Issue #11393: Add the new faulthandler module

Modules/faulthandler.c

@@ -0,0 +1,971 @@
+#include "Python.h"
+#include "pythread.h"
+#include <signal.h>
+#include <object.h>
+#include <frameobject.h>
+#include <signal.h>
+
+#ifdef WITH_THREAD
+#  define FAULTHANDLER_LATER
+#endif
+
+#ifndef MS_WINDOWS
+   /* register() is useless on Windows, because only SIGSEGV and SIGILL can be
+      handled by the process, and these signals can only be used with enable(),
+      not using register() */
+#  define FAULTHANDLER_USER
+#endif
+
+#define PUTS(fd, str) write(fd, str, strlen(str))
+
+#ifdef HAVE_SIGACTION
+typedef struct sigaction _Py_sighandler_t;
+#else
+typedef PyOS_sighandler_t _Py_sighandler_t;
+#endif
+
+typedef struct {
+    int signum;
+    int enabled;
+    const char* name;
+    _Py_sighandler_t previous;
+    int all_threads;
+} fault_handler_t;
+
+static struct {
+    int enabled;
+    PyObject *file;
+    int fd;
+    int all_threads;
+} fatal_error = {0, NULL, -1, 0};
+
+#ifdef FAULTHANDLER_LATER
+static struct {
+    PyObject *file;
+    int fd;
+    PY_TIMEOUT_T timeout_ms;   /* timeout in microseconds */
+    int repeat;
+    volatile int running;
+    PyInterpreterState *interp;
+    int exit;
+    /* released by parent thread when cancel request */
+    PyThread_type_lock cancel_event;
+    /* released by child thread when joined */
+    PyThread_type_lock join_event;
+} thread;
+#endif
+
+#ifdef FAULTHANDLER_USER
+typedef struct {
+    int enabled;
+    PyObject *file;
+    int fd;
+    int all_threads;
+    _Py_sighandler_t previous;
+} user_signal_t;
+
+static user_signal_t *user_signals;
+
+/* the following macros come from Python: Modules/signalmodule.c */
+#if defined(PYOS_OS2) && !defined(PYCC_GCC)
+#define NSIG 12
+#endif
+#ifndef NSIG
+# if defined(_NSIG)
+#  define NSIG _NSIG            /* For BSD/SysV */
+# elif defined(_SIGMAX)
+#  define NSIG (_SIGMAX + 1)    /* For QNX */
+# elif defined(SIGMAX)
+#  define NSIG (SIGMAX + 1)     /* For djgpp */
+# else
+#  define NSIG 64               /* Use a reasonable default value */
+# endif
+#endif
+
+#endif /* FAULTHANDLER_USER */
+
+
+static fault_handler_t faulthandler_handlers[] = {
+#ifdef SIGBUS
+    {SIGBUS, 0, "Bus error", },
+#endif
+#ifdef SIGILL
+    {SIGILL, 0, "Illegal instruction", },
+#endif
+    {SIGFPE, 0, "Floating point exception", },
+    /* define SIGSEGV at the end to make it the default choice if searching the
+       handler fails in faulthandler_fatal_error() */
+    {SIGSEGV, 0, "Segmentation fault", }
+};
+static const unsigned char faulthandler_nsignals = \
+    sizeof(faulthandler_handlers) / sizeof(faulthandler_handlers[0]);
+
+#ifdef HAVE_SIGALTSTACK
+static stack_t stack;
+#endif
+
+
+/* Get the file descriptor of a file by calling its fileno() method and then
+   call its flush() method.
+
+   If file is NULL or Py_None, use sys.stderr as the new file.
+
+   On success, return the new file and write the file descriptor into *p_fd.
