display/window_download_list.cc

@@ -37,7 +37,7 @@ WindowDownloadList::set_view(core::View* l) {
 // Return a pair of ints, representing a) the ncurses attributes and b) the ncurses color pair ID to use
 std::pair<int, int>
 WindowDownloadList::get_attr_color(core::View::iterator selected) {
-  core::Download* item       = *selected;
+  core::Download* item       = selected->get();
   unsigned long   focus_attr = selected == m_view->focus() ? m_canvas->attr_map().at(RCOLOR_FOCUS) : 0;
   int             offset     = (((selected - m_view->begin_visible()) & 1) + 1) * RCOLOR_MAX; // Determine the even/odd offset for the color pair
   bool            active     = item->is_open() && item->is_active();
@@ -132,15 +132,15 @@ WindowDownloadList::redraw() {
       ColorKind focus_color = is_focused ? RCOLOR_FOCUS : RCOLOR_LABEL;
       auto      attr_color  = get_attr_color(range.first);
 
-      print_download_title(buffer.data(), last, *range.first);
+      print_download_title(buffer.data(), last, range.first->get());
       m_canvas->print(0, pos, "%c %s", focus_char, buffer.data());
       m_canvas->set_attr(2, pos++, -1, attr_color.first, attr_color.second);
 
-      print_download_info_full(buffer.data(), last, *range.first);
+      print_download_info_full(buffer.data(), last, range.first->get());
       m_canvas->print(0, pos, "%c %s", focus_char, buffer.data());
       m_canvas->set_attr(2, pos++, -1, focus_color);
 
-      print_download_status(buffer.data(), last, *range.first);
+      print_download_status(buffer.data(), last, range.first->get());
       m_canvas->print(0, pos, "%c %s", focus_char, buffer.data());
       m_canvas->set_attr(2, pos++, -1, focus_color);
 
@@ -152,7 +152,7 @@ WindowDownloadList::redraw() {
       char focus_char = range.first == m_view->focus() ? '*' : ' ';
       auto attr_color = get_attr_color(range.first);
 
-      print_download_info_compact(buffer.data(), last, *range.first);
+      print_download_info_compact(buffer.data(), last, range.first->get());
       m_canvas->print(0, pos, "%c %s", focus_char, buffer.data());
       m_canvas->set_attr(2, pos++, -1, attr_color.first, attr_color.second);
 

src/rpc/command_map.h

@@ -1,6 +1,7 @@
 #ifndef RTORRENT_RPC_COMMAND_MAP_H
 #define RTORRENT_RPC_COMMAND_MAP_H
 
+#include <memory>
 #include <map>
 #include <string>
 #include <cstring>
@@ -104,6 +105,10 @@ inline target_type make_target(T target) {
   return target_type((int)target_type_id<T>::value, target);
 }
 
+inline target_type make_target(const std::shared_ptr<core::Download>& target) {
+  return make_target(target.get());
+}
+
 template <typename T>
 inline target_type make_target_pair(T target1, T target2) {
   return target_type((int)target_type_id<T, T>::value, target1, target2);

src/ui/download.cc

@@ -1,3 +1,4 @@
+#include <memory>
 #include "config.h"
 
 #include <cassert>
@@ -30,8 +31,10 @@
 
 namespace ui {
 
-Download::Download(core::Download* d)
-  : m_download(d) {
+Download::Download(const std::shared_ptr<core::Download>& download)
+  : m_download(download.get()) {
+
+  auto* d = download.get();
 
   m_windowDownloadStatus = std::make_unique<WDownloadStatus>(d);
   m_windowDownloadStatus->set_bottom(true);

src/ui/download.h

@@ -2,6 +2,7 @@
 #define RTORRENT_UI_DOWNLOAD_H
 
 #include <list>
+#include <memory>
 #include <torrent/peer/peer.h>
 
 #include "display/manager.h"
@@ -36,7 +37,7 @@ public:
     DISPLAY_MAX_SIZE
   } Display;
 
-  Download(core::Download* d);
+  Download(const std::shared_ptr<core::Download>& d);
   ~Download();
 
   void                activate(display::Frame* frame, bool focus = true);

src/ui/download_list.cc

@@ -89,7 +89,7 @@ DownloadList::unfocus_download(core::Download* d) {
   if (m_state == DISPLAY_DOWNLOAD && d == static_cast<Download*>(m_uiArray[DISPLAY_DOWNLOAD])->download())
     activate_display(DISPLAY_DOWNLOAD_LIST);
 
-  if (current_view()->focus() < current_view()->end_visible() && *current_view()->focus() == d)
+  if (current_view()->focus() < current_view()->end_visible() && current_view()->focus()->get() == d)
       current_view()->next_focus();
 }
 

src/ui/element_download_list.cc

@@ -196,7 +196,7 @@ ElementDownloadList::receive_cycle_throttle() {
   if (m_view->focus() == m_view->end_visible())
     return;
 
-  core::Download* download = *m_view->focus();
+  core::Download* download = m_view->focus()->get();
   if (download->is_active()) {
     lt_log_print(torrent::LOG_TORRENT_WARN, "Cannot change throttle on active download.");
     return;