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[3.11] bpo-40882: Fix a memory leak in SharedMemory on Windows (GH-20684
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) (#99973)

bpo-40882: Fix a memory leak in SharedMemory on Windows (GH-20684)

In multiprocessing.shared_memory.SharedMemory(), the temporary view
returned by MapViewOfFile() should be unmapped when it is no longer
needed.

(cherry picked from commit 85c128e)

Co-authored-by: Zackery Spytz <zspytz@gmail.com>
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lukegarland and ZackerySpytz authored Dec 5, 2022
1 parent 7f2bcc7 commit 374b0a2
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Showing 4 changed files with 58 additions and 2 deletions.
5 changes: 4 additions & 1 deletion Lib/multiprocessing/shared_memory.py
Original file line number Diff line number Diff line change
Expand Up @@ -173,7 +173,10 @@ def __init__(self, name=None, create=False, size=0):
)
finally:
_winapi.CloseHandle(h_map)
size = _winapi.VirtualQuerySize(p_buf)
try:
size = _winapi.VirtualQuerySize(p_buf)
finally:
_winapi.UnmapViewOfFile(p_buf)
self._mmap = mmap.mmap(-1, size, tagname=name)

self._size = size
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix a memory leak in :class:`multiprocessing.shared_memory.SharedMemory` on
Windows.
25 changes: 25 additions & 0 deletions Modules/_winapi.c
Original file line number Diff line number Diff line change
Expand Up @@ -1402,6 +1402,30 @@ _winapi_MapViewOfFile_impl(PyObject *module, HANDLE file_map,
return address;
}

/*[clinic input]
_winapi.UnmapViewOfFile
address: LPCVOID
/
[clinic start generated code]*/

static PyObject *
_winapi_UnmapViewOfFile_impl(PyObject *module, LPCVOID address)
/*[clinic end generated code: output=4f7e18ac75d19744 input=8c4b6119ad9288a3]*/
{
BOOL success;

Py_BEGIN_ALLOW_THREADS
success = UnmapViewOfFile(address);
Py_END_ALLOW_THREADS

if (!success) {
return PyErr_SetFromWindowsErr(0);
}

Py_RETURN_NONE;
}

/*[clinic input]
_winapi.OpenFileMapping -> HANDLE
Expand Down Expand Up @@ -2095,6 +2119,7 @@ static PyMethodDef winapi_functions[] = {
_WINAPI_READFILE_METHODDEF
_WINAPI_SETNAMEDPIPEHANDLESTATE_METHODDEF
_WINAPI_TERMINATEPROCESS_METHODDEF
_WINAPI_UNMAPVIEWOFFILE_METHODDEF
_WINAPI_VIRTUALQUERYSIZE_METHODDEF
_WINAPI_WAITNAMEDPIPE_METHODDEF
_WINAPI_WAITFORMULTIPLEOBJECTS_METHODDEF
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28 changes: 27 additions & 1 deletion Modules/clinic/_winapi.c.h

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