+   On error, return NULL. */
+
+static PyObject*
+faulthandler_get_fileno(PyObject *file, int *p_fd)
+{
+    PyObject *result;
+    long fd_long;
+    int fd;
+
+    if (file == NULL || file == Py_None) {
+        file = PySys_GetObject("stderr");
+        if (file == NULL) {
+            PyErr_SetString(PyExc_RuntimeError, "unable to get sys.stderr");
+            return NULL;
+        }
+    }
+
+    result = PyObject_CallMethod(file, "fileno", "");
+    if (result == NULL)
+        return NULL;
+
+    fd = -1;
+    if (PyLong_Check(result)) {
+        fd_long = PyLong_AsLong(result);
+        if (0 <= fd_long && fd_long < INT_MAX)
+            fd = (int)fd_long;
+    }
+    Py_DECREF(result);
+
+    if (fd == -1) {
+        PyErr_SetString(PyExc_RuntimeError,
+                        "file.fileno() is not a valid file descriptor");
+        return NULL;
+    }
+
+    result = PyObject_CallMethod(file, "flush", "");
+    if (result != NULL)
+        Py_DECREF(result);
+    else {
+        /* ignore flush() error */
+        PyErr_Clear();
+    }
+    *p_fd = fd;
+    return file;
+}
+
+static PyObject*
+faulthandler_dump_traceback_py(PyObject *self,
+                               PyObject *args, PyObject *kwargs)
+{
+    static char *kwlist[] = {"file", "all_threads", NULL};
+    PyObject *file = NULL;
+    int all_threads = 0;
+    PyThreadState *tstate;
+    const char *errmsg;
+    int fd;
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwargs,
+        "|Oi:dump_traceback", kwlist,
+        &file, &all_threads))
+        return NULL;
+
+    file = faulthandler_get_fileno(file, &fd);
+    if (file == NULL)
+        return NULL;
+
+    /* The caller holds the GIL and so PyThreadState_Get() can be used */
+    tstate = PyThreadState_Get();
+    if (tstate == NULL) {
+        PyErr_SetString(PyExc_RuntimeError,
+                        "unable to get the current thread state");
+        return NULL;
+    }
+
+    if (all_threads) {
+        errmsg = _Py_DumpTracebackThreads(fd, tstate->interp, tstate);
+        if (errmsg != NULL) {
+            PyErr_SetString(PyExc_RuntimeError, errmsg);
+            return NULL;
+        }
+    }
+    else {
+        _Py_DumpTraceback(fd, tstate);
+    }
+    Py_RETURN_NONE;
+}
+
+
+/* Handler of SIGSEGV, SIGFPE, SIGBUS and SIGILL signals.
+
+   Display the current Python traceback, restore the previous handler and call
+   the previous handler.
+
+   On Windows, don't call explictly the previous handler, because Windows
+   signal handler would not be called (for an unknown reason). The execution of
+   the program continues at faulthandler_fatal_error() exit, but the same
+   instruction will raise the same fault (signal), and so the previous handler
+   will be called.
+
+   This function is signal safe and should only call signal safe functions. */
+
+static void
+faulthandler_fatal_error(
+    int signum
+#ifdef HAVE_SIGACTION
+    , siginfo_t *siginfo, void *ucontext
+#endif
+)
+{
+    const int fd = fatal_error.fd;
+    unsigned int i;
+    fault_handler_t *handler = NULL;
+    PyThreadState *tstate;
+
+    if (!fatal_error.enabled)
+        return;
+
+    for (i=0; i < faulthandler_nsignals; i++) {
+        handler = &faulthandler_handlers[i];
+        if (handler->signum == signum)
+            break;
+    }
+    if (handler == NULL) {
+        /* faulthandler_nsignals == 0 (unlikely) */
+        return;
+    }
+
+    /* restore the previous handler */
+#ifdef HAVE_SIGACTION
+    (void)sigaction(handler->signum, &handler->previous, NULL);
+#else
+    (void)signal(handler->signum, handler->previous);
+#endif
+    handler->enabled = 0;
+
+    PUTS(fd, "Fatal Python error: ");
+    PUTS(fd, handler->name);
+    PUTS(fd, "\n\n");
+
+    /* SIGSEGV, SIGFPE, SIGBUS and SIGILL are synchronous signals and so are
+       delivered to the thread that caused the fault. Get the Python thread
+       state of the current thread.
