bpo-33332: Add signal.valid_signals() (GH-6581)

Author: pitrou

Doc/library/signal.rst

@@ -216,6 +216,15 @@ The :mod:`signal` module defines the following functions:
    .. versionadded:: 3.8
 
 
+.. function:: valid_signals()
+
+   Return the set of valid signal numbers on this platform.  This can be
+   less than ``range(1, NSIG)`` if some signals are reserved by the system
+   for internal use.
+
+   .. versionadded:: 3.8
+
+
 .. function:: pause()
 
    Cause the process to sleep until a signal is received; the appropriate handler
@@ -268,8 +277,8 @@ The :mod:`signal` module defines the following functions:
      argument.
 
    *mask* is a set of signal numbers (e.g. {:const:`signal.SIGINT`,
-   :const:`signal.SIGTERM`}). Use ``range(1, signal.NSIG)`` for a full mask
-   including all signals.
+   :const:`signal.SIGTERM`}). Use :func:`~signal.valid_signals` for a full
+   mask including all signals.
 
    For example, ``signal.pthread_sigmask(signal.SIG_BLOCK, [])`` reads the
    signal mask of the calling thread.

Lib/asyncio/unix_events.py

@@ -167,8 +167,8 @@ def _check_signal(self, sig):
         if not isinstance(sig, int):
             raise TypeError(f'sig must be an int, not {sig!r}')
 
-        if not (1 <= sig < signal.NSIG):
-            raise ValueError(f'sig {sig} out of range(1, {signal.NSIG})')
+        if sig not in signal.valid_signals():
+            raise ValueError(f'invalid signal number {sig}')
 
     def _make_read_pipe_transport(self, pipe, protocol, waiter=None,
                                   extra=None):

Lib/multiprocessing/resource_sharer.py

@@ -136,7 +136,7 @@ def _start(self):
 
     def _serve(self):
         if hasattr(signal, 'pthread_sigmask'):
-            signal.pthread_sigmask(signal.SIG_BLOCK, range(1, signal.NSIG))
+            signal.pthread_sigmask(signal.SIG_BLOCK, signal.valid_signals())
         while 1:
             try:
                 with self._listener.accept() as conn:

Lib/signal.py

@@ -65,8 +65,7 @@ def pthread_sigmask(how, mask):
 if 'sigpending' in _globals:
     @_wraps(_signal.sigpending)
     def sigpending():
-        sigs = _signal.sigpending()
-        return set(_int_to_enum(x, Signals) for x in sigs)
+        return {_int_to_enum(x, Signals) for x in _signal.sigpending()}
 
 
 if 'sigwait' in _globals:
@@ -76,4 +75,11 @@ def sigwait(sigset):
         return _int_to_enum(retsig, Signals)
     sigwait.__doc__ = _signal.sigwait
 
+
+if 'valid_signals' in _globals:
+    @_wraps(_signal.valid_signals)
+    def valid_signals():
+        return {_int_to_enum(x, Signals) for x in _signal.valid_signals()}
+
+
 del _globals, _wraps

Lib/test/support/__init__.py

@@ -2810,7 +2810,7 @@ class SaveSignals:
     def __init__(self):
         import signal
         self.signal = signal
-        self.signals = list(range(1, signal.NSIG))
+        self.signals = signal.valid_signals()
         # SIGKILL and SIGSTOP signals cannot be ignored nor caught
         for signame in ('SIGKILL', 'SIGSTOP'):
             try:

Lib/test/test_asyncio/test_unix_events.py

@@ -69,6 +69,7 @@ def test_handle_signal_cancelled_handler(self):
     @mock.patch('asyncio.unix_events.signal')
     def test_add_signal_handler_setup_error(self, m_signal):
         m_signal.NSIG = signal.NSIG
+        m_signal.valid_signals = signal.valid_signals
         m_signal.set_wakeup_fd.side_effect = ValueError
 
         self.assertRaises(
@@ -96,6 +97,7 @@ async def simple_coroutine():
     @mock.patch('asyncio.unix_events.signal')
     def test_add_signal_handler(self, m_signal):
         m_signal.NSIG = signal.NSIG
+        m_signal.valid_signals = signal.valid_signals
 
