From 381db57b42acfd893788304ae9d5fb8d771355c9 Mon Sep 17 00:00:00 2001
From: arvidn <arvid@libtorrent.org>
Date: Wed, 8 Nov 2017 23:48:51 +0100
Subject: [PATCH] improve simulations by reseeding the random number generator.
 also erase all output in between iterations in test_error_handling

---
 simulation/test_error_handling.cpp | 30 +++++++++++++++++++++++++++++-
 simulation/utils.cpp               |  4 +++-
 test/main.cpp                      | 25 ++++++++++++++++++++++++-
 test/test.hpp                      |  1 +
 4 files changed, 57 insertions(+), 3 deletions(-)

diff --git a/simulation/test_error_handling.cpp b/simulation/test_error_handling.cpp
index 0b3ce3127..a5661b87c 100644
--- a/simulation/test_error_handling.cpp
+++ b/simulation/test_error_handling.cpp
@@ -40,6 +40,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/ip_filter.hpp"
 #include "libtorrent/alert_types.hpp"
 #include "libtorrent/aux_/proxy_settings.hpp"
+#include "libtorrent/random.hpp"
 #include "libtorrent/settings_pack.hpp"
 #include "simulator/simulator.hpp"
 #include "simulator/socks_server.hpp"
@@ -146,6 +147,9 @@ void* operator new(std::size_t sz)
 {
 	if (--g_alloc_counter == 0)
 	{
+		char stack[10000];
+		print_backtrace(stack, sizeof(stack), 40, nullptr);
+		std::printf("\n\nthrowing bad_alloc (as part of test)\n%s\n\n\n", stack);
 		throw std::bad_alloc();
 	}
 	return std::malloc(sz);
@@ -156,10 +160,19 @@ void operator delete(void* ptr) noexcept
 	std::free(ptr);
 }
 
-TORRENT_TEST(no_proxy_tcp)
+TORRENT_TEST(error_handling)
 {
 	for (int i = 0; i < 3000; ++i)
 	{
+		// this will clear the history of all output we've printed so far.
+		// if we encounter an error from now on, we'll only print the relevant
+		// iteration
+		reset_output();
+
+		// re-seed the random engine each iteration, to make the runs
+		// deterministic
+		lt::aux::random_engine().seed(0x82daf973);
+
 		std::printf("\n\n === ROUND %d ===\n\n", i);
 		try
 		{
@@ -174,10 +187,25 @@ TORRENT_TEST(no_proxy_tcp)
 		{
 			// this is kind of expected
 		}
+		catch (boost::system::system_error const& err)
+		{
+			TEST_ERROR("session constructor terminated with unexpected exception. \""
+				+ err.code().message() + "\" round: "
+				+ std::to_string(i));
+			break;
+		}
+		catch (std::exception const& err)
+		{
+			TEST_ERROR("session constructor terminated with unexpected exception. \""
+				+ std::string(err.what()) + "\" round: "
+				+ std::to_string(i));
+			break;
+		}
 		catch (...)
 		{
 			TEST_ERROR("session constructor terminated with unexpected exception. round: "
 				+ std::to_string(i));
+			break;
 		}
 		// if we didn't fail any allocations this run, there's no need to
 		// continue, we won't exercise any new code paths
diff --git a/simulation/utils.cpp b/simulation/utils.cpp
index 36e4de3f0..490809f08 100644
--- a/simulation/utils.cpp
+++ b/simulation/utils.cpp
@@ -124,11 +124,13 @@ void print_alerts(lt::session& ses
 {
 	lt::time_point start_time = lt::clock_type::now();
 
+	static std::vector<lt::alert*> alerts;
+
 	ses.set_alert_notify([&ses,start_time,on_alert] {
 		ses.get_io_service().post([&ses,start_time,on_alert] {
 
 		try {
-			std::vector<lt::alert*> alerts;
+			alerts.clear();
 			ses.pop_alerts(&alerts);
 
 			for (lt::alert const* a : alerts)
diff --git a/test/main.cpp b/test/main.cpp
index 53f2df390..df14c9be0 100644
--- a/test/main.cpp
+++ b/test/main.cpp
@@ -267,7 +267,25 @@ struct unit_directory_guard
 	}
 };
 
-EXPORT int main(int argc, char const* argv[])
+void EXPORT reset_output()
+{
+	if (current_test == nullptr || current_test->output == 0) return;
+	fflush(stdout);
+	fflush(stderr);
+	rewind(current_test->output);
+#ifdef TORRENT_WINDOWS
+	int const r = _chsize(fileno(current_test->output), 0);
+#else
+	int const r = ftruncate(fileno(current_test->output), 0);
+#endif
+	if (r != 0)
+	{
+		// this is best effort, it's not the end of the world if we fail
+		std::cerr << "ftruncate of temporary test output file failed: " << strerror(errno) << "\n";
+	}
+}
+
+int EXPORT main(int argc, char const* argv[])
 {
 	char const* executable = argv[0];
 	// skip executable name
@@ -443,6 +461,11 @@ EXPORT int main(int argc, char const* argv[])
 		try
 		{
 #endif
+
+#if defined TORRENT_BUILD_SIMULATOR
+			lt::aux::random_engine().seed(0x82daf973);
+#endif
+
 			_g_test_failures = 0;
 			(*t.fun)();
 #ifndef BOOST_NO_EXCEPTIONS
diff --git a/test/test.hpp b/test/test.hpp
index c26e6d7de..7a83dd523 100644
--- a/test/test.hpp
+++ b/test/test.hpp
@@ -73,6 +73,7 @@ POSSIBILITY OF SUCH DAMAGE.
 void EXPORT report_failure(char const* err, char const* file, int line);
 int EXPORT print_failures();
 int EXPORT test_counter();
+void EXPORT reset_output();
 
 typedef void (*unit_test_fun_t)();