+
+       PyThreadState_Get() doesn't give the state of the thread that caused the
+       fault if the thread released the GIL, and so this function cannot be
+       used. Read the thread local storage (TLS) instead: call
+       PyGILState_GetThisThreadState(). */
+    tstate = PyGILState_GetThisThreadState();
+    if (tstate == NULL)
+        return;
+
+    if (fatal_error.all_threads)
+        _Py_DumpTracebackThreads(fd, tstate->interp, tstate);
+    else
+        _Py_DumpTraceback(fd, tstate);
+
+#ifndef MS_WINDOWS
+    /* call the previous signal handler: it is called if we use sigaction()
+       thanks to SA_NODEFER flag, otherwise it is deferred */
+    raise(signum);
+#else
+    /* on Windows, don't call explictly the previous handler, because Windows
+       signal handler would not be called */
+#endif
+}
+
+/* Install handler for fatal signals (SIGSEGV, SIGFPE, ...). */
+
+static PyObject*
+faulthandler_enable(PyObject *self, PyObject *args, PyObject *kwargs)
+{
+    static char *kwlist[] = {"file", "all_threads", NULL};
+    PyObject *file = NULL;
+    int all_threads = 0;
+    unsigned int i;
+    fault_handler_t *handler;
+#ifdef HAVE_SIGACTION
+    struct sigaction action;
+#endif
+    int err;
+    int fd;
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwargs,
+        "|Oi:enable", kwlist, &file, &all_threads))
+        return NULL;
+
+    file = faulthandler_get_fileno(file, &fd);
+    if (file == NULL)
+        return NULL;
+
+    Py_XDECREF(fatal_error.file);
+    Py_INCREF(file);
+    fatal_error.file = file;
+    fatal_error.fd = fd;
+    fatal_error.all_threads = all_threads;
+
+    if (!fatal_error.enabled) {
+        fatal_error.enabled = 1;
+
+        for (i=0; i < faulthandler_nsignals; i++) {
+            handler = &faulthandler_handlers[i];
+#ifdef HAVE_SIGACTION
+            action.sa_sigaction = faulthandler_fatal_error;
+            sigemptyset(&action.sa_mask);
+            /* Do not prevent the signal from being received from within
+               its own signal handler */
+            action.sa_flags = SA_NODEFER;
+#ifdef HAVE_SIGALTSTACK
+            if (stack.ss_sp != NULL) {
+                /* Call the signal handler on an alternate signal stack
+                   provided by sigaltstack() */
+                action.sa_flags |= SA_ONSTACK;
+            }
+#endif
+            err = sigaction(handler->signum, &action, &handler->previous);
+#else
+            handler->previous = signal(handler->signum,
+                                       faulthandler_fatal_error);
+            err = (handler->previous == SIG_ERR);
+#endif
+            if (err) {
+                PyErr_SetFromErrno(PyExc_RuntimeError);
+                return NULL;
+            }
+            handler->enabled = 1;
+        }
+    }
+    Py_RETURN_NONE;
+}
+
+static void
+faulthandler_disable(void)
+{
+    unsigned int i;
+    fault_handler_t *handler;
+
+    if (fatal_error.enabled) {
+        fatal_error.enabled = 0;
+        for (i=0; i < faulthandler_nsignals; i++) {
+            handler = &faulthandler_handlers[i];
+            if (!handler->enabled)
+                continue;
+#ifdef HAVE_SIGACTION
+            (void)sigaction(handler->signum, &handler->previous, NULL);
+#else
+            (void)signal(handler->signum, handler->previous);
+#endif
+            handler->enabled = 0;
+        }
+    }
+
+    Py_CLEAR(fatal_error.file);
+}
+
+static PyObject*
+faulthandler_disable_py(PyObject *self)
+{
+    if (!fatal_error.enabled) {
+        Py_INCREF(Py_False);
+        return Py_False;
+    }
+    faulthandler_disable();
