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Proposal: Safe pointers #1043

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Merged
filmor merged 9 commits into from
Feb 26, 2020
Merged

Proposal: Safe pointers #1043

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4a84a1e
NewReference type and an example usage
lostmsu Feb 13, 2020
88944a2
BorrowedReference + example, that exposes dangerous pattern
lostmsu Feb 13, 2020
e1ba92c
actually, borrowed refrences can be copied
lostmsu Feb 13, 2020
2d11f82
make BorrowedReference readonly ref struct
lostmsu Feb 13, 2020
dbb3dc5
updated old project file
lostmsu Feb 13, 2020
7304b25
BorrowedReference.Pointer is a private readonly field
lostmsu Feb 13, 2020
2bc218c
drop C# 8.0 requirement
lostmsu Feb 13, 2020
2cf9fc3
renamed NewReference.ToPyObject to MoveToPyObject
lostmsu Feb 23, 2020
6ae63cd
added xmldoc comments to *Reference members
lostmsu Feb 23, 2020
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BorrowedReference + example, that exposes dangerous pattern
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@lostmsu
lostmsu committed Feb 13, 2020
commit 88944a2136e42e6cc4d38da3889d3c6ea2bffcd2
26 changes: 26 additions & 0 deletions src/runtime/BorrowedReference.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,26 @@
namespace Python.Runtime
{
using System;
[NonCopyable]
ref struct BorrowedReference
{
public IntPtr Pointer;
public bool IsNull => this.Pointer == IntPtr.Zero;

public PyObject ToPyObject()
{
if (this.IsNull) throw new NullReferenceException();

Runtime.XIncref(this.Pointer);
return new PyObject(this.Pointer);
}
}

static class BorrowedReferenceExtensions {
[Obsolete("Use overloads, that take BorrowedReference or NewReference")]
public static IntPtr DangerousGetAddress(this in BorrowedReference reference)
=> reference.IsNull() ? throw new NullReferenceException() : reference.Pointer;
public static bool IsNull(this in BorrowedReference reference)
=> reference.Pointer == IntPtr.Zero;
}
}
4 changes: 2 additions & 2 deletions src/runtime/assemblymanager.cs
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Expand Up @@ -145,7 +145,7 @@ internal static void UpdatePath()
probed.Clear();
for (var i = 0; i < count; i++)
{
IntPtr item = Runtime.PyList_GetItem(list, i);
BorrowedReference item = Runtime.PyList_GetItem(list, i);
string path = Runtime.GetManagedString(item);
if (path != null)
{
Expand Down Expand Up @@ -492,4 +492,4 @@ internal static Type[] GetTypes(Assembly a)
}
}
}
}
}
2 changes: 1 addition & 1 deletion src/runtime/methodbinder.cs
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Expand Up @@ -292,7 +292,7 @@ internal Binding Bind(IntPtr inst, IntPtr args, IntPtr kw, MethodBase info, Meth
for (int i = 0; i < pynkwargs; ++i)
{
var keyStr = Runtime.GetManagedString(Runtime.PyList_GetItem(keylist, i));
kwargDict[keyStr] = Runtime.PyList_GetItem(valueList, i);
kwargDict[keyStr] = Runtime.PyList_GetItem(valueList, i).DangerousGetAddress();
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@lostmsu lostmsu Feb 13, 2020

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This generates a compiler warning, that uncovers a potentially dangerous pattern, where kwargsDict may contain borrowed references.

}
Runtime.XDecref(keylist);
Runtime.XDecref(valueList);
Expand Down
6 changes: 4 additions & 2 deletions src/runtime/runtime.cs
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Expand Up @@ -1509,6 +1509,8 @@ internal static IntPtr PyUnicode_FromString(string s)
return PyUnicode_FromUnicode(s, s.Length);
}

internal static string GetManagedString(in BorrowedReference borrowedReference)
=> GetManagedString(borrowedReference.DangerousGetAddress());
/// <summary>
/// Function to access the internal PyUnicode/PyString object and
/// convert it to a managed string with the correct encoding.
Expand Down Expand Up @@ -1631,13 +1633,13 @@ internal static IntPtr PyList_New(long size)
[DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
internal static extern IntPtr PyList_AsTuple(IntPtr pointer);

internal static IntPtr PyList_GetItem(IntPtr pointer, long index)
internal static BorrowedReference PyList_GetItem(IntPtr pointer, long index)
{
return PyList_GetItem(pointer, new IntPtr(index));
}

[DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
private static extern IntPtr PyList_GetItem(IntPtr pointer, IntPtr index);
private static extern BorrowedReference PyList_GetItem(IntPtr pointer, IntPtr index);

internal static int PyList_SetItem(IntPtr pointer, long index, IntPtr value)
{
Expand Down