shiboken: Fix race condition with unprotected Py_INCREFs

The signalmanager module contains a PyObjectWrapper object
into which PySide::SignalManager::qt_metacall calls via many
hard-to-track indirections.

Finding this problem was quite tricky. It was done by modifying
the Py_INCREF and Py_DECREF macros of a debug Python
interpreter and using the new PyGILState_Check function to
provoke a crash if the GIL was not held.

See the online documentation for details.

Change-Id: Ida8246c97dcf6443ff057d206a42d22e462f1913
Fixes: PYSIDE-813
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

1 files changed, 7 insertions, 0 deletions

diff --git a/sources/pyside2/libpyside/signalmanager.cpp b/sources/pyside2/libpyside/signalmanager.cpp
index 0fe0d0092..8e8cc9f02 100644
--- a/sources/pyside2/libpyside/signalmanager.cpp
+++ b/sources/pyside2/libpyside/signalmanager.cpp
@@ -114,18 +114,24 @@ namespace PySide {
 PyObjectWrapper::PyObjectWrapper()
     :m_me(Py_None)
 {
+    // PYSIDE-813: When PYSIDE-164 was solved by adding some thread allowance,
+    // this code was no longer protected. It was hard to find this connection.
+    // See the website https://bugreports.qt.io/browse/PYSIDE-813 for details.
+    Shiboken::GilState gil;
     Py_XINCREF(m_me);
 }
 
 PyObjectWrapper::PyObjectWrapper(PyObject *me)
     : m_me(me)
 {
+    Shiboken::GilState gil;
     Py_XINCREF(m_me);
 }
 
 PyObjectWrapper::PyObjectWrapper(const PyObjectWrapper &other)
     : m_me(other.m_me)
 {
+    Shiboken::GilState gil;
     Py_XINCREF(m_me);
 }
 
@@ -142,6 +148,7 @@ PyObjectWrapper::~PyObjectWrapper()
 
 void PyObjectWrapper::reset(PyObject *o)
 {
+    Shiboken::GilState gil;
     Py_XINCREF(o);
     Py_XDECREF(m_me);
     m_me = o;