+    Py_INCREF(Py_True);
+    return Py_True;
+}
+
+static PyObject*
+faulthandler_is_enabled(PyObject *self)
+{
+    return PyBool_FromLong(fatal_error.enabled);
+}
+
+#ifdef FAULTHANDLER_LATER
+
+static void
+faulthandler_thread(void *unused)
+{
+    PyLockStatus st;
+    const char* errmsg;
+    PyThreadState *current;
+    int ok;
+
+    do {
+        st = PyThread_acquire_lock_timed(thread.cancel_event,
+                                         thread.timeout_ms, 0);
+        if (st == PY_LOCK_ACQUIRED) {
+            /* Cancelled by user */
+            break;
+        }
+        /* Timeout => dump traceback */
+        assert(st == PY_LOCK_FAILURE);
+
+        /* get the thread holding the GIL, NULL if no thread hold the GIL */
+        current = _Py_atomic_load_relaxed(&_PyThreadState_Current);
+
+        errmsg = _Py_DumpTracebackThreads(thread.fd, thread.interp, current);
+        ok = (errmsg == NULL);
+
+        if (thread.exit)
+            _exit(1);
+    } while (ok && thread.repeat);
+
+    /* The only way out */
+    thread.running = 0;
+    PyThread_release_lock(thread.join_event);
+    PyThread_release_lock(thread.cancel_event);
+}
+
+static void
+faulthandler_cancel_dump_traceback_later(void)
+{
+    if (thread.running) {
+        /* Notify cancellation */
+        PyThread_release_lock(thread.cancel_event);
+        /* Wait for thread to join */
+        PyThread_acquire_lock(thread.join_event, 1);
+        assert(thread.running == 0);
+        PyThread_release_lock(thread.join_event);
+    }
+    Py_CLEAR(thread.file);
+}
+
+static PyObject*
+faulthandler_dump_traceback_later(PyObject *self,
+                                  PyObject *args, PyObject *kwargs)
+{
+    static char *kwlist[] = {"timeout", "repeat", "file", "exit", NULL};
+    double timeout;
+    PY_TIMEOUT_T timeout_ms;
+    int repeat = 0;
+    PyObject *file = NULL;
+    int fd;
+    int exit = 0;
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwargs,
+        "d|iOi:dump_tracebacks_later", kwlist,
+        &timeout, &repeat, &file, &exit))
+        return NULL;
+    timeout *= 1e6;
+    if (timeout >= (double) PY_TIMEOUT_MAX) {
+        PyErr_SetString(PyExc_OverflowError,  "timeout value is too large");
+        return NULL;
+    }
+    timeout_ms = (PY_TIMEOUT_T)timeout;
+    if (timeout_ms <= 0) {
+        PyErr_SetString(PyExc_ValueError, "timeout must be greater than 0");
+        return NULL;
+    }
+
+    file = faulthandler_get_fileno(file, &fd);
+    if (file == NULL)
+        return NULL;
+
+    /* Cancel previous thread, if running */
+    faulthandler_cancel_dump_traceback_later();
+
+    Py_XDECREF(thread.file);
+    Py_INCREF(file);
+    thread.file = file;
+    thread.fd = fd;
+    thread.timeout_ms = timeout_ms;
+    thread.repeat = repeat;
+    thread.interp = PyThreadState_Get()->interp;
+    thread.exit = exit;
+
+    /* Arm these locks to serve as events when released */
+    PyThread_acquire_lock(thread.join_event, 1);
+    PyThread_acquire_lock(thread.cancel_event, 1);
+
+    thread.running = 1;
+    if (PyThread_start_new_thread(faulthandler_thread, NULL) == -1) {
+        thread.running = 0;
+        Py_CLEAR(thread.file);
+        PyErr_SetString(PyExc_RuntimeError,
+                        "unable to start watchdog thread");
+        return NULL;
+    }
+
+    Py_RETURN_NONE;
+}
+
+static PyObject*
+faulthandler_cancel_dump_traceback_later_py(PyObject *self)
+{
+    faulthandler_cancel_dump_traceback_later();
+    Py_RETURN_NONE;
+}
+#endif /* FAULTHANDLER_LATER */
+
+#ifdef FAULTHANDLER_USER
+/* Handler of user signals (e.g. SIGUSR1).
