print peer logs directly into the allocation

include/libtorrent/alert_types.hpp

@@ -2150,6 +2150,10 @@ namespace libtorrent
 			, tcp::endpoint const& i, peer_id const& pi
 			, peer_log_alert::direction_t dir
 			, char const* event, char const* log);
+		peer_log_alert(aux::stack_allocator& alloc, torrent_handle const& h
+			, tcp::endpoint const& i, peer_id const& pi
+			, peer_log_alert::direction_t dir
+			, char const* event, char const* fmt, va_list v);
 
 		TORRENT_DEFINE_ALERT(peer_log_alert, 81)
 

include/libtorrent/stack_allocator.hpp

@@ -63,29 +63,48 @@ namespace libtorrent { namespace aux
 			return ret;
 		}
 
-		int copy_buffer(char const* buf, int size)
+		int format_string(char const* fmt, va_list v)
 		{
-			int ret = int(m_storage.size());
+			int const ret = int(m_storage.size());
+			m_storage.resize(ret + 512);
+
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wformat-nonliteral"
+#endif
+			int const len = std::vsnprintf(m_storage.data() + ret, 512, fmt, v);
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+
+			m_storage.resize(len > 512 ? 512 : len);
+			return ret;
+		}
+
+		int copy_buffer(char const* buf, int const size)
+		{
+			int const ret = int(m_storage.size());
 			m_storage.resize(ret + size);
 			memcpy(&m_storage[ret], buf, size);
 			return ret;
 		}
 
-		int allocate(int bytes)
+		int allocate(int const bytes)
 		{
+			TORRENT_ASSERT(bytes >= 0);
 			int ret = int(m_storage.size());
 			m_storage.resize(ret + bytes);
 			return ret;
 		}
 
-		char* ptr(int idx)
+		char* ptr(int const idx)
 		{
 			TORRENT_ASSERT(idx >= 0);
 			TORRENT_ASSERT(idx < int(m_storage.size()));
 			return &m_storage[idx];
 		}
 
-		char const* ptr(int idx) const
+		char const* ptr(int const idx) const
 		{
 			TORRENT_ASSERT(idx >= 0);
 			TORRENT_ASSERT(idx < int(m_storage.size()));

src/alert.cpp

@@ -1699,6 +1699,17 @@ namespace libtorrent {
 		, m_str_idx(alloc.copy_string(log))
 	{}
 
+	peer_log_alert::peer_log_alert(aux::stack_allocator& alloc
+		, torrent_handle const& h
+		, tcp::endpoint const& i, peer_id const& pi
+		, peer_log_alert::direction_t dir
+		, char const* event, char const* fmt, va_list v)
+		: peer_alert(alloc, h, i, pi)
+		, event_type(event)
+		, direction(dir)
+		, m_str_idx(alloc.format_string(fmt, v))
+	{}
+
 	char const* peer_log_alert::msg() const
 	{
 		return m_alloc.get().ptr(m_str_idx);

src/peer_connection.cpp

@@ -509,18 +509,15 @@ namespace libtorrent
 		va_list v;
 		va_start(v, fmt);
 
-		// TODO: it would be neat to be able to print this straight into the
-		// alert's stack allocator
-		char buf[512];
-		std::vsnprintf(buf, sizeof(buf), fmt, v);
-		va_end(v);
-
 		torrent_handle h;
 		boost::shared_ptr<torrent> t = m_torrent.lock();
 		if (t) h = t->get_handle();
 
 		m_ses.alerts().emplace_alert<peer_log_alert>(
-			h, m_remote, m_peer_id, direction, event, buf);
+			h, m_remote, m_peer_id, direction, event, fmt, v);
+
+		va_end(v);
+
 	}
 #endif