         cb = lambda: True
         self.loop.add_signal_handler(signal.SIGHUP, cb)
@@ -106,6 +108,7 @@ def test_add_signal_handler(self, m_signal):
     @mock.patch('asyncio.unix_events.signal')
     def test_add_signal_handler_install_error(self, m_signal):
         m_signal.NSIG = signal.NSIG
+        m_signal.valid_signals = signal.valid_signals
 
         def set_wakeup_fd(fd):
             if fd == -1:
@@ -125,6 +128,7 @@ class Err(OSError):
     @mock.patch('asyncio.base_events.logger')
     def test_add_signal_handler_install_error2(self, m_logging, m_signal):
         m_signal.NSIG = signal.NSIG
+        m_signal.valid_signals = signal.valid_signals
 
         class Err(OSError):
             errno = errno.EINVAL
@@ -145,6 +149,7 @@ class Err(OSError):
             errno = errno.EINVAL
         m_signal.signal.side_effect = Err
         m_signal.NSIG = signal.NSIG
+        m_signal.valid_signals = signal.valid_signals
 
         self.assertRaises(
             RuntimeError,
@@ -156,6 +161,7 @@ class Err(OSError):
     @mock.patch('asyncio.unix_events.signal')
     def test_remove_signal_handler(self, m_signal):
         m_signal.NSIG = signal.NSIG
+        m_signal.valid_signals = signal.valid_signals
 
         self.loop.add_signal_handler(signal.SIGHUP, lambda: True)
 
@@ -170,6 +176,7 @@ def test_remove_signal_handler(self, m_signal):
     def test_remove_signal_handler_2(self, m_signal):
         m_signal.NSIG = signal.NSIG
         m_signal.SIGINT = signal.SIGINT
+        m_signal.valid_signals = signal.valid_signals
 
         self.loop.add_signal_handler(signal.SIGINT, lambda: True)
         self.loop._signal_handlers[signal.SIGHUP] = object()
@@ -187,6 +194,7 @@ def test_remove_signal_handler_2(self, m_signal):
     @mock.patch('asyncio.base_events.logger')
     def test_remove_signal_handler_cleanup_error(self, m_logging, m_signal):
         m_signal.NSIG = signal.NSIG
+        m_signal.valid_signals = signal.valid_signals
         self.loop.add_signal_handler(signal.SIGHUP, lambda: True)
 
         m_signal.set_wakeup_fd.side_effect = ValueError
@@ -197,6 +205,7 @@ def test_remove_signal_handler_cleanup_error(self, m_logging, m_signal):
     @mock.patch('asyncio.unix_events.signal')
     def test_remove_signal_handler_error(self, m_signal):
         m_signal.NSIG = signal.NSIG
+        m_signal.valid_signals = signal.valid_signals
         self.loop.add_signal_handler(signal.SIGHUP, lambda: True)
 
         m_signal.signal.side_effect = OSError
@@ -207,6 +216,7 @@ def test_remove_signal_handler_error(self, m_signal):
     @mock.patch('asyncio.unix_events.signal')
     def test_remove_signal_handler_error2(self, m_signal):
         m_signal.NSIG = signal.NSIG
+        m_signal.valid_signals = signal.valid_signals
         self.loop.add_signal_handler(signal.SIGHUP, lambda: True)
 
         class Err(OSError):
@@ -219,6 +229,7 @@ class Err(OSError):
     @mock.patch('asyncio.unix_events.signal')
     def test_close(self, m_signal):
         m_signal.NSIG = signal.NSIG
+        m_signal.valid_signals = signal.valid_signals
 
         self.loop.add_signal_handler(signal.SIGHUP, lambda: True)
         self.loop.add_signal_handler(signal.SIGCHLD, lambda: True)
@@ -236,6 +247,7 @@ def test_close(self, m_signal):
     @mock.patch('asyncio.unix_events.signal')
     def test_close_on_finalizing(self, m_signal, m_sys):
         m_signal.NSIG = signal.NSIG
+        m_signal.valid_signals = signal.valid_signals
         self.loop.add_signal_handler(signal.SIGHUP, lambda: True)
 
         self.assertEqual(len(self.loop._signal_handlers), 1)

Lib/test/test_signal.py

@@ -67,9 +67,28 @@ def test_interprocess_signal(self):
         script = os.path.join(dirname, 'signalinterproctester.py')
         assert_python_ok(script)
 