+
+   Dump the traceback of the current thread, or of all threads if
+   thread.all_threads is true.
+
+   This function is signal safe and should only call signal safe functions. */
+
+static void
+faulthandler_user(int signum)
+{
+    user_signal_t *user;
+    PyThreadState *tstate;
+
+    user = &user_signals[signum];
+    if (!user->enabled)
+        return;
+
+    /* PyThreadState_Get() doesn't give the state of the current thread if
+       the thread doesn't hold the GIL. Read the thread local storage (TLS)
+       instead: call PyGILState_GetThisThreadState(). */
+    tstate = PyGILState_GetThisThreadState();
+    if (tstate == NULL) {
+        /* unable to get the current thread, do nothing */
+        return;
+    }
+
+    if (user->all_threads)
+        _Py_DumpTracebackThreads(user->fd, tstate->interp, tstate);
+    else
+        _Py_DumpTraceback(user->fd, tstate);
+}
+
+static PyObject*
+faulthandler_register(PyObject *self,
+                      PyObject *args, PyObject *kwargs)
+{
+    static char *kwlist[] = {"signum", "file", "all_threads", NULL};
+    int signum;
+    PyObject *file = NULL;
+    int all_threads = 0;
+    int fd;
+    unsigned int i;
+    user_signal_t *user;
+    _Py_sighandler_t previous;
+#ifdef HAVE_SIGACTION
+    struct sigaction action;
+#endif
+    int err;
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwargs,
+        "i|Oi:register", kwlist,
+        &signum, &file, &all_threads))
+        return NULL;
+
+    if (signum < 1 || NSIG <= signum) {
+        PyErr_SetString(PyExc_ValueError, "signal number out of range");
+        return NULL;
+    }
+
+    for (i=0; i < faulthandler_nsignals; i++) {
+        if (faulthandler_handlers[i].signum == signum) {
+            PyErr_Format(PyExc_RuntimeError,
+                         "signal %i cannot be registered by register(), "
+                         "use enable() instead",
+                         signum);
+            return NULL;
+        }
+    }
+
+    file = faulthandler_get_fileno(file, &fd);
+    if (file == NULL)
+        return NULL;
+
+    if (user_signals == NULL) {
+        user_signals = calloc(NSIG, sizeof(user_signal_t));
+        if (user_signals == NULL)
+            return PyErr_NoMemory();
+    }
+    user = &user_signals[signum];
+
+    if (!user->enabled) {
+#ifdef HAVE_SIGACTION
+        action.sa_handler = faulthandler_user;
+        sigemptyset(&action.sa_mask);
+        /* if the signal is received while the kernel is executing a system
+           call, try to restart the system call instead of interrupting it and
+           return EINTR */
+        action.sa_flags = SA_RESTART;
+#ifdef HAVE_SIGALTSTACK
+        if (stack.ss_sp != NULL) {
+            /* Call the signal handler on an alternate signal stack
+               provided by sigaltstack() */
+            action.sa_flags |= SA_ONSTACK;
+        }
+#endif
+        err = sigaction(signum, &action, &previous);
+#else
+        previous = signal(signum, faulthandler_user);
+        err = (previous == SIG_ERR);
+#endif
+        if (err) {
+            PyErr_SetFromErrno(PyExc_OSError);
+            return NULL;
+        }
+    }
+
+    Py_XDECREF(user->file);
+    Py_INCREF(file);
+    user->file = file;
+    user->fd = fd;
+    user->all_threads = all_threads;
+    user->previous = previous;
+    user->enabled = 1;
+
+    Py_RETURN_NONE;
+}
+
+static int
