shiboken: Fix dict access without GIL

In PYSIDE-803 we used an optimization that accessed
a dictionary without holding the GIL. This turned out to be not
correct, because PyDict_GetItem works with thread state
to maintain the global error variables.

PyDict_GetItemWithErrors can be used instead in a way that
allows releasing the GIL.

Task-number: PYSIDE-803
Task-number: PYSIDE-813
Change-Id: Ifb0cbb20c21ca9c8b3d099fff1db5410eb6824b4
Reviewed-by: Christian Tismer <tismer@stackless.com>

5 files changed, 71 insertions, 1 deletions

diff --git a/sources/pyside2/libpyside/signalmanager.cpp b/sources/pyside2/libpyside/signalmanager.cpp
index 01b347a3d..0fe0d0092 100644
--- a/sources/pyside2/libpyside/signalmanager.cpp
+++ b/sources/pyside2/libpyside/signalmanager.cpp
@@ -559,7 +559,10 @@ static MetaObjectBuilder *metaBuilderFromDict(PyObject *dict)
     if (!dict || !PyDict_Contains(dict, metaObjectAttr))
         return nullptr;
 
-    PyObject *pyBuilder = PyDict_GetItem(dict, metaObjectAttr);
+    // PYSIDE-813: The above assumption is not true in debug mode:
+    // PyDict_GetItem would touch PyThreadState_GET and the global error state.
+    // PyDict_GetItemWithError instead can work without GIL.
+    PyObject *pyBuilder = PyDict_GetItemWithError(dict, metaObjectAttr);
 #ifdef IS_PY3K
     return reinterpret_cast<MetaObjectBuilder *>(PyCapsule_GetPointer(pyBuilder, nullptr));
 #else
diff --git a/sources/pyside2/libpyside/signalmanager.h b/sources/pyside2/libpyside/signalmanager.h
index 229ddb91d..fe077bd1a 100644
--- a/sources/pyside2/libpyside/signalmanager.h
+++ b/sources/pyside2/libpyside/signalmanager.h
@@ -43,6 +43,7 @@
 #include "pysidemacros.h"
 
 #include <sbkpython.h>
+#include <shibokenmacros.h>
 
 #include <QtCore/QMetaMethod>
 
diff --git a/sources/shiboken2/libshiboken/pep384impl.cpp b/sources/shiboken2/libshiboken/pep384impl.cpp
index 9939bb410..9f51034f3 100644
--- a/sources/shiboken2/libshiboken/pep384impl.cpp
+++ b/sources/shiboken2/libshiboken/pep384impl.cpp
@@ -518,12 +518,57 @@ static PyTypeObject *getFunctionType(void)
     return reinterpret_cast<PyTypeObject *>(PepRun_GetResult(prog));
 }
 
+#endif // Py_LIMITED_API || Python 2
+
+/*****************************************************************************
+ *
+ * Support for dictobject.h
+ *
+ */
+
+// PYSIDE-803, PYSIDE-813: We need that GIL-free version from Python 2.7.12 .
+#if PY_VERSION_HEX < 0x03000000
+
+/* Variant of PyDict_GetItem() that doesn't suppress exceptions.
+   This returns NULL *with* an exception set if an exception occurred.
+   It returns NULL *without* an exception set if the key wasn't present.
+*/
+PyObject *
+PyDict_GetItemWithError(PyObject *op, PyObject *key)
+{
+    long hash;
+    PyDictObject *mp = reinterpret_cast<PyDictObject *>(op);
+    PyDictEntry *ep;
+    if (!PyDict_Check(op)) {
+        PyErr_BadInternalCall();
+        return nullptr;
+    }
+    if (!PyString_CheckExact(key) ||
+        (hash = (reinterpret_cast<PyStringObject *>(key))->ob_shash) == -1)
+    {
+        hash = PyObject_Hash(key);
+        if (hash == -1) {
+            return nullptr;
+        }
+    }
+
+    ep = (mp->ma_lookup)(mp, key, hash);
+    if (ep == nullptr) {
+        return nullptr;
+    }
+    return ep->me_value;
+}
+
+#endif
+
 /*****************************************************************************
  *
  * Extra support for signature.cpp
  *
  */
 
+#ifdef Py_LIMITED_API
+
 PyTypeObject *PepStaticMethod_TypePtr = nullptr;
 
 static PyTypeObject *
diff --git a/sources/shiboken2/libshiboken/pep384impl.h b/sources/shiboken2/libshiboken/pep384impl.h
index 676e6c82d..e735095e8 100644
--- a/sources/shiboken2/libshiboken/pep384impl.h
+++ b/sources/shiboken2/libshiboken/pep384impl.h
@@ -279,6 +279,17 @@ LIBSHIBOKEN_API char *_PepUnicode_AsString(PyObject *);
 
 /*****************************************************************************
  *
+ * RESOLVED: dictobject.h
+ *
+ * PYSIDE-803, PYSIDE-813: We need PyDict_GetItemWithError in order to
+ *                         avoid the GIL.
+ */
+#if PY_VERSION_HEX < 0x03000000
+LIBSHIBOKEN_API PyObject *PyDict_GetItemWithError(PyObject *mp, PyObject *key);
+#endif
+
+/*****************************************************************************
+ *
  * RESOLVED: methodobject.h
  *
  */
diff --git a/sources/shiboken2/libshiboken/pep384impl_doc.rst b/sources/shiboken2/libshiboken/pep384impl_doc.rst
index ac4b053a7..d8ebdbe70 100644
--- a/sources/shiboken2/libshiboken/pep384impl_doc.rst
+++ b/sources/shiboken2/libshiboken/pep384impl_doc.rst
@@ -106,6 +106,16 @@ listobject.h
 function calls.
 
 
+dictobject.h
+------------
+
+``PyDict_GetItem`` also exists in a ``PyDict_GetItemWithError`` version that does
+not suppress errors. This suppression has the side effect of touching global
+structures. This function exists in Python 2 only since Python 2.7.12 and has
+a different name. We simply implemented the function.
+Needed to avoid the GIL when accessing dictionaries.
+
+
 methodobject.h
 --------------