bpo-30057: Fix potential missed signal in signal.signal(). (#4258)

Bug report and patch by Jeroen Demeyer.

diff --git a/Misc/ACKS b/Misc/ACKS
index 1bd3c047d89a00ffdea5517abeac4ea0f9298098..05113903f06de7a775b6639dae6a4e6f95b8501a 100644 (file)
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -362,6 +362,7 @@ 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 (file)
index 0000000..5740eb2
--- /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 d470727fb629dc06c1dba62c72bf2f5a068738b3..1023244b62666c07e96278257ecc41f2ce670fcc 100644 (file)
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -461,12 +461,15 @@ signal_signal_impl(PyObject *module, int signalnum, PyObject *handler)
     }
     else
         func = signal_handler;
+    /* Check for pending signals before changing signal handler */
+    if (PyErr_CheckSignals()) {
+        return NULL;
+    }
     if (PyOS_setsig(signalnum, func) == SIG_ERR) {
         PyErr_SetFromErrno(PyExc_OSError);
         return NULL;
     }
     old_handler = Handlers[signalnum].func;
-    _Py_atomic_store_relaxed(&Handlers[signalnum].tripped, 0);
     Py_INCREF(handler);
     Handlers[signalnum].func = handler;
     if (old_handler != NULL)