Issue #22018: On Windows, signal.set_wakeup_fd() now also supports sockets.

A side effect is that Python depends to the WinSock library.

Doc/c-api/exceptions.rst

@@ -443,13 +443,18 @@ in various ways.  There is a separate error indicator for each thread.
 
 .. c:function:: int PySignal_SetWakeupFd(int fd)
 
-   This utility function specifies a file descriptor to which a ``'\0'`` byte will
-   be written whenever a signal is received.  It returns the previous such file
-   descriptor.  The value ``-1`` disables the feature; this is the initial state.
+   This utility function specifies a file descriptor to which the signal number
+   is written as a single byte whenever a signal is received. *fd* must be
+   non-blocking. It returns the previous such file descriptor.
+
+   The value ``-1`` disables the feature; this is the initial state.
    This is equivalent to :func:`signal.set_wakeup_fd` in Python, but without any
    error checking.  *fd* should be a valid file descriptor.  The function should
    only be called from the main thread.
 
+   .. versionchanged:: 3.5
+      On Windows, the function now also supports socket handles.
+
 
 .. c:function:: PyObject* PyErr_NewException(char *name, PyObject *base, PyObject *dict)
 

Doc/library/signal.rst

@@ -318,6 +318,9 @@ The :mod:`signal` module defines the following functions:
    attempting to call it from other threads will cause a :exc:`ValueError`
    exception to be raised.
 
+   .. versionchanged:: 3.5
+      On Windows, the function now also supports socket handles.
+
 
 .. function:: siginterrupt(signalnum, flag)
 

Lib/test/test_signal.py

@@ -6,6 +6,7 @@ import gc
 import pickle
 import select
 import signal
+import socket
 import struct
 import subprocess
 import traceback
@@ -255,6 +256,13 @@ class WakeupFDTests(unittest.TestCase):
         self.assertRaises((ValueError, OSError),
                           signal.set_wakeup_fd, fd)
 
+    def test_invalid_socket(self):
+        sock = socket.socket()
+        fd = sock.fileno()
+        sock.close()
+        self.assertRaises((ValueError, OSError),
+                          signal.set_wakeup_fd, fd)
+
     def test_set_wakeup_fd_result(self):
         r1, w1 = os.pipe()
         self.addCleanup(os.close, r1)
@@ -268,6 +276,20 @@ class WakeupFDTests(unittest.TestCase):
         self.assertEqual(signal.set_wakeup_fd(-1), w2)
         self.assertEqual(signal.set_wakeup_fd(-1), -1)
 
+    def test_set_wakeup_fd_socket_result(self):
+        sock1 = socket.socket()
+        self.addCleanup(sock1.close)
+        fd1 = sock1.fileno()
+
+        sock2 = socket.socket()
+        self.addCleanup(sock2.close)
+        fd2 = sock2.fileno()
+
+        signal.set_wakeup_fd(fd1)
+        self.assertIs(signal.set_wakeup_fd(fd2), fd1)
+        self.assertIs(signal.set_wakeup_fd(-1), fd2)
+        self.assertIs(signal.set_wakeup_fd(-1), -1)
+
 
 @unittest.skipIf(sys.platform == "win32", "Not valid on Windows")
 class WakeupSignalTests(unittest.TestCase):
@@ -435,6 +457,90 @@ class WakeupSignalTests(unittest.TestCase):
         """,  signal.SIGUSR1, signal.SIGUSR2, ordered=False)
 