+    def test_valid_signals(self):
+        s = signal.valid_signals()
+        self.assertIsInstance(s, set)
+        self.assertIn(signal.Signals.SIGINT, s)
+        self.assertIn(signal.Signals.SIGALRM, s)
+        self.assertNotIn(0, s)
+        self.assertNotIn(signal.NSIG, s)
+        self.assertLess(len(s), signal.NSIG)
+
 
 @unittest.skipUnless(sys.platform == "win32", "Windows specific")
 class WindowsSignalTests(unittest.TestCase):
+
+    def test_valid_signals(self):
+        s = signal.valid_signals()
+        self.assertIsInstance(s, set)
+        self.assertGreaterEqual(len(s), 6)
+        self.assertIn(signal.Signals.SIGINT, s)
+        self.assertNotIn(0, s)
+        self.assertNotIn(signal.NSIG, s)
+        self.assertLess(len(s), signal.NSIG)
+
     def test_issue9324(self):
         # Updated for issue #10003, adding SIGBREAK
         handler = lambda x, y: None
@@ -922,6 +941,17 @@ def test_pthread_sigmask_arguments(self):
         self.assertRaises(TypeError, signal.pthread_sigmask, 1)
         self.assertRaises(TypeError, signal.pthread_sigmask, 1, 2, 3)
         self.assertRaises(OSError, signal.pthread_sigmask, 1700, [])
+        with self.assertRaises(ValueError):
+            signal.pthread_sigmask(signal.SIG_BLOCK, [signal.NSIG])
+
+    @unittest.skipUnless(hasattr(signal, 'pthread_sigmask'),
+                         'need signal.pthread_sigmask()')
+    def test_pthread_sigmask_valid_signals(self):
+        s = signal.pthread_sigmask(signal.SIG_BLOCK, signal.valid_signals())
+        self.addCleanup(signal.pthread_sigmask, signal.SIG_SETMASK, s)
+        # Get current blocked set
+        s = signal.pthread_sigmask(signal.SIG_UNBLOCK, signal.valid_signals())
+        self.assertLessEqual(s, signal.valid_signals())
 
     @unittest.skipUnless(hasattr(signal, 'pthread_sigmask'),
                          'need signal.pthread_sigmask()')

Misc/NEWS.d/next/Library/2018-04-23-21-41-30.bpo-33332.Y6OZ8Z.rst

@@ -0,0 +1,2 @@
+Add ``signal.valid_signals()`` to expose the POSIX sigfillset()
+functionality.

Modules/clinic/signalmodule.c.h

@@ -341,6 +341,31 @@ PyDoc_STRVAR(signal_sigwait__doc__,
 
 #endif /* defined(HAVE_SIGWAIT) */
 
+#if (defined(HAVE_SIGFILLSET) || defined(MS_WINDOWS))
+
+PyDoc_STRVAR(signal_valid_signals__doc__,
+"valid_signals($module, /)\n"
+"--\n"
+"\n"
+"Return a set of valid signal numbers on this platform.\n"
+"\n"
+"The signal numbers returned by this function can be safely passed to\n"
+"functions like `pthread_sigmask`.");
+
+#define SIGNAL_VALID_SIGNALS_METHODDEF    \
+    {"valid_signals", (PyCFunction)signal_valid_signals, METH_NOARGS, signal_valid_signals__doc__},
+
+static PyObject *
+signal_valid_signals_impl(PyObject *module);
+
+static PyObject *
+signal_valid_signals(PyObject *module, PyObject *Py_UNUSED(ignored))
+{
+    return signal_valid_signals_impl(module);
+}
+
+#endif /* (defined(HAVE_SIGFILLSET) || defined(MS_WINDOWS)) */
+
 #if defined(HAVE_SIGWAITINFO)
 
 PyDoc_STRVAR(signal_sigwaitinfo__doc__,
@@ -459,6 +484,10 @@ signal_pthread_kill(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
     #define SIGNAL_SIGWAIT_METHODDEF
 #endif /* !defined(SIGNAL_SIGWAIT_METHODDEF) */
 
