MemoryRegulator.cxx

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// Bindings
#include "CPyCppyy.h"
#include "MemoryRegulator.h"
#include "CPPInstance.h"
#include "ProxyWrappers.h"
 
// Standard
#include <assert.h>
#include <string.h>
#include <iostream>
 
 
//= pseudo-None type for masking out objects on the python side ===============
static PyTypeObject CPyCppyy_NoneType;
 
//-----------------------------------------------------------------------------
static Py_ssize_t AlwaysNullLength(PyObject*)
{
    return 0;
}
 
//-----------------------------------------------------------------------------
static PyMappingMethods CPyCppyy_NoneType_mapping = {
    AlwaysNullLength,
    (binaryfunc)              0,
    (objobjargproc)           0
};
 
// silence warning about some cast operations
#if defined(__GNUC__) && (__GNUC__ >= 5 || (__GNUC__ >= 4 && ((__GNUC_MINOR__ == 2 && __GNUC_PATCHLEVEL__ >= 1) || (__GNUC_MINOR__ >= 3)))) && !__INTEL_COMPILER
#pragma GCC diagnostic ignored "-Wstrict-aliasing"
#endif
 
 
//-----------------------------------------------------------------------------
namespace {
 
// Py_SET_REFCNT was only introduced in Python 3.9
#if PY_VERSION_HEX < 0x03090000
inline void Py_SET_REFCNT(PyObject *ob, Py_ssize_t refcnt) {
    assert(refcnt >= 0);
#if SIZEOF_VOID_P > 4
    ob->ob_refcnt = (PY_UINT32_T)refcnt;
#else
    ob->ob_refcnt = refcnt;
#endif
}
#endif
 
struct InitCPyCppyy_NoneType_t {
    InitCPyCppyy_NoneType_t() {
    // create a CPyCppyy NoneType (for references that went dodo) from NoneType
        memset(&CPyCppyy_NoneType, 0, sizeof(CPyCppyy_NoneType));
 
        ((PyObject&)CPyCppyy_NoneType).ob_type    = &PyType_Type;
        Py_SET_REFCNT((PyObject*)&CPyCppyy_NoneType, 1);
        ((PyVarObject&)CPyCppyy_NoneType).ob_size = 0;
 
        CPyCppyy_NoneType.tp_name        = const_cast<char*>("CPyCppyy_NoneType");
        CPyCppyy_NoneType.tp_flags       = Py_TPFLAGS_HAVE_RICHCOMPARE;
 
        CPyCppyy_NoneType.tp_traverse    = (traverseproc)0;
        CPyCppyy_NoneType.tp_clear       = (inquiry)0;
        CPyCppyy_NoneType.tp_dealloc     = (destructor)&InitCPyCppyy_NoneType_t::DeAlloc;
        CPyCppyy_NoneType.tp_repr        = Py_TYPE(Py_None)->tp_repr;
        CPyCppyy_NoneType.tp_richcompare = (richcmpfunc)&InitCPyCppyy_NoneType_t::RichCompare;
#if PY_VERSION_HEX < 0x03000000
    // tp_compare has become tp_reserved (place holder only) in p3
        CPyCppyy_NoneType.tp_compare     = (cmpfunc)&InitCPyCppyy_NoneType_t::Compare;
#endif
        CPyCppyy_NoneType.tp_hash        = (hashfunc)&InitCPyCppyy_NoneType_t::PtrHash;
 
        CPyCppyy_NoneType.tp_as_mapping  = &CPyCppyy_NoneType_mapping;
 
        PyType_Ready(&CPyCppyy_NoneType);
    }
 
    static void DeAlloc(PyObject* pyobj) { Py_TYPE(pyobj)->tp_free(pyobj); }
    static int PtrHash(PyObject* pyobj) { return (int)ptrdiff_t(pyobj); }
 
    static PyObject* RichCompare(PyObject*, PyObject* other, int opid) {
        return PyObject_RichCompare(other, Py_None, opid);
    }
 
    static int Compare(PyObject*, PyObject* other) {
#if PY_VERSION_HEX < 0x03000000
        return PyObject_Compare(other, Py_None);
#else
    // TODO the following isn't correct as it doesn't order, but will do for now ...
        return !PyObject_RichCompareBool(other, Py_None, Py_EQ);
#endif
    }
};
 
} // unnamed namespace
 
// Memory regulation hooks
CPyCppyy::MemHook_t CPyCppyy::MemoryRegulator::registerHook   = nullptr;
CPyCppyy::MemHook_t CPyCppyy::MemoryRegulator::unregisterHook = nullptr;
 
 
//- ctor/dtor ----------------------------------------------------------------
CPyCppyy::MemoryRegulator::MemoryRegulator()
{
// setup NoneType for referencing and create weakref cache
    static InitCPyCppyy_NoneType_t initCPyCppyy_NoneType;
}
 
 
//- public members -----------------------------------------------------------
bool CPyCppyy::MemoryRegulator::RecursiveRemove(
    Cppyy::TCppObject_t cppobj, Cppyy::TCppType_t klass)
{
// if registered by the framework, called whenever a cppobj gets destroyed
    if (!cppobj)
        return false;
 
    PyObject* pyscope = GetScopeProxy(klass);
    if (!CPPScope_Check(pyscope)) {
        Py_XDECREF(pyscope);
        return false;
    }
 
    CppToPyMap_t* cppobjs = ((CPPClass*)pyscope)->fImp.fCppObjects;
    if (!cppobjs) {       // table may have been deleted on shutdown
        Py_DECREF(pyscope);
        return false;
    }
 