 
+@unittest.skipUnless(hasattr(socket, 'socketpair'), 'need socket.socketpair')
+class WakeupSocketSignalTests(unittest.TestCase):
+
+    @unittest.skipIf(_testcapi is None, 'need _testcapi')
+    def test_socket(self):
+        # use a subprocess to have only one thread
+        code = """if 1:
+        import signal
+        import socket
+        import struct
+        import _testcapi
+
+        signum = signal.SIGINT
+        signals = (signum,)
+
+        def handler(signum, frame):
+            pass
+
+        signal.signal(signum, handler)
+
+        read, write = socket.socketpair()
+        read.setblocking(False)
+        write.setblocking(False)
+        signal.set_wakeup_fd(write.fileno())
+
+        _testcapi.raise_signal(signum)
+
+        data = read.recv(1)
+        if not data:
+            raise Exception("no signum written")
+        raised = struct.unpack('B', data)
+        if raised != signals:
+            raise Exception("%r != %r" % (raised, signals))
+
+        read.close()
+        write.close()
+        """
+
+        assert_python_ok('-c', code)
+
+    @unittest.skipIf(_testcapi is None, 'need _testcapi')
+    def test_send_error(self):
+        # Use a subprocess to have only one thread.
+        if os.name == 'nt':
+            action = 'send'
+        else:
+            action = 'write'
+        code = """if 1:
+        import errno
+        import signal
+        import socket
+        import sys
+        import time
+        import _testcapi
+        from test.support import captured_stderr
+
+        signum = signal.SIGINT
+
+        def handler(signum, frame):
+            pass
+
+        signal.signal(signum, handler)
+
+        read, write = socket.socketpair()
+        read.setblocking(False)
+        write.setblocking(False)
+
+        signal.set_wakeup_fd(write.fileno())
+
+        # Close sockets: send() will fail
+        read.close()
+        write.close()
+
+        with captured_stderr() as err:
+            _testcapi.raise_signal(signum)
+
+        err = err.getvalue()
+        if ('Exception ignored when trying to {action} to the signal wakeup fd'
+            not in err):
+            raise AssertionError(err)
+        """.format(action=action)
+        assert_python_ok('-c', code)
+
+
 @unittest.skipIf(sys.platform == "win32", "Not valid on Windows")
 class SiginterruptTest(unittest.TestCase):
 
@@ -984,6 +1090,7 @@ def test_main():
     try:
         support.run_unittest(GenericTests, PosixTests, InterProcessSignalTests,
                              WakeupFDTests, WakeupSignalTests,
+                             WakeupSocketSignalTests,
                              SiginterruptTest, ItimerTest, WindowsSignalTests,
                              PendingSignalsTests)
     finally:

Misc/NEWS

@@ -113,6 +113,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #22018: On Windows, signal.set_wakeup_fd() now also supports sockets.
+  A side effect is that Python depends to the WinSock library.
+
 - Issue #22054: Add os.get_blocking() and os.set_blocking() functions to get
   and set the blocking mode of a file descriptor (False if the O_NONBLOCK flag
   is set, True otherwise). These functions are not available on Windows.

Modules/signalmodule.c

@@ -7,6 +7,9 @@
 #ifndef MS_WINDOWS
 #include "posixmodule.h"
 #endif
+#ifdef MS_WINDOWS
+#include "socketmodule.h"   /* needed for SOCKET_T */
+#endif
 
 #ifdef MS_WINDOWS
 #include <windows.h>
@@ -87,7 +90,20 @@ static volatile struct {
     PyObject *func;
 } Handlers[NSIG];
 
+#ifdef MS_WINDOWS
+#define INVALID_FD ((SOCKET_T)-1)
+
+static volatile struct {
+    SOCKET_T fd;
+    int use_send;
+    int send_err_set;
+    int send_errno;
+    int send_win_error;
+} wakeup = {INVALID_FD, 0, 0};
+#else
+#define INVALID_FD (-1)
 static volatile sig_atomic_t wakeup_fd = -1;
+#endif
 
 /* Speed up sigcheck() when none tripped */
 static volatile sig_atomic_t is_tripped = 0;
@@ -172,7 +188,7 @@ checksignals_witharg(void * unused)
 }
 
 static int
-report_wakeup_error(void *data)
+report_wakeup_write_error(void *data)
 {
     int save_errno = errno;
     errno = (int) (Py_intptr_t) data;
@@ -184,25 +200,86 @@ report_wakeup_error(void *data)
     return 0;
 }
 
+#ifdef MS_WINDOWS
+static int
+report_wakeup_send_error(void* Py_UNUSED(data))
+{
+    PyObject *res;
+
+    if (wakeup.send_win_error) {
+        /* PyErr_SetExcFromWindowsErr() invokes FormatMessage() which
+           recognizes the error codes used by both GetLastError() and
+           WSAGetLastError */
+        res = PyErr_SetExcFromWindowsErr(PyExc_OSError, wakeup.send_win_error);
+    }
+    else {
+        errno = wakeup.send_errno;
+        res = PyErr_SetFromErrno(PyExc_OSError);
+    }
+
+    assert(res == NULL);
+    wakeup.send_err_set = 0;
+
+    PySys_WriteStderr("Exception ignored when trying to send to the "
+                      "signal wakeup fd:\n");
+    PyErr_WriteUnraisable(NULL);
+
+    return 0;
+}
+#endif   /* MS_WINDOWS */
+
 static void
 trip_signal(int sig_num)
 {
     unsigned char byte;
-    int rc = 0;
+    int fd;
+    Py_ssize_t rc;
 
