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_csv: DIALECT_GETATTR macro silently masks non-AttributeError exceptions #145966
Description
Bug report
Bug description:
In Modules/_csv.c, the DIALECT_GETATTR macro in dialect_new() calls PyErr_Clear() unconditionally when PyObject_GetAttrString() fails. This silently swallows all exception types including MemoryError, KeyboardInterrupt, RuntimeError, etc.
https://github.com/python/cpython/blob/main/Modules/_csv.c#L500-L507
#define DIALECT_GETATTR(v, n) \
do { \
if (v == NULL) { \
v = PyObject_GetAttrString(dialect, n); \
if (v == NULL) \
PyErr_Clear(); \
} \
} while (0)Only AttributeError (attribute not found) should be cleared. Other exceptions should propagate.
Reproducer
import csv, io
class MyDialect:
@property
def delimiter(self):
raise MemoryError("OOM")
quotechar = '"'
escapechar = None
doublequote = True
skipinitialspace = False
quoting = csv.QUOTE_MINIMAL
lineterminator = '\r\n'
strict = False
# Expected: raises MemoryError (was swallowed)
w = csv.writer(io.StringIO(), dialect=MyDialect())
w.writerow(['a', 'b'])
print(w.dialect.delimiter) # ',' All 8 dialect attributes are affected: delimiter, doublequote, escapechar, lineterminator, quotechar, quoting, skipinitialspace, strict.
Fix
#define DIALECT_GETATTR(v, n) \
do { \
if (v == NULL) { \
v = PyObject_GetAttrString(dialect, n); \
if (v == NULL) { \
if (PyErr_ExceptionMatches(PyExc_AttributeError)) \
PyErr_Clear(); \
else \
goto err; \
} \
} \
} while (0)CPython versions tested on:
CPython main branch
Operating systems tested on:
Linux
Activity
_csv:DIALECT_GETATTRmacro silently masks non-AttributeErrorexceptions #145967 as a duplicate of this issueStanFromIreland commentedon Mar 15, 2026
Do you want to write a patch?
raminfp commentedon Mar 15, 2026
@StanFromIreland Sure, done.
gh-145966: Fix _csv DIALECT_GETATTR macro silently masking non-Attrib…
encukou commentedon Mar 17, 2026
Thank you @raminfp for the fix, and @picnixz for the review!
This is a behaviour change; I think it's safer to skip backporting.
pythongh-145966: Fix _csv DIALECT_GETATTR macro silently masking non-…