Fix limited API incompatibility with Python 3.7

When Python 3.7 appeared, the structure of pystate.h was changed,
substantially. Unfortunately this structure contains the trashcan
code, which is only available as a macro and not part of the limited API.

This code is normally not used by application programs.
It prevents crashes when chains of millions of objects are deallocated.
I disabled this for now when the limited API is active.

As soon as somebody complains about crashes, I will try to implement
it again in a safe way, but I am not sure if it is worth it in the first place.

Task-number: PYSIDE-737
Change-Id: Id0daf391448ddcb9df3d299f859ef024714fa736
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

3 files changed, 8 insertions, 77 deletions

diff --git a/sources/shiboken2/libshiboken/basewrapper.cpp b/sources/shiboken2/libshiboken/basewrapper.cpp
index ae6b2a68a..122e60e41 100644
--- a/sources/shiboken2/libshiboken/basewrapper.cpp
+++ b/sources/shiboken2/libshiboken/basewrapper.cpp
@@ -259,7 +259,9 @@ void SbkObjectTypeDealloc(PyObject* pyObj)
     PyTypeObject *type = reinterpret_cast<PyTypeObject*>(pyObj);
 
     PyObject_GC_UnTrack(pyObj);
+#ifndef Py_LIMITED_API
     Py_TRASHCAN_SAFE_BEGIN(pyObj);
+#endif
     if (sotp) {
         if (sotp->user_data && sotp->d_func) {
             sotp->d_func(sotp->user_data);
@@ -272,7 +274,9 @@ void SbkObjectTypeDealloc(PyObject* pyObj)
         delete sotp;
         sotp = nullptr;
     }
+#ifndef Py_LIMITED_API
     Py_TRASHCAN_SAFE_END(pyObj);
+#endif
 }
 
 PyObject* SbkObjectTypeTpNew(PyTypeObject* metatype, PyObject* args, PyObject* kwds)
diff --git a/sources/shiboken2/libshiboken/pep384impl.h b/sources/shiboken2/libshiboken/pep384impl.h
index d5b0c7654..8f14c853a 100644
--- a/sources/shiboken2/libshiboken/pep384impl.h
+++ b/sources/shiboken2/libshiboken/pep384impl.h
@@ -288,83 +288,6 @@ typedef struct _methoddescr PyMethodDescrObject;
 
 /*****************************************************************************
  *
- * RESOLVED: pystate.h
- *
- */
-
-/*
- * pystate provides the data structure that is needed for the trashcan
- * algorithm. Unfortunately, it is not included in the limited API.
- * We have two options:
- *
- *  (1) ignore trashcan and live without secured deeply nested structures,
- *  (2) maintain the structure ourselves and make sure it does not change.
- *
- * I have chosen the second option.
- *
- * When a new python version appears, you need to check compatibility of
- * the PyThreadState structure (pystate.h) and the trashcan macros at the
- * end of object.h .
- */
-
-#ifdef Py_LIMITED_API
-
-#define Py_TRASH_MIN_COMPATIBLE 0x03020400
-#define Py_TRASH_MAX_COMPATIBLE 0x0307FFFF
-
-#if PY_VERSION_HEX >= Py_TRASH_MIN_COMPATIBLE && \
-    PY_VERSION_HEX <= Py_TRASH_MAX_COMPATIBLE
-typedef int (*Py_tracefunc)(PyObject *, struct _frame *, int, PyObject *);
-
-// This structure has the trashcan variables since Python 3.2.4.
-// We renamed all but the trashcan fields to make sure that we don't use
-// anything else somewhere.
-
-typedef struct _ts {
-    struct _ts *Pep_prev;
-    struct _ts *Pep_next;
-    PyInterpreterState *Pep_interp;
-
-    struct _frame *Pep_frame;
-    int Pep_recursion_depth;
-    char Pep_overflowed;
-    char Pep_recursion_critical;
-
-    int Pep_tracing;
-    int Pep_use_tracing;
-
-    Py_tracefunc Pep_c_profilefunc;
-    Py_tracefunc Pep_c_tracefunc;
-    PyObject *Pep_c_profileobj;
-    PyObject *Pep_c_traceobj;
-
-    PyObject *Pep_curexc_type;
-    PyObject *Pep_curexc_value;
-    PyObject *Pep_curexc_traceback;
-
-    PyObject *Pep_exc_type;
-    PyObject *Pep_exc_value;
-    PyObject *Pep_exc_traceback;
-
-    PyObject *Pep_dict;
-
-    int Pep_gilstate_counter;
-
-    PyObject *Pep_async_exc;
-    long Pep_thread_id;
-    // These two variables only are of interest to us.
-    int trash_delete_nesting;
-    PyObject *trash_delete_later;
-    // Here we cut away the rest of the reduced structure.
-} PyThreadState;
-#else
-#error *** Please check compatibility of the trashcan code, see Pep.h ***
-#endif
-
-#endif // Py_LIMITED_API
-
-/*****************************************************************************
- *
  * RESOLVED: pythonrun.h
  *
  */
diff --git a/sources/shiboken2/libshiboken/sbkenum.cpp b/sources/shiboken2/libshiboken/sbkenum.cpp
index 5f753293c..119591215 100644
--- a/sources/shiboken2/libshiboken/sbkenum.cpp
+++ b/sources/shiboken2/libshiboken/sbkenum.cpp
@@ -312,11 +312,15 @@ void SbkEnumTypeDealloc(PyObject* pyObj)
     SbkEnumType* sbkType = reinterpret_cast<SbkEnumType*>(pyObj);
 
     PyObject_GC_UnTrack(pyObj);
+#ifndef Py_LIMITED_API
     Py_TRASHCAN_SAFE_BEGIN(pyObj);
+#endif
     if (PepType_SETP(sbkType)->converter) {
         Shiboken::Conversions::deleteConverter(PepType_SETP(sbkType)->converter);
     }
+#ifndef Py_LIMITED_API
     Py_TRASHCAN_SAFE_END(pyObj);
+#endif
 }
 
 PyObject* SbkEnumTypeTpNew(PyTypeObject* metatype, PyObject* args, PyObject* kwds)