     Handlers[sig_num].tripped = 1;
-    if (wakeup_fd != -1) {
+
+#ifdef MS_WINDOWS
+    fd = Py_SAFE_DOWNCAST(wakeup.fd, SOCKET_T, int);
+#else
+    fd = wakeup_fd;
+#endif
+
+    if (fd != INVALID_FD) {
         byte = (unsigned char)sig_num;
-        while ((rc = write(wakeup_fd, &byte, 1)) == -1 && errno == EINTR);
-        if (rc == -1)
-            Py_AddPendingCall(report_wakeup_error, (void *) (Py_intptr_t) errno);
+#ifdef MS_WINDOWS
+        if (wakeup.use_send) {
+            do {
+                rc = send(fd, &byte, 1, 0);
+            } while (rc < 0 && errno == EINTR);
+
+            /* we only have a storage for one error in the wakeup structure */
+            if (rc < 0 && !wakeup.send_err_set) {
+                wakeup.send_err_set = 1;
+                wakeup.send_errno = errno;
+                wakeup.send_win_error = GetLastError();
+                Py_AddPendingCall(report_wakeup_send_error, NULL);
+            }
+        }
+        else
+#endif
+        {
+            byte = (unsigned char)sig_num;
+            do {
+                rc = write(fd, &byte, 1);
+            } while (rc < 0 && errno == EINTR);
+
+            if (rc < 0) {
+                Py_AddPendingCall(report_wakeup_write_error,
+                                  (void *)(Py_intptr_t)errno);
+            }
+        }
+    }
+
+    if (!is_tripped) {
+        /* Set is_tripped after setting .tripped, as it gets
+           cleared in PyErr_CheckSignals() before .tripped. */
+        is_tripped = 1;
+        Py_AddPendingCall(checksignals_witharg, NULL);
     }
-    if (is_tripped)
-        return;
-    /* Set is_tripped after setting .tripped, as it gets
-       cleared in PyErr_CheckSignals() before .tripped. */
-    is_tripped = 1;
-    Py_AddPendingCall(checksignals_witharg, NULL);
 }
 
 static void
@@ -426,10 +503,29 @@ signal_siginterrupt(PyObject *self, PyObject *args)
 static PyObject *
 signal_set_wakeup_fd(PyObject *self, PyObject *args)
 {
-    struct stat buf;
+#ifdef MS_WINDOWS
+    PyObject *fdobj;
+    SOCKET_T fd, old_fd;
+    int res;
+    int res_size = sizeof res;
+    PyObject *mod;
+    struct stat st;
+    int is_socket;
+
+    if (!PyArg_ParseTuple(args, "O:set_wakeup_fd", &fdobj))
+        return NULL;
+
+    fd = PyLong_AsSocket_t(fdobj);
+    if (fd == (SOCKET_T)(-1) && PyErr_Occurred())
+        return NULL;
+#else
     int fd, old_fd;
+    struct stat st;
+
     if (!PyArg_ParseTuple(args, "i:set_wakeup_fd", &fd))
         return NULL;
+#endif
+
 #ifdef WITH_THREAD
     if (PyThread_get_thread_ident() != main_thread) {
         PyErr_SetString(PyExc_ValueError,
@@ -438,28 +534,72 @@ signal_set_wakeup_fd(PyObject *self, PyObject *args)
     }
 #endif
 