+#ifndef SIGNAL_VALID_SIGNALS_METHODDEF
+    #define SIGNAL_VALID_SIGNALS_METHODDEF
+#endif /* !defined(SIGNAL_VALID_SIGNALS_METHODDEF) */
+
 #ifndef SIGNAL_SIGWAITINFO_METHODDEF
     #define SIGNAL_SIGWAITINFO_METHODDEF
 #endif /* !defined(SIGNAL_SIGWAITINFO_METHODDEF) */
@@ -470,4 +499,4 @@ signal_pthread_kill(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 #ifndef SIGNAL_PTHREAD_KILL_METHODDEF
     #define SIGNAL_PTHREAD_KILL_METHODDEF
 #endif /* !defined(SIGNAL_PTHREAD_KILL_METHODDEF) */
-/*[clinic end generated code: output=7b41486acf93aa8e input=a9049054013a1b77]*/
+/*[clinic end generated code: output=f35d79e0cfee3f1b input=a9049054013a1b77]*/

Modules/signalmodule.c

@@ -841,11 +841,21 @@ iterable_to_sigset(PyObject *iterable, sigset_t *mask)
         if (signum == -1 && PyErr_Occurred())
             goto error;
         if (0 < signum && signum < NSIG) {
-            /* bpo-33329: ignore sigaddset() return value as it can fail
-             * for some reserved signals, but we want the `range(1, NSIG)`
-             * idiom to allow selecting all valid signals.
-             */
-            (void) sigaddset(mask, (int)signum);
+            if (sigaddset(mask, (int)signum)) {
+                if (errno != EINVAL) {
+                    /* Probably impossible */
+                    PyErr_SetFromErrno(PyExc_OSError);
+                    goto error;
+                }
+                /* For backwards compatibility, allow idioms such as
+                 * `range(1, NSIG)` but warn about invalid signal numbers
+                 */
+                const char *msg =
+                    "invalid signal number %ld, please use valid_signals()";
+                if (PyErr_WarnFormat(PyExc_RuntimeWarning, 1, msg, signum)) {
+                    goto error;
+                }
+            }
         }
         else {
             PyErr_Format(PyExc_ValueError,
@@ -1001,6 +1011,47 @@ signal_sigwait(PyObject *module, PyObject *sigset)
 #endif   /* #ifdef HAVE_SIGWAIT */
 
 
+#if defined(HAVE_SIGFILLSET) || defined(MS_WINDOWS)
+
+/*[clinic input]
+signal.valid_signals
+
+Return a set of valid signal numbers on this platform.
+
+The signal numbers returned by this function can be safely passed to
+functions like `pthread_sigmask`.
+[clinic start generated code]*/
+
+static PyObject *
+signal_valid_signals_impl(PyObject *module)
+/*[clinic end generated code: output=1609cffbcfcf1314 input=86a3717ff25288f2]*/
+{
+#ifdef MS_WINDOWS
+#ifdef SIGBREAK
+    PyObject *tup = Py_BuildValue("(iiiiiii)", SIGABRT, SIGBREAK, SIGFPE,
+                                  SIGILL, SIGINT, SIGSEGV, SIGTERM);
+#else
+    PyObject *tup = Py_BuildValue("(iiiiii)", SIGABRT, SIGFPE, SIGILL,
+                                  SIGINT, SIGSEGV, SIGTERM);
+#endif
+    if (tup == NULL) {
+        return NULL;
+    }
+    PyObject *set = PySet_New(tup);
+    Py_DECREF(tup);
+    return set;
+#else
+    sigset_t mask;
+    if (sigemptyset(&mask) || sigfillset(&mask)) {
+        return PyErr_SetFromErrno(PyExc_OSError);
+    }
+    return sigset_to_set(mask);
+#endif
+}
+
+#endif   /* #if defined(HAVE_SIGFILLSET) || defined(MS_WINDOWS) */
+
+
 #if defined(HAVE_SIGWAITINFO) || defined(HAVE_SIGTIMEDWAIT)
 static int initialized;
 static PyStructSequence_Field struct_siginfo_fields[] = {
@@ -1225,6 +1276,9 @@ static PyMethodDef signal_methods[] = {
     SIGNAL_SIGWAIT_METHODDEF
     SIGNAL_SIGWAITINFO_METHODDEF
     SIGNAL_SIGTIMEDWAIT_METHODDEF
+#if defined(HAVE_SIGFILLSET) || defined(MS_WINDOWS)
+    SIGNAL_VALID_SIGNALS_METHODDEF
+#endif
     {NULL, NULL}           /* sentinel */
 };