From c26e40bc54492685a11e24ccad72c00c9ce112e7 Mon Sep 17 00:00:00 2001 From: GruffElixir Date: Sat, 26 Sep 2026 16:18:13 +0530 Subject: [PATCH] [3.14] gh-158169: Clear `zlib.Decompress.unconsumed_tail` at end of stream (GH-158177) (cherry picked from commit 8122ff4818f418e8ae984cf6964215689b00808d) Co-authored-by: GruffElixir Co-authored-by: Stan Ulbrych --- Lib/test/test_zlib.py | 12 ++++++++++++ .../2026-09-25-22-15-54.gh-issue-158169.ZlibTail.rst | 2 ++ Modules/zlibmodule.c | 1 + 3 files changed, 15 insertions(+) create mode 100644 Misc/NEWS.d/next/Library/2026-09-25-22-15-54.gh-issue-158169.ZlibTail.rst diff --git a/Lib/test/test_zlib.py b/Lib/test/test_zlib.py index ed2eb0e05eb5327..9ef974b3e37d0f0 100644 --- a/Lib/test/test_zlib.py +++ b/Lib/test/test_zlib.py @@ -651,6 +651,18 @@ def test_decompress_unused_data(self): self.assertEqual(dco.unconsumed_tail, b'') self.assertEqual(dco.unused_data, remainder) + def test_decompress_unconsumed_tail_after_eof(self): + source = b'abcdefghijklmnopqrstuvwxyz' + remainder = b'0123456789' + dco = zlib.decompressobj() + data = dco.decompress(zlib.compress(source) + remainder, 1) + data += dco.decompress(dco.unconsumed_tail) + + self.assertTrue(dco.eof) + self.assertEqual(data, source) + self.assertEqual(dco.unconsumed_tail, b'') + self.assertEqual(dco.unused_data, remainder) + # issue27164 def test_decompress_raw_with_dictionary(self): zdict = b'abcdefghijklmnopqrstuvwxyz' diff --git a/Misc/NEWS.d/next/Library/2026-09-25-22-15-54.gh-issue-158169.ZlibTail.rst b/Misc/NEWS.d/next/Library/2026-09-25-22-15-54.gh-issue-158169.ZlibTail.rst new file mode 100644 index 000000000000000..7c965451c056a44 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-09-25-22-15-54.gh-issue-158169.ZlibTail.rst @@ -0,0 +1,2 @@ +Fix :attr:`zlib.Decompress.unconsumed_tail` duplicating +:attr:`~zlib.Decompress.unused_data` after end of stream when *max_length* was used. diff --git a/Modules/zlibmodule.c b/Modules/zlibmodule.c index 095e3e2b7dfacdf..fdd56534bca7edc 100644 --- a/Modules/zlibmodule.c +++ b/Modules/zlibmodule.c @@ -842,6 +842,7 @@ save_unconsumed_input(compobject *self, Py_buffer *data, int err) memcpy(PyBytes_AS_STRING(new_data) + old_size, self->zst.next_in, left_size); Py_SETREF(self->unused_data, new_data); + self->zst.next_in += left_size; self->zst.avail_in = 0; } }