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

2 files changed, 89 insertions, 6 deletions

diff --git a/Modules/clinic/signalmodule.c.h b/Modules/clinic/signalmodule.c.h
index 1c439716c4..eca2da10ad 100644
--- a/Modules/clinic/signalmodule.c.h
+++ b/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 @@ exit:
     #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 @@ exit:
 #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]*/
diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index 35fd87e2d1..003bbb60e3 100644
--- a/Modules/signalmodule.c
+++ b/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 */
 };