// see whether we're tracking this object
    CppToPyMap_t::iterator ppo = cppobjs->find(cppobj);
 
    if (ppo != cppobjs->end()) {
    // get the tracked object
        CPPInstance* pyobj = (CPPInstance*)ppo->second;
 
    // erase the object from tracking
        pyobj->fFlags &= ~CPPInstance::kIsRegulated;
        cppobjs->erase(ppo);
 
    // nullify the object
        if (!CPyCppyy_NoneType.tp_traverse) {
        // take a reference as we're copying its function pointers
            Py_INCREF(Py_TYPE(pyobj));
 
        // all object that arrive here are expected to be of the same type ("instance")
            CPyCppyy_NoneType.tp_traverse   = Py_TYPE(pyobj)->tp_traverse;
            CPyCppyy_NoneType.tp_clear      = Py_TYPE(pyobj)->tp_clear;
            CPyCppyy_NoneType.tp_free       = Py_TYPE(pyobj)->tp_free;
            CPyCppyy_NoneType.tp_flags     |= Py_TYPE(pyobj)->tp_flags;
        } else if (CPyCppyy_NoneType.tp_traverse != Py_TYPE(pyobj)->tp_traverse) {
        // TODO: SystemError?
            std::cerr << "in CPyCppyy::MemoryRegulater, unexpected object of type: "
                      << Py_TYPE(pyobj)->tp_name << std::endl;
 
        // drop object and leave before too much damage is done
            Py_DECREF(pyscope);
            return false;
        }
 
    // notify any other weak referents by playing dead
        Py_ssize_t refcnt = Py_REFCNT((PyObject*)pyobj);
        Py_SET_REFCNT((PyObject*)pyobj, 0);
        PyObject_ClearWeakRefs((PyObject*)pyobj);
        Py_SET_REFCNT((PyObject*)pyobj, refcnt);
 
    // cleanup object internals
        pyobj->CppOwns();              // held object is out of scope now anyway
        op_dealloc_nofree(pyobj);      // normal object cleanup, while keeping memory
 
    // reset type object
        Py_INCREF((PyObject*)(void*)&CPyCppyy_NoneType);
        Py_DECREF(Py_TYPE(pyobj));
        ((PyObject*)pyobj)->ob_type = &CPyCppyy_NoneType;
 
        Py_DECREF(pyscope);
        return true;
    }
 
// unregulated cppobj
    Py_DECREF(pyscope);
    return false;
}
 
//-----------------------------------------------------------------------------
bool CPyCppyy::MemoryRegulator::RegisterPyObject(
    CPPInstance* pyobj, Cppyy::TCppObject_t cppobj)
{
// start tracking <cppobj> proxied by <pyobj>
    if (!(pyobj && cppobj))
        return false;
 
    if (registerHook) {
        auto res = registerHook(cppobj, pyobj->ObjectIsA(false));
        if (!res.second) return res.first;
    }
 
    CppToPyMap_t* cppobjs = ((CPPClass*)Py_TYPE(pyobj))->fImp.fCppObjects;
    if (!cppobjs)
        return false;
 
// if an address was already associated with a different object, then stop following
// the old and force insert the new proxy for following
    const auto& res = cppobjs->insert(std::make_pair(cppobj, (PyObject*)pyobj));
    if (!res.second) {
        ((CPPInstance*)res.first->second)->fFlags &= ~CPPInstance::kIsRegulated;
        (*cppobjs)[cppobj] = (PyObject*)pyobj;
    }
 
    pyobj->fFlags |= CPPInstance::kIsRegulated;
    return true;
}
 
//-----------------------------------------------------------------------------
bool CPyCppyy::MemoryRegulator::UnregisterPyObject(CPPInstance* pyobj, PyObject* pyclass)
{
// called when the proxy is garbage collected or is about delete the C++ instance
    if (!(pyobj && pyclass))
        return false;
 
    Cppyy::TCppObject_t cppobj = pyobj->IsSmart() ? pyobj->GetObjectRaw() : pyobj->GetObject();
    if (!cppobj)
        return false;
 
    if (unregisterHook) {
        auto res = unregisterHook(cppobj, ((CPPClass*)pyclass)->fCppType);
        if (!res.second) return res.first;
    }
 
    CppToPyMap_t* cppobjs = ((CPPClass*)pyclass)->fImp.fCppObjects;
    if (!cppobjs)
        return false;
 
// erase if tracked
    if (cppobjs->erase(cppobj)) {
        pyobj->fFlags &= ~CPPInstance::kIsRegulated;
        return true;
    }
 
    return false;
}
 
//-----------------------------------------------------------------------------
PyObject* CPyCppyy::MemoryRegulator::RetrievePyObject(Cppyy::TCppObject_t cppobj, PyObject* pyclass)
{
// lookup to see if a C++ address is already known, return old proxy if tracked
    if (!(cppobj && pyclass))
       return nullptr;
 
    CppToPyMap_t* cppobjs = ((CPPClass*)pyclass)->fImp.fCppObjects;
    if (!cppobjs)
        return nullptr;
 
    CppToPyMap_t::iterator ppo = cppobjs->find(cppobj);
    if (ppo != cppobjs->end()) {
        Py_INCREF(ppo->second);
        return ppo->second;
    }
 
    return nullptr;
}
 
 
//-----------------------------------------------------------------------------
void CPyCppyy::MemoryRegulator::SetRegisterHook(MemHook_t h) {
// Set custom register hook; called when a regulated object is to be tracked
    registerHook = h;
}
 
//-----------------------------------------------------------------------------
void CPyCppyy::MemoryRegulator::SetUnregisterHook(MemHook_t h) {
// Set custom unregister hook; called when a regulated object is to be untracked
    unregisterHook = h;
}