https://github.com/python/cpython/commit/f37602ad7d4b78f55d935be66f6373320fe0aee5
commit: f37602ad7d4b78f55d935be66f6373320fe0aee5
branch: main
author: thexai <[email protected]>
committer: chris-eibl <[email protected]>
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");
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