+faulthandler_unregister(user_signal_t *user, int signum)
+{
+    if (user->enabled)
+        return 0;
+    user->enabled = 0;
+#ifdef HAVE_SIGACTION
+    (void)sigaction(signum, &user->previous, NULL);
+#else
+    (void)signal(signum, user->previous);
+#endif
+    Py_CLEAR(user->file);
+    user->fd = -1;
+    return 1;
+}
+
+static PyObject*
+faulthandler_unregister_py(PyObject *self, PyObject *args)
+{
+    int signum;
+    user_signal_t *user;
+    int change;
+
+    if (!PyArg_ParseTuple(args, "i:unregister", &signum))
+        return NULL;
+
+    if (signum < 1 || NSIG <= signum) {
+        PyErr_SetString(PyExc_ValueError, "signal number out of range");
+        return NULL;
+    }
+
+    user = &user_signals[signum];
+    change = faulthandler_unregister(user, signum);
+    return PyBool_FromLong(change);
+}
+#endif   /* FAULTHANDLER_USER */
+
+
+static PyObject *
+faulthandler_read_null(PyObject *self, PyObject *args)
+{
+    int *x = NULL, y;
+    int release_gil = 0;
+    if (!PyArg_ParseTuple(args, "|i:_read_null", &release_gil))
+        return NULL;
+    if (release_gil) {
+        Py_BEGIN_ALLOW_THREADS
+        y = *x;
+        Py_END_ALLOW_THREADS
+    } else
+        y = *x;
+    return PyLong_FromLong(y);
+
+}
+
+static PyObject *
+faulthandler_sigsegv(PyObject *self, PyObject *args)
+{
+#if defined(MS_WINDOWS)
+    /* faulthandler_fatal_error() restores the previous signal handler and then
+       gives back the execution flow to the program. In a normal case, the
+       SIGSEGV was raised by the kernel because of a fault, and so if the
+       program retries to execute the same instruction, the fault will be
+       raised again.
+
+       Here the fault is simulated by a fake SIGSEGV signal raised by the
+       application. We have to raise SIGSEGV at lease twice: once for
+       faulthandler_fatal_error(), and one more time for the previous signal
+       handler. */
+    while(1)
+        raise(SIGSEGV);
+#else
+    raise(SIGSEGV);
+#endif
+    Py_RETURN_NONE;
+}
+
+static PyObject *
+faulthandler_sigfpe(PyObject *self, PyObject *args)
+{
+    /* Do an integer division by zero: raise a SIGFPE on Intel CPU, but not on
+       PowerPC. Use volatile to disable compile-time optimizations. */
+    volatile int x = 1, y = 0, z;
+    z = x / y;
+    /* if the division by zero didn't raise a SIGFPE, raise it manually */
+    raise(SIGFPE);
+    Py_RETURN_NONE;
+}
+
+#ifdef SIGBUS
+static PyObject *
+faulthandler_sigbus(PyObject *self, PyObject *args)
+{
+    raise(SIGBUS);
+    Py_RETURN_NONE;
+}
+#endif
+
+#ifdef SIGILL
+static PyObject *
+faulthandler_sigill(PyObject *self, PyObject *args)
+{
+#if defined(MS_WINDOWS)
+    /* see faulthandler_sigsegv() for the explanation about while(1) */
+    while(1)
+        raise(SIGILL);
+#else
+    raise(SIGILL);
+#endif
+    Py_RETURN_NONE;
+}
+#endif
+
+static PyObject *
+faulthandler_fatal_error_py(PyObject *self, PyObject *args)
+{
+    char *message;
+    if (!PyArg_ParseTuple(args, "y:fatal_error", &message))
+        return NULL;
+    Py_FatalError(message);
+    Py_RETURN_NONE;
+}
+
+#if defined(HAVE_SIGALTSTACK) && defined(HAVE_SIGACTION)
+static PyObject *
+faulthandler_stack_overflow(PyObject *self)
+{
+    /* allocate 4096 bytes on the stack at each call */
+    unsigned char buffer[4096];
+    buffer[0] = 1;
+    buffer[4095] = 2;
+    faulthandler_stack_overflow(self);
+    return PyLong_FromLong(buffer[0] + buffer[4095]);
