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gettext.GNUTranslations raises struct.error instead of OSError on a malformed .mo file #153605
Description
Bug report
Bug description:
gettext.GNUTranslations parses a .mo file by unpacking its header and seek
tables with struct.unpack, but never checks the file is long enough. A
truncated file (shorter than the 20-byte header) or one whose seek tables point
past the end raises a raw struct.error instead of the OSError the module
already raises for other malformed input (a bad magic number, a bad version, or
an out-of-range string offset). The documentation states OSError is raised for
problems while reading the file, so the struct.error is an undocumented leak.
import gettext, io
gettext.GNUTranslations(io.BytesIO(b"\xde\x12\x04\x95")) # raises struct.error
CPython versions tested on:
3.13, 3.14, 3.15, 3.16
Operating systems tested on:
macOS
Activity
serhiy-storchaka commentedon Aug 17, 2026
Since
OSErroris not specific togettext, other option -- simply document other exceptions.gh-153605: Fix `gettext.GNUTranslations` raising `struct.error` on a …
StanFromIreland commentedon Oct 25, 2026
That's also an option, but I think the error message may currently be confusing for users (it looks like a bug in
gettextrather than your catalogue!), so I merged a simplified patch.