https://github.com/python/cpython/commit/f37602ad7d4b78f55d935be66f6373320fe... commit: f37602ad7d4b78f55d935be66f6373320fe0aee5 branch: main author: thexai <58434170+thexai@users.noreply.github.com> committer: chris-eibl <138194463+chris-eibl@users.noreply.github.com> date: 2026-06-30T22:35:44+02:00 summary: gh-152433: Windows: use GetFileSizeEx instead of GetFileSize for memory mapped files (#152383) files: A Misc/NEWS.d/next/Windows/2026-06-28-13-03-57.gh-issue-152433.jUXFwC.rst M Modules/mmapmodule.c diff --git a/Misc/NEWS.d/next/Windows/2026-06-28-13-03-57.gh-issue-152433.jUXFwC.rst b/Misc/NEWS.d/next/Windows/2026-06-28-13-03-57.gh-issue-152433.jUXFwC.rst new file mode 100644 index 00000000000000..348bfa4ee9c278 --- /dev/null +++ b/Misc/NEWS.d/next/Windows/2026-06-28-13-03-57.gh-issue-152433.jUXFwC.rst @@ -0,0 +1 @@ +Use the Windows API ``GetFileSizeEx()`` for memory mapped files, rather than the older ``GetFileSize()``. diff --git a/Modules/mmapmodule.c b/Modules/mmapmodule.c index 6fb04ba7bd47c6..f4f21b45f920a0 100644 --- a/Modules/mmapmodule.c +++ b/Modules/mmapmodule.c @@ -806,20 +806,12 @@ mmap_mmap_size_impl(mmap_object *self) #ifdef MS_WINDOWS if (self->file_handle != INVALID_HANDLE_VALUE) { - DWORD low,high; - long long size; - low = GetFileSize(self->file_handle, &high); - if (low == INVALID_FILE_SIZE) { - /* It might be that the function appears to have failed, - when indeed its size equals INVALID_FILE_SIZE */ - DWORD error = GetLastError(); - if (error != NO_ERROR) - return PyErr_SetFromWindowsErr(error); + LARGE_INTEGER size; + if (!GetFileSizeEx(self->file_handle, &size)) { + DWORD error = GetLastError(); + return PyErr_SetFromWindowsErr(error); } - if (!high && low < LONG_MAX) - return PyLong_FromLong((long)low); - size = (((long long)high)<<32) + low; - return PyLong_FromLongLong(size); + return PyLong_FromLongLong(size.QuadPart); } #endif /* MS_WINDOWS */ @@ -2127,18 +2119,14 @@ new_mmap_object(PyTypeObject *type, PyObject *args, PyObject *kwdict) m_obj->file_handle = fh; } if (!map_size) { - DWORD low,high; - low = GetFileSize(fh, &high); - /* low might just happen to have the value INVALID_FILE_SIZE; - so we need to check the last error also. */ - if (low == INVALID_FILE_SIZE && - (dwErr = GetLastError()) != NO_ERROR) + LARGE_INTEGER li; + if (!GetFileSizeEx(fh, &li)) { + dwErr = GetLastError(); Py_DECREF(m_obj); return PyErr_SetFromWindowsErr(dwErr); } - - size = (((long long) high) << 32) + low; + size = li.QuadPart; if (size == 0) { PyErr_SetString(PyExc_ValueError, "cannot mmap an empty file");