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using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
namespace Python.Runtime
{
public class Finalizer
{
public class CollectArgs : EventArgs
{
public int ObjectCount { get; set; }
}
public class ErrorArgs : EventArgs
{
public bool Handled { get; set; }
public Exception Error { get; set; }
}
public static readonly Finalizer Instance = new Finalizer();
public event EventHandler<CollectArgs> BeforeCollect;
public event EventHandler<ErrorArgs> ErrorHandler;
const int DefaultThreshold = 200;
[DefaultValue(DefaultThreshold)]
public int Threshold { get; set; } = DefaultThreshold;
bool started;
[DefaultValue(true)]
public bool Enable { get; set; } = true;
private ConcurrentQueue<PendingFinalization> _objQueue = new ();
private int _throttled;
#region FINALIZER_CHECK
#if FINALIZER_CHECK
private readonly object _queueLock = new object();
internal bool RefCountValidationEnabled { get; set; } = true;
#else
internal bool RefCountValidationEnabled { get; set; } = false;
#endif
// Keep these declarations for compat even no FINALIZER_CHECK
internal class IncorrectFinalizeArgs : EventArgs
{
public IntPtr Handle { get; internal set; }
public ICollection<IntPtr> ImpactedObjects { get; internal set; }
}
internal class IncorrectRefCountException : Exception
{
public IntPtr PyPtr { get; internal set; }
private string _message;
public override string Message => _message;
internal IncorrectRefCountException(IntPtr ptr)
{
PyPtr = ptr;
IntPtr pyname = Runtime.PyObject_Str(PyPtr);
string name = Runtime.GetManagedString(pyname);
Runtime.XDecref(pyname);
_message = $"<{name}> may has a incorrect ref count";
}
}
internal delegate bool IncorrectRefCntHandler(object sender, IncorrectFinalizeArgs e);
#pragma warning disable 414
internal event IncorrectRefCntHandler IncorrectRefCntResolver = null;
#pragma warning restore 414
internal bool ThrowIfUnhandleIncorrectRefCount { get; set; } = true;
#endregion
public void Collect() => this.DisposeAll();
internal void ThrottledCollect()
{
if (!started) throw new InvalidOperationException($"{nameof(PythonEngine)} is not initialized");
_throttled = unchecked(this._throttled + 1);
if (!Enable || _throttled < Threshold) return;
_throttled = 0;
this.Collect();
}
internal List<IntPtr> GetCollectedObjects()
{
return _objQueue.Select(o => o.PyObj).ToList();
}
internal void AddFinalizedObject(ref IntPtr obj, int run)
{
Debug.Assert(obj != IntPtr.Zero);
if (!Enable)
{
return;
}
#if FINALIZER_CHECK
lock (_queueLock)
#endif
{
this._objQueue.Enqueue(new PendingFinalization { PyObj = obj, RuntimeRun = run });
}
obj = IntPtr.Zero;
}
internal static void Initialize()
{
Instance.started = true;
}
internal static void Shutdown()
{
Instance.DisposeAll();
Instance.started = false;
}
private void DisposeAll()
{
BeforeCollect?.Invoke(this, new CollectArgs()
{
ObjectCount = _objQueue.Count
});
#if FINALIZER_CHECK
lock (_queueLock)
#endif
{
#if FINALIZER_CHECK
ValidateRefCount();
#endif
Runtime.PyErr_Fetch(out var errType, out var errVal, out var traceback);
int run = Runtime.GetRun();
try
{
while (!_objQueue.IsEmpty)
{
if (!_objQueue.TryDequeue(out var obj))
continue;
if (obj.RuntimeRun != run)
{
HandleFinalizationException(obj.PyObj, new RuntimeShutdownException(obj.PyObj));
continue;
}
Runtime.XDecref(obj.PyObj);
try
{
Runtime.CheckExceptionOccurred();
}
catch (Exception e)
{
HandleFinalizationException(obj.PyObj, e);
}
}
}
finally
{
// Python requires finalizers to preserve exception:
// https://docs.python.org/3/extending/newtypes.html#finalization-and-de-allocation
Runtime.PyErr_Restore(errType.StealNullable(), errVal.StealNullable(), traceback.StealNullable());
}
}
}
void HandleFinalizationException(IntPtr obj, Exception cause)
{
var errorArgs = new ErrorArgs
{
Error = cause,
};
ErrorHandler?.Invoke(this, errorArgs);
if (!errorArgs.Handled)
{
throw new FinalizationException(
"Python object finalization failed",
disposable: obj, innerException: cause);
}
}
#if FINALIZER_CHECK
private void ValidateRefCount()
{
if (!RefCountValidationEnabled)
{
return;
}
var counter = new Dictionary<IntPtr, long>();
var holdRefs = new Dictionary<IntPtr, long>();
var indexer = new Dictionary<IntPtr, List<IntPtr>>();
foreach (var obj in _objQueue)
{
var handle = obj;
if (!counter.ContainsKey(handle))
{
counter[handle] = 0;
}
counter[handle]++;
if (!holdRefs.ContainsKey(handle))
{
holdRefs[handle] = Runtime.Refcount(handle);
}
List<IntPtr> objs;
if (!indexer.TryGetValue(handle, out objs))
{
objs = new List<IntPtr>();
indexer.Add(handle, objs);
}
objs.Add(obj);
}
foreach (var pair in counter)
{
IntPtr handle = pair.Key;
long cnt = pair.Value;
// Tracked handle's ref count is larger than the object's holds
// it may take an unspecified behaviour if it decref in Dispose
if (cnt > holdRefs[handle])
{
var args = new IncorrectFinalizeArgs()
{
Handle = handle,
ImpactedObjects = indexer[handle]
};
bool handled = false;
if (IncorrectRefCntResolver != null)
{
var funcList = IncorrectRefCntResolver.GetInvocationList();
foreach (IncorrectRefCntHandler func in funcList)
{
if (func(this, args))
{
handled = true;
break;
}
}
}
if (!handled && ThrowIfUnhandleIncorrectRefCount)
{
throw new IncorrectRefCountException(handle);
}
}
// Make sure no other references for PyObjects after this method
indexer[handle].Clear();
}
indexer.Clear();
}
#endif
}
struct PendingFinalization
{
public IntPtr PyObj;
public int RuntimeRun;
}
public class FinalizationException : Exception
{
public IntPtr Handle { get; }
/// <summary>
/// Gets the object, whose finalization failed.
///
/// <para>If this function crashes, you can also try <see cref="DebugGetObject"/>,
/// which does not attempt to increase the object reference count.</para>
/// </summary>
public PyObject GetObject() => new(new BorrowedReference(this.Handle));
/// <summary>
/// Gets the object, whose finalization failed without incrementing
/// its reference count. This should only ever be called during debugging.
/// When the result is disposed or finalized, the program will crash.
/// </summary>
public PyObject DebugGetObject() => new(this.Handle);
public FinalizationException(string message, IntPtr disposable, Exception innerException)
: base(message, innerException)
{
if (disposable == IntPtr.Zero) throw new ArgumentNullException(nameof(disposable));
this.Handle = disposable;
}
protected FinalizationException(string message, IntPtr disposable)
: base(message)
{
if (disposable == IntPtr.Zero) throw new ArgumentNullException(nameof(disposable));
this.Handle = disposable;
}
}
public class RuntimeShutdownException : FinalizationException
{
public RuntimeShutdownException(IntPtr disposable)
: base("Python runtime was shut down after this object was created." +
" It is an error to attempt to dispose or to continue using it even after restarting the runtime.", disposable)
{
}
}
}