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

pitrou · web-flow · commit c713837e91f3 · 2017-11-03T20:36:39.000+01:00
Bug report and patch by Jeroen Demeyer.. (cherry picked from commit f6f90ff)
diff --git 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
@@ -0,0 +1 @@
+Fix potential missed signal in signal.signal().
diff --git 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)

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+Fix potential missed signal in signal.signal().`