+}
+#endif
+
+
+static int
+faulthandler_traverse(PyObject *module, visitproc visit, void *arg)
+{
+#ifdef FAULTHANDLER_USER
+    unsigned int index;
+#endif
+
+#ifdef FAULTHANDLER_LATER
+    Py_VISIT(thread.file);
+#endif
+#ifdef FAULTHANDLER_USER
+    if (user_signals != NULL) {
+        for (index=0; index < NSIG; index++)
+            Py_VISIT(user_signals[index].file);
+    }
+#endif
+    Py_VISIT(fatal_error.file);
+    return 0;
+}
+
+PyDoc_STRVAR(module_doc,
+"faulthandler module.");
+
+static PyMethodDef module_methods[] = {
+    {"enable",
+     (PyCFunction)faulthandler_enable, METH_VARARGS|METH_KEYWORDS,
+     PyDoc_STR("enable(file=sys.stderr, all_threads=False): "
+               "enable the fault handler")},
+    {"disable", (PyCFunction)faulthandler_disable_py, METH_NOARGS,
+     PyDoc_STR("disable(): disable the fault handler")},
+    {"is_enabled", (PyCFunction)faulthandler_is_enabled, METH_NOARGS,
+     PyDoc_STR("is_enabled()->bool: check if the handler is enabled")},
+    {"dump_traceback",
+     (PyCFunction)faulthandler_dump_traceback_py, METH_VARARGS|METH_KEYWORDS,
+     PyDoc_STR("dump_traceback(file=sys.stderr, all_threads=False): "
+               "dump the traceback of the current thread, or of all threads "
+               "if all_threads is True, into file")},
+#ifdef FAULTHANDLER_LATER
+    {"dump_tracebacks_later",
+     (PyCFunction)faulthandler_dump_traceback_later, METH_VARARGS|METH_KEYWORDS,
+     PyDoc_STR("dump_tracebacks_later(timeout, repeat=False, file=sys.stderr):\n"
+               "dump the traceback of all threads in timeout seconds,\n"
+               "or each timeout seconds if repeat is True.")},
+    {"cancel_dump_tracebacks_later",
+     (PyCFunction)faulthandler_cancel_dump_traceback_later_py, METH_NOARGS,
+     PyDoc_STR("cancel_dump_tracebacks_later():\ncancel the previous call "
+               "to dump_tracebacks_later().")},
+#endif
+
+#ifdef FAULTHANDLER_USER
+    {"register",
+     (PyCFunction)faulthandler_register, METH_VARARGS|METH_KEYWORDS,
+     PyDoc_STR("register(signum, file=sys.stderr, all_threads=False): "
+               "register an handler for the signal 'signum': dump the "
+               "traceback of the current thread, or of all threads if "
+               "all_threads is True, into file")},
+    {"unregister",
+     faulthandler_unregister_py, METH_VARARGS|METH_KEYWORDS,
+     PyDoc_STR("unregister(signum): unregister the handler of the signal "
+                "'signum' registered by register()")},
+#endif
+
+    {"_read_null", faulthandler_read_null, METH_VARARGS,
+     PyDoc_STR("_read_null(release_gil=False): read from NULL, raise "
+               "a SIGSEGV or SIGBUS signal depending on the platform")},
+    {"_sigsegv", faulthandler_sigsegv, METH_VARARGS,
+     PyDoc_STR("_sigsegv(): raise a SIGSEGV signal")},
+    {"_sigfpe", (PyCFunction)faulthandler_sigfpe, METH_NOARGS,
+     PyDoc_STR("_sigfpe(): raise a SIGFPE signal")},
+#ifdef SIGBUS
+    {"_sigbus", (PyCFunction)faulthandler_sigbus, METH_NOARGS,
+     PyDoc_STR("_sigbus(): raise a SIGBUS signal")},
+#endif
+#ifdef SIGILL
+    {"_sigill", (PyCFunction)faulthandler_sigill, METH_NOARGS,
+     PyDoc_STR("_sigill(): raise a SIGILL signal")},
+#endif
+    {"_fatal_error", faulthandler_fatal_error_py, METH_VARARGS,
+     PyDoc_STR("_fatal_error(message): call Py_FatalError(message)")},
