lxml on Windows crashes with large file

[Charlie_X]

Using xmlfile to write a large file and hitting problems on Windows. I guess there's a memory problem. This is using lxml 3.7.2. The source file can be got from https://bitbucket.org/openpyxl/openpyxl/issues/494

Python : sys.version_info(major=3, minor=4, micro=4, releaselevel='
final', serial=0)
lxml.etree : (3, 7, 2, 0)
libxml used : (2, 9, 4)
libxml compiled : (2, 9, 4)
libxslt used : (1, 1, 29)
libxslt compiled : (1, 1, 29)

Traceback:

Python 3.4.4 (v3.4.4:737efcadf5a6, Dec 20 2015, 19:28:18) [MSC v.1600 32 bit (In
tel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from openpyxl import load_workbook
>>> wb = load_workbook(r"Z:\Projects\openpyxl\Issues\bug494.xlsx")
>>> wb.save("bug494-win.xlsx")
Traceback (most recent call last):
  File "C:\openpyxl\openpyxl\writer\etree_worksheet.py", line 56, in write_row
    el = write_cell(xf, worksheet, cell, cell.has_style)
  File "C:\openpyxl\openpyxl\writer\etree_worksheet.py", line 118, in lxml_write
_cell
    with xf.element('c', attributes):
  File "src\lxml\serializer.pxi", line 1228, in lxml.etree._FileWriterElement.__
enter__ (src\lxml\lxml.etree.c:146096)
  File "src\lxml\serializer.pxi", line 1064, in lxml.etree._IncrementalFileWrite
r._write_start_element (src\lxml\lxml.etree.c:143370)
  File "src\lxml\serializer.pxi", line 1213, in lxml.etree._IncrementalFileWrite
r._handle_error (src\lxml\lxml.etree.c:145890)
  File "src\lxml\lxml.etree.pyx", line 324, in lxml.etree._ExceptionContext._rai
se_if_stored (src\lxml\lxml.etree.c:12064)
  File "src\lxml\serializer.pxi", line 643, in lxml.etree._FilelikeWriter.write
(src\lxml\lxml.etree.c:137506)
MemoryError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\openpyxl\openpyxl\writer\etree_worksheet.py", line 36, in write_rows
    write_row(xf, worksheet, row, row_idx, max_column)
  File "C:\openpyxl\openpyxl\writer\etree_worksheet.py", line 56, in write_row
    el = write_cell(xf, worksheet, cell, cell.has_style)
  File "src\lxml\serializer.pxi", line 1231, in lxml.etree._FileWriterElement.__
exit__ (src\lxml\lxml.etree.c:146212)
  File "src\lxml\serializer.pxi", line 1107, in lxml.etree._IncrementalFileWrite
r._write_end_element (src\lxml\lxml.etree.c:144205)
  File "src\lxml\serializer.pxi", line 1214, in lxml.etree._IncrementalFileWrite
r._handle_error (src\lxml\lxml.etree.c:145908)
  File "src\lxml\serializer.pxi", line 195, in lxml.etree._raiseSerialisationErr
or (src\lxml\lxml.etree.c:133135)
lxml.etree.SerialisationError: IO_WRITE

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\openpyxl\openpyxl\writer\worksheet.py", line 108, in write_worksheet
    write_rows(xf, ws)
  File "C:\openpyxl\openpyxl\writer\etree_worksheet.py", line 36, in write_rows
    write_row(xf, worksheet, row, row_idx, max_column)
  File "src\lxml\serializer.pxi", line 1231, in lxml.etree._FileWriterElement.__
exit__ (src\lxml\lxml.etree.c:146212)
  File "src\lxml\serializer.pxi", line 1107, in lxml.etree._IncrementalFileWrite
r._write_end_element (src\lxml\lxml.etree.c:144205)
  File "src\lxml\serializer.pxi", line 1214, in lxml.etree._IncrementalFileWrite
r._handle_error (src\lxml\lxml.etree.c:145908)
  File "src\lxml\serializer.pxi", line 195, in lxml.etree._raiseSerialisationErr
or (src\lxml\lxml.etree.c:133135)
lxml.etree.SerialisationError: IO_WRITE

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\openpyxl\openpyxl\workbook\workbook.py", line 342, in save
    save_workbook(self, filename)
  File "C:\openpyxl\openpyxl\writer\excel.py", line 268, in save_workbook
    writer.save(filename)
  File "C:\openpyxl\openpyxl\writer\excel.py", line 250, in save
    self.write_data()
  File "C:\openpyxl\openpyxl\writer\excel.py", line 81, in write_data
    self._write_worksheets()
  File "C:\openpyxl\openpyxl\writer\excel.py", line 199, in _write_worksheets
    xml = ws._write()
  File "C:\openpyxl\openpyxl\worksheet\worksheet.py", line 870, in _write
    return write_worksheet(self)
  File "C:\openpyxl\openpyxl\writer\worksheet.py", line 177, in write_worksheet
    xf.write(tables.to_tree())
  File "src\lxml\serializer.pxi", line 1231, in lxml.etree._FileWriterElement.__
exit__ (src\lxml\lxml.etree.c:146212)
  File "src\lxml\serializer.pxi", line 1107, in lxml.etree._IncrementalFileWrite
r._write_end_element (src\lxml\lxml.etree.c:144205)
  File "src\lxml\serializer.pxi", line 1214, in lxml.etree._IncrementalFileWrite
r._handle_error (src\lxml\lxml.etree.c:145908)
  File "src\lxml\serializer.pxi", line 195, in lxml.etree._raiseSerialisationErr
or (src\lxml\lxml.etree.c:133135)
lxml.etree.SerialisationError: IO_WRITE

[scoder (scoder)]

Sorry for looking at this so late, but this probably isn't writing to a file on disk directly, right? Is this writing to an in-memory file-like object in some way?