+#ifdef MS_WINDOWS
+    is_socket = 0;
+    if (fd != INVALID_FD) {
+        /* Import the _socket module to call WSAStartup() */
+        mod = PyImport_ImportModuleNoBlock("_socket");
+        if (mod == NULL)
+            return NULL;
+        Py_DECREF(mod);
+
+        /* test the socket */
+        if (getsockopt(fd, SOL_SOCKET, SO_ERROR,
+                       (char *)&res, &res_size) != 0) {
+            int err = WSAGetLastError();
+            if (err != WSAENOTSOCK) {
+                PyErr_SetExcFromWindowsErr(PyExc_OSError, err);
+                return NULL;
+            }
+
+            if (!_PyVerify_fd(fd)) {
+                PyErr_SetString(PyExc_ValueError, "invalid fd");
+                return NULL;
+            }
+
+            if (fstat(fd, &st) != 0) {
+                PyErr_SetFromErrno(PyExc_OSError);
+                return NULL;
+            }
+        }
+        else
+            is_socket = 1;
+    }
+
+    old_fd = wakeup.fd;
+    wakeup.fd = fd;
+    wakeup.use_send = is_socket;
+
+    if (old_fd != INVALID_FD)
+        return PyLong_FromSocket_t(old_fd);
+    else
+        return PyLong_FromLong(-1);
+#else
     if (fd != -1) {
         if (!_PyVerify_fd(fd)) {
             PyErr_SetString(PyExc_ValueError, "invalid fd");
             return NULL;
         }
 
-        if (fstat(fd, &buf) != 0)
-            return PyErr_SetFromErrno(PyExc_OSError);
+        if (fstat(fd, &st) != 0) {
+            PyErr_SetFromErrno(PyExc_OSError);
+            return NULL;
+        }
     }
 
     old_fd = wakeup_fd;
     wakeup_fd = fd;
 
     return PyLong_FromLong(old_fd);
+#endif
 }
 
 PyDoc_STRVAR(set_wakeup_fd_doc,
 "set_wakeup_fd(fd) -> fd\n\
 \n\
-Sets the fd to be written to (with '\\0') when a signal\n\
+Sets the fd to be written to (with the signal number) when a signal\n\
 comes in.  A library can use this to wakeup select or poll.\n\
-The previous fd is returned.\n\
+The previous fd or -1 is returned.\n\
 \n\
 The fd must be non-blocking.");
 
@@ -467,10 +607,17 @@ The fd must be non-blocking.");
 int
 PySignal_SetWakeupFd(int fd)
 {
-    int old_fd = wakeup_fd;
+    int old_fd;
     if (fd < 0)
         fd = -1;
+
+#ifdef MS_WINDOWS
+    old_fd = Py_SAFE_DOWNCAST(wakeup.fd, SOCKET_T, int);
+    wakeup.fd = fd;
+#else
+    old_fd = wakeup_fd;
     wakeup_fd = fd;
+#endif
     return old_fd;
 }
 

