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gh-144069: Fix memory leak in _dbm.open() on failure #144075

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gh-144069: Fix memory leak in _dbm.open() on failure #144075

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gh-144069: Fix memory leak in _dbm.open() on failure
VanshAgarwal24036 Jan 20, 2026
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VanshAgarwal24036 Jan 20, 2026
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4 changes: 4 additions & 0 deletions Lib/test/test_dbm.py
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Original file line number Diff line number Diff line change
Expand Up @@ -244,6 +244,10 @@ def setUp(self):
self.addCleanup(cleaunup_test_dir)
setup_test_dir()

def test_open_nonexistent_directory(self):
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@picnixz picnixz Jan 20, 2026

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Can you put the test closer to other open()-tests? please be mindful of the quality of the PRs you submit.

missing_dir = os.path.join(dirname + "_does_not_exist", "test.db")
with self.assertRaises(OSError):
dbm.open(missing_dir, "c")

class WhichDBTestCase(unittest.TestCase):
def test_whichdb(self):
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/C_API/2026-01-20-20-17-16.gh-issue-144069.IE5fug.rst
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@@ -0,0 +1,2 @@
Fix a memory leak in :func:`dbm.open` when database creation fails, such as
when the target directory does not exist.
7 changes: 6 additions & 1 deletion Modules/_dbmmodule.c
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Expand Up @@ -85,11 +85,16 @@ newdbmobject(_dbm_state *state, const char *file, int flags, int mode)
}
dp->di_size = -1;
dp->flags = flags;
dp->di_dbm = NULL;
PyObject_GC_Track(dp);

/* See issue #19296 */
if ( (dp->di_dbm = dbm_open((char *)file, flags, mode)) == 0 ) {
if ( (dp->di_dbm = dbm_open((char *)file, flags, mode)) == NULL ) {
PyErr_SetFromErrnoWithFilename(state->dbm_error, file);
if (dp->di_dbm != NULL) {
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@serhiy-storchaka serhiy-storchaka Jan 20, 2026

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Wait, we just tested that dp->di_dbm == NULL.

dbm_close(dp->di_dbm);
dp->di_dbm = NULL;
}
Comment on lines +94 to +97
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@picnixz picnixz Jan 20, 2026

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No need for that, you can leave it to dealloc. In addition this code path will never be taken as di_dbm will be NULL... this is exactly your if test.

However add dp->di_dbm = NULL in dbm_dealloc() to prevent double frees.

Py_DECREF(dp);
return NULL;
}
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