[Python-checkins] [2.7] bpo-30057: Fix potential missed signal in signal.signal(). (GH-4258) (#4263)

[Antoine Pitrou]

https://github.com/python/cpython/commit/c713837e91f39dc18740c74729cb7cebcf54fe6e
commit: c713837e91f39dc18740c74729cb7cebcf54fe6e
branch: 2.7
author: Antoine Pitrou <pitrou at free.fr>
committer: GitHub <noreply at github.com>
date: 2017-11-03T20:36:39+01:00
summary:

[2.7] bpo-30057: Fix potential missed signal in signal.signal(). (GH-4258) (#4263)

Bug report and patch by Jeroen Demeyer..
(cherry picked from commit f6f90ff079a22b79a58d47b6117cc8a8c7d366f3)

files:
A Misc/NEWS.d/next/Library/2017-11-03-19-11-43.bpo-30057.NCaijI.rst
M Misc/ACKS
M Modules/signalmodule.c

diff --git a/Misc/ACKS b/Misc/ACKS
index e076c32b14d..dc64293b696 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -324,6 +324,7 @@ Vincent Delft
 Arnaud Delobelle
 Konrad Delong
 Erik Demaine
+Jeroen Demeyer
 Martin Dengler
 John Dennis
 L. Peter Deutsch
diff --git a/Misc/NEWS.d/next/Library/2017-11-03-19-11-43.bpo-30057.NCaijI.rst b/Misc/NEWS.d/next/Library/2017-11-03-19-11-43.bpo-30057.NCaijI.rst
new file mode 100644
index 00000000000..5740eb2500f
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2017-11-03-19-11-43.bpo-30057.NCaijI.rst
@@ -0,0 +1 @@
+Fix potential missed signal in signal.signal().
diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index c7bf1f08534..ef70d10bb18 100644
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -317,12 +317,15 @@ signal_signal(PyObject *self, PyObject *args)
     }
     else
         func = signal_handler;
+    /* Check for pending signals before changing signal handler */
+    if (PyErr_CheckSignals()) {
+        return NULL;
+    }
     if (PyOS_setsig(sig_num, func) == SIG_ERR) {
         PyErr_SetFromErrno(PyExc_RuntimeError);
         return NULL;
     }
     old_handler = Handlers[sig_num].func;
-    Handlers[sig_num].tripped = 0;
     Py_INCREF(obj);
     Handlers[sig_num].func = obj;
     if (old_handler != NULL)