libcruft-util/debug/system.cpp

/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2010-2019 Danny Robson <danny@nerdcruft.net>
 */

#include "./system.hpp"

#include "./assert.hpp"
#include "./debugger.hpp"
#include "./except.hpp"
#include "./crash.hpp"

#include "../backtrace.hpp"
#include "../log.hpp"

#include <cstdlib>


////////////////////////////////////////////////////////////////////////////////
static std::terminate_handler old_handler = nullptr;


//-----------------------------------------------------------------------------
static void abort_with_trace (void)
{
    // We used to trigger a breakpoint so that our debugger didn't just let the
    // child terminate (ie, the behaviour of CLion/Win32/GDB).
    //
    // But this might silently terminate the program instead of allowing us the
    // chance to dump a backtrace depending on the precise mechanism for
    // `breakpoint`; in particular SIGTRAP and SIGINT trigger this.
#if 0
    breakpoint ();
#endif

    // If we're here because of an exception we may as well rethrow and hope
    // that the system will print exception data during the abort process.
    //
    // But we can at least try to print anything derived from std::exception
    // (which is a likely guess) before we self-destruct.
    if (auto ptr = std::current_exception (); ptr) {
        try {
            std::rethrow_exception (ptr);
        } catch (std::exception const &x) {
            LOG_EMERGENCY ("unhandled exception: {}\n{}", x.what (), ::cruft::backtrace {});
        } catch (cruft::error const &x) {
            LOG_EMERGENCY ("unhandled exception: {}\n{}", x, ::cruft::backtrace {});
        } catch (...) {
            LOG_EMERGENCY ("unhandled exception\n{}", ::cruft::backtrace {});
        }
    } else {
        LOG_EMERGENCY ("aborting: {}", ::cruft::backtrace {});
    }

    old_handler ();
}


///////////////////////////////////////////////////////////////////////////////
void
cruft::debug::init (void)
{
    init_crash_handler ();

    old_handler = std::set_terminate (abort_with_trace);
    CHECK_NEQ (
        reinterpret_cast<void*> (old_handler),
        reinterpret_cast<void*> (abort_with_trace)
    );

    if (!debug_enabled && !getenv ("DEBUG"))
        return;

    LOG_DEBUG ("setting debug environment");
    enable_fpe ();
    force_console ();
    prepare_debugger ();

    if (getenv ("DEBUG_WAIT"))
        await_debugger ();
}