+#if defined(HAVE_SIGALTSTACK) && defined(HAVE_SIGACTION)
+    {"_stack_overflow", (PyCFunction)faulthandler_stack_overflow, METH_NOARGS,
+     PyDoc_STR("_stack_overflow(): recursive call to raise a stack overflow")},
+#endif
+    {NULL, NULL} /* terminator */
+};
+
+static struct PyModuleDef module_def = {
+    PyModuleDef_HEAD_INIT,
+    "faulthandler",
+    module_doc,
+    0, /* non negative size to be able to unload the module */
+    module_methods,
+    NULL,
+    faulthandler_traverse,
+    NULL,
+    NULL
+};
+
+PyMODINIT_FUNC
+PyInit_faulthandler(void)
+{
+    return PyModule_Create(&module_def);
+}
+
+/* Call faulthandler.enable() if PYTHONFAULTHANDLER environment variable is
+   defined, or if sys._xoptions has a 'faulthandler' key. */
+
+static int
+faulthandler_env_options(void)
+{
+    PyObject *xoptions, *key, *module, *res;
+    int enable;
+
+    if (!Py_GETENV("PYTHONFAULTHANDLER")) {
+        xoptions = PySys_GetXOptions();
+        if (xoptions == NULL)
+            return -1;
+
+        key = PyUnicode_FromString("faulthandler");
+        if (key == NULL)
+            return -1;
+
+        enable = PyDict_Contains(xoptions, key);
+        Py_DECREF(key);
+        if (!enable)
+            return 0;
+    }
+    else
+        enable = 1;
+
+    module = PyImport_ImportModule("faulthandler");
+    if (module == NULL) {
+        return -1;
+    }
+    res = PyObject_CallMethod(module, "enable", "");
+    Py_DECREF(module);
+    if (res == NULL)
+        return -1;
+    Py_DECREF(res);
+    return 0;
+}
+
+int _PyFaulthandler_Init(void)
+{
+#ifdef HAVE_SIGALTSTACK
+    int err;
+
+    /* Try to allocate an alternate stack for faulthandler() signal handler to
+     * be able to allocate memory on the stack, even on a stack overflow. If it
+     * fails, ignore the error. */
+    stack.ss_flags = 0;
+    stack.ss_size = SIGSTKSZ;
+    stack.ss_sp = PyMem_Malloc(stack.ss_size);
+    if (stack.ss_sp != NULL) {
+        err = sigaltstack(&stack, NULL);
+        if (err) {
+            PyMem_Free(stack.ss_sp);
+            stack.ss_sp = NULL;
+        }
+    }
+#endif
+#ifdef FAULTHANDLER_LATER
+    thread.running = 0;
+    thread.file = NULL;
+    thread.cancel_event = PyThread_allocate_lock();
+    thread.join_event = PyThread_allocate_lock();
+    if (!thread.cancel_event || !thread.join_event) {
+        PyErr_SetString(PyExc_RuntimeError,
+                        "could not allocate locks for faulthandler");
+        return -1;
+    }
+#endif
+
+    return faulthandler_env_options();
+}
+
+void _PyFaulthandler_Fini(void)
+{
+#ifdef FAULTHANDLER_USER
+    unsigned int i;
+#endif
+
+#ifdef FAULTHANDLER_LATER
+    /* later */
+    faulthandler_cancel_dump_traceback_later();
+    if (thread.cancel_event) {
+        PyThread_free_lock(thread.cancel_event);
+        thread.cancel_event = NULL;
+    }
+    if (thread.join_event) {
+        PyThread_free_lock(thread.join_event);
+        thread.join_event = NULL;
+    }
+#endif
+
+#ifdef FAULTHANDLER_USER
+    /* user */
+    if (user_signals != NULL) {
+        for (i=0; i < NSIG; i++)
+            faulthandler_unregister(&user_signals[i], i+1);
+        free(user_signals);
+        user_signals = NULL;
+    }
+#endif
+
+    /* fatal */
+    faulthandler_disable();
+#ifdef HAVE_SIGALTSTACK
+    if (stack.ss_sp != NULL) {
+        PyMem_Free(stack.ss_sp);
+        stack.ss_sp = NULL;
+    }
+#endif
+}