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// Copyright 2018-2024 Emil Dotchevski and Reverge Studios, Inc.
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
// This is a simple program that demonstrates the use of LEAF to transport error
// objects between threads, without using exception handling. See try_capture_all_exceptions.cpp
// for the version that uses exception handling.
#include <boost/leaf/config.hpp>
#if !BOOST_LEAF_CFG_CAPTURE
#include <iostream>
int main()
{
std::cout << "Unit test not applicable." << std::endl;
return 0;
}
#else
#include <boost/leaf.hpp>
#include <vector>
#include <string>
#include <future>
#include <iterator>
#include <iostream>
#include <algorithm>
#include <thread>
namespace leaf = boost::leaf;
// Define several error types.
struct e_thread_id { std::thread::id value; };
struct e_failure_info1 { std::string value; };
struct e_failure_info2 { int value; };
// A type that represents a successfully returned result from a task.
struct task_result { };
// This is our task function. It produces objects of type task_result, but it
// may fail.
leaf::result<task_result> task()
{
bool succeed = (rand()%4) != 0; //...at random.
if( succeed )
return { };
else
return leaf::new_error(
e_thread_id{std::this_thread::get_id()},
e_failure_info1{"info"},
e_failure_info2{42} );
};
int main()
{
int const task_count = 42;
// Container to collect the generated std::future objects.
std::vector<std::future<leaf::result<task_result>>> fut;
// Launch the tasks, but rather than launching the task function directly,
// we use leaf::try_capture_all: in case of a failure, the returned leaf::result<>
// will capture all error objects.
std::generate_n( std::back_inserter(fut), task_count,
[&]
{
return std::async(
std::launch::async,
[&]
{
return leaf::try_capture_all(task);
} );
} );
// Wait on the futures, get the task results, handle errors.
for( auto & f : fut )
{
f.wait();
leaf::try_handle_all(
[&]() -> leaf::result<void>
{
BOOST_LEAF_AUTO(r, f.get());
// Success! Use r to access task_result.
std::cout << "Success!" << std::endl;
(void) r; // Presumably we'll somehow use the task_result.
return { };
},
[]( e_failure_info1 const & v1, e_failure_info2 const & v2, e_thread_id const & tid )
{
std::cerr << "Error in thread " << tid.value << "! failure_info1: " << v1.value << ", failure_info2: " << v2.value << std::endl;
},
[]( leaf::diagnostic_info const & unmatched )
{
std::cerr <<
"Unknown failure detected" << std::endl <<
"Cryptic diagnostic information follows" << std::endl <<
unmatched;
} );
}
}
////////////////////////////////////////
#ifdef BOOST_LEAF_NO_EXCEPTIONS
namespace boost
{
[[noreturn]] void throw_exception( std::exception const & e )
{
std::cerr << "Terminating due to a C++ exception under BOOST_LEAF_NO_EXCEPTIONS: " << e.what();
std::terminate();
}
struct source_location;
[[noreturn]] void throw_exception( std::exception const & e, boost::source_location const & )
{
throw_exception(e);
}
}
#endif
#endif
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