construct and destruct objects in stack allocations (alloca())

Author: arvidn

include/libtorrent/aux_/alloca.hpp

@@ -35,30 +35,76 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/config.hpp"
 #include "libtorrent/aux_/typed_span.hpp"
 #include "libtorrent/aux_/numeric_cast.hpp"
+#include <iterator> // for iterator_traits
+#include <memory> // for addressof
+
+namespace libtorrent { namespace aux {
+
+template<class ForwardIt>
+inline void uninitialized_default_construct(ForwardIt first, ForwardIt last)
+{
+	using Value = typename std::iterator_traits<ForwardIt>::value_type;
+	ForwardIt current = first;
+	try {
+		for (; current != last; ++current) {
+			::new (static_cast<void*>(std::addressof(*current))) Value;
+		}
+	}  catch (...) {
+		for (; first != current; ++first) {
+			first->~Value();
+		}
+		throw;
+	}
+}
+
+template <typename T>
+struct alloca_destructor
+{
+	span<T> objects;
+	~alloca_destructor()
+	{
+		for (auto& o : objects)
+		{
+			TORRENT_UNUSED(o);
+			o.~T();
+		}
+	}
+};
+
+}}
 
 #if defined TORRENT_WINDOWS || defined TORRENT_MINGW
 
 #include <malloc.h>
 #define TORRENT_ALLOCA(v, t, n) ::libtorrent::aux::typed_span<t> v; { \
 	std::size_t TORRENT_ALLOCA_size = ::libtorrent::aux::numeric_cast<std::size_t>(n); \
 	t* TORRENT_ALLOCA_tmp = static_cast<t*>(_alloca(sizeof(t) * TORRENT_ALLOCA_size)); \
-	v = ::libtorrent::aux::typed_span<t>(TORRENT_ALLOCA_tmp, TORRENT_ALLOCA_size); }
+	v = ::libtorrent::aux::typed_span<t>(TORRENT_ALLOCA_tmp, TORRENT_ALLOCA_size); \
+	::libtorrent::aux::uninitialized_default_construct(v.begin(), v.end()); \
+	} \
+	::libtorrent::aux::alloca_destructor<t> v##_destructor{v};
 
 #elif defined TORRENT_BSD
 
 #include <stdlib.h>
 #define TORRENT_ALLOCA(v, t, n) ::libtorrent::aux::typed_span<t> v; { \
 	std::size_t TORRENT_ALLOCA_size = ::libtorrent::aux::numeric_cast<std::size_t>(n); \
 	t* TORRENT_ALLOCA_tmp = static_cast<t*>(alloca(sizeof(t) * TORRENT_ALLOCA_size)); \
-	v = ::libtorrent::aux::typed_span<t>(TORRENT_ALLOCA_tmp, TORRENT_ALLOCA_size); }
+	v = ::libtorrent::aux::typed_span<t>(TORRENT_ALLOCA_tmp, TORRENT_ALLOCA_size); \
+	::libtorrent::aux::uninitialized_default_construct(v.begin(), v.end()); \
+	} \
+	::libtorrent::aux::alloca_destructor<t> v##_destructor{v};
 
 #else
 
 #include <alloca.h>
 #define TORRENT_ALLOCA(v, t, n) ::libtorrent::aux::typed_span<t> v; { \
 	std::size_t TORRENT_ALLOCA_size = ::libtorrent::aux::numeric_cast<std::size_t>(n); \
 	t* TORRENT_ALLOCA_tmp = static_cast<t*>(alloca(sizeof(t) * TORRENT_ALLOCA_size)); \
-	v = ::libtorrent::aux::typed_span<t>(TORRENT_ALLOCA_tmp, TORRENT_ALLOCA_size); }
+	v = ::libtorrent::aux::typed_span<t>(TORRENT_ALLOCA_tmp, TORRENT_ALLOCA_size); \
+	::libtorrent::aux::uninitialized_default_construct(v.begin(), v.end()); \
+	} \
+	::libtorrent::aux::alloca_destructor<t> v##_destructor{v};
 
 #endif
 

src/bdecode.cpp

@@ -102,6 +102,7 @@ namespace {
 
 	struct stack_frame
 	{
+		stack_frame() : token(0), state(0) {}
 		explicit stack_frame(int const t): token(std::uint32_t(t)), state(0) {}
 		// this is an index into m_tokens
 		std::uint32_t token:31;

test/Jamfile

@@ -143,7 +143,8 @@ test-suite libtorrent :
 		test_linked_list.cpp
 		test_stack_allocator.cpp
 		test_listen_socket.cpp
-		test_file_progress.cpp ]
+		test_file_progress.cpp
+		test_alloca.cpp ]
 
 	[ run test_piece_picker.cpp ]
 

test/Makefile.am

@@ -48,7 +48,8 @@ test_programs = \
   test_direct_dht            \
   test_ffs                   \
   test_session_params        \
-  test_span
+  test_span                  \
+  test_alloca
 
 if ENABLE_TESTS
 check_PROGRAMS = $(test_programs)
@@ -243,6 +244,7 @@ test_direct_dht_SOURCES = test_direct_dht.cpp
 test_ffs_SOURCES = test_ffs.cpp
 test_session_params_SOURCES = test_session_params.cpp
 test_span_SOURCES = test_span.cpp
+test_alloca_SOURCES = test_alloca.cpp
 
 LDADD = libtest.la $(top_builddir)/src/libtorrent-rasterbar.la
 

test/test_alloca.cpp

@@ -0,0 +1,73 @@
+/*
+
+Copyright (c) 2017, Arvid Norberg
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in
+      the documentation and/or other materials provided with the distribution.
+    * Neither the name of the author nor the names of its
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+
+*/
+
+#include "test.hpp"
+#include "libtorrent/aux_/alloca.hpp"
+
+using namespace lt;
+
+namespace {
+
+struct A
+{
+	int val = 1337;
+};
+
+int destructed = 0;
+
+struct B
+{
+	~B() { ++destructed; }
+};
+
+}
+
+TORRENT_TEST(alloca_construct)
+{
+	TORRENT_ALLOCA(vec, A, 13);
+
+	TEST_EQUAL(vec.size(), 13);
+	for (auto const& o : vec)
+	{
+		TEST_EQUAL(o.val, 1337);
+	}
+}
+
+TORRENT_TEST(alloca_destruct)
+{
+	{
+		destructed = 0;
+		TORRENT_ALLOCA(vec, B, 3);
+	}
+	TEST_EQUAL(destructed, 3);
+}
+

test/test_heterogeneous_queue.cpp

@@ -33,6 +33,8 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "test.hpp"
 #include "libtorrent/heterogeneous_queue.hpp"
 
+namespace {
+
 struct A
 {
 	int a;
@@ -143,6 +145,8 @@ struct G : A
 	std::int64_t g;
 };
 
+} // anonymous namespace
+
 // test emplace_back of heterogeneous types
 // and retrieval of their pointers
 TORRENT_TEST(emplace_back)