PCbuild/pythoncore.vcxproj

@@ -176,7 +176,7 @@
       <Command>"$(SolutionDir)make_buildinfo.exe" Release "$(IntDir)\"</Command>
     </PreLinkEvent>
     <Link>
-      <AdditionalDependencies>$(IntDir)getbuildinfo.o;%(AdditionalDependencies)</AdditionalDependencies>
+      <AdditionalDependencies>$(IntDir)getbuildinfo.o;ws2_32.lib;%(AdditionalDependencies)</AdditionalDependencies>
       <OutputFile>$(OutDir)$(PyDllName).dll</OutputFile>
       <IgnoreSpecificDefaultLibraries>libc;%(IgnoreSpecificDefaultLibraries)</IgnoreSpecificDefaultLibraries>
       <BaseAddress>0x1e000000</BaseAddress>
@@ -212,7 +212,7 @@ IF %ERRORLEVEL% NEQ 0 (
       <Command>"$(SolutionDir)make_buildinfo.exe" Release "$(IntDir)\"</Command>
     </PreLinkEvent>
     <Link>
-      <AdditionalDependencies>$(IntDir)getbuildinfo.o;%(AdditionalDependencies)</AdditionalDependencies>
+      <AdditionalDependencies>$(IntDir)getbuildinfo.o;ws2_32.lib;%(AdditionalDependencies)</AdditionalDependencies>
       <IgnoreSpecificDefaultLibraries>libc;%(IgnoreSpecificDefaultLibraries)</IgnoreSpecificDefaultLibraries>
       <BaseAddress>0x1e000000</BaseAddress>
     </Link>
@@ -247,7 +247,7 @@ IF %ERRORLEVEL% NEQ 0 (
       <Command>"$(SolutionDir)make_buildinfo.exe" Debug "$(IntDir)"</Command>
     </PreLinkEvent>
     <Link>
-      <AdditionalDependencies>$(IntDir)getbuildinfo.o;%(AdditionalDependencies)</AdditionalDependencies>
+      <AdditionalDependencies>$(IntDir)getbuildinfo.o;ws2_32.lib;%(AdditionalDependencies)</AdditionalDependencies>
       <IgnoreSpecificDefaultLibraries>libc;%(IgnoreSpecificDefaultLibraries)</IgnoreSpecificDefaultLibraries>
       <BaseAddress>0x1e000000</BaseAddress>
     </Link>
@@ -285,7 +285,7 @@ IF %ERRORLEVEL% NEQ 0 (
       <Command>"$(SolutionDir)make_buildinfo.exe" Debug "$(IntDir)"</Command>
     </PreLinkEvent>
     <Link>
-      <AdditionalDependencies>$(IntDir)getbuildinfo.o;%(AdditionalDependencies)</AdditionalDependencies>
+      <AdditionalDependencies>$(IntDir)getbuildinfo.o;ws2_32.lib;%(AdditionalDependencies)</AdditionalDependencies>
       <IgnoreSpecificDefaultLibraries>libc;%(IgnoreSpecificDefaultLibraries)</IgnoreSpecificDefaultLibraries>
       <BaseAddress>0x1e000000</BaseAddress>
     </Link>
@@ -317,7 +317,7 @@ IF %ERRORLEVEL% NEQ 0 (
       <Command>"$(SolutionDir)make_buildinfo.exe" Release "$(IntDir)\"</Command>
     </PreLinkEvent>
     <Link>
-      <AdditionalDependencies>$(IntDir)getbuildinfo.o;%(AdditionalDependencies)</AdditionalDependencies>
+      <AdditionalDependencies>$(IntDir)getbuildinfo.o;ws2_32.lib;%(AdditionalDependencies)</AdditionalDependencies>
       <OutputFile>$(OutDir)$(PyDllName).dll</OutputFile>
       <IgnoreSpecificDefaultLibraries>libc;%(IgnoreSpecificDefaultLibraries)</IgnoreSpecificDefaultLibraries>
       <BaseAddress>0x1e000000</BaseAddress>
@@ -353,7 +353,7 @@ IF %ERRORLEVEL% NEQ 0 (
       <Command>"$(SolutionDir)make_buildinfo.exe" Release "$(IntDir)\"</Command>
     </PreLinkEvent>
     <Link>
-      <AdditionalDependencies>$(IntDir)getbuildinfo.o;%(AdditionalDependencies)</AdditionalDependencies>
+      <AdditionalDependencies>$(IntDir)getbuildinfo.o;ws2_32.lib;%(AdditionalDependencies)</AdditionalDependencies>
       <IgnoreSpecificDefaultLibraries>libc;%(IgnoreSpecificDefaultLibraries)</IgnoreSpecificDefaultLibraries>
       <BaseAddress>0x1e000000</BaseAddress>
       <TargetMachine>MachineX64</TargetMachine>
@@ -386,7 +386,7 @@ IF %ERRORLEVEL% NEQ 0 (
       <Command>"$(SolutionDir)make_buildinfo.exe" Release "$(IntDir)\"</Command>
     </PreLinkEvent>
     <Link>
-      <AdditionalDependencies>$(IntDir)getbuildinfo.o;%(AdditionalDependencies)</AdditionalDependencies>
+      <AdditionalDependencies>$(IntDir)getbuildinfo.o;ws2_32.lib;%(AdditionalDependencies)</AdditionalDependencies>
       <OutputFile>$(OutDir)$(PyDllName).dll</OutputFile>
       <IgnoreSpecificDefaultLibraries>libc;%(IgnoreSpecificDefaultLibraries)</IgnoreSpecificDefaultLibraries>
       <BaseAddress>0x1e000000</BaseAddress>
@@ -422,7 +422,7 @@ IF %ERRORLEVEL% NEQ 0 (
       <Command>"$(SolutionDir)make_buildinfo.exe" Release "$(IntDir)\"</Command>
     </PreLinkEvent>
     <Link>
-      <AdditionalDependencies>$(IntDir)getbuildinfo.o;%(AdditionalDependencies)</AdditionalDependencies>
+      <AdditionalDependencies>$(IntDir)getbuildinfo.o;ws2_32.lib;%(AdditionalDependencies)</AdditionalDependencies>
       <IgnoreSpecificDefaultLibraries>libc;%(IgnoreSpecificDefaultLibraries)</IgnoreSpecificDefaultLibraries>
       <BaseAddress>0x1e000000</BaseAddress>
       <TargetMachine>MachineX64</TargetMachine>