commit 75a3e3d5bc0be1ce41289b661e7c53039cf3d5ba
author Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> Mon Apr 23 12:42:26 2018 -0700
committer Antoine Pitrou <pitrou@free.fr> Mon Apr 23 21:42:26 2018 +0200
tree 15231e534f2f08c4532b962c87b62d26177d1739
parent 9fc998d761591f2741d8e94f5b3009c56ae83882

bpo-33329: Fix multiprocessing regression on newer glibcs (GH-6575) (GH-6579)

Starting with glibc 2.27.9000-xxx, sigaddset() can return EINVAL for some
reserved signal numbers between 1 and NSIG.  The `range(1, NSIG)` idiom
is commonly used to select all signals for blocking with `pthread_sigmask`.
So we ignore the sigaddset() return value until we expose sigfillset()
to provide a better idiom.
(cherry picked from commit 25038ecfb665bef641abf8cb61afff7505b0e008)

Co-authored-by: Antoine Pitrou <pitrou@free.fr>

Modules/signalmodule.c

diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index b553eed..aa224fd 100644
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -759,7 +759,6 @@
     int result = -1;
     PyObject *iterator, *item;
     long signum;
-    int err;
 
     sigemptyset(mask);
 
@@ -781,11 +780,14 @@
         Py_DECREF(item);
         if (signum == -1 && PyErr_Occurred())
             goto error;
-        if (0 < signum && signum < NSIG)
-            err = sigaddset(mask, (int)signum);
-        else
-            err = 1;
-        if (err) {
+        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);
+        }
+        else {
             PyErr_Format(PyExc_ValueError,
                          "signal number %ld out of range", signum);
             goto error;