From 9f9bdae0773166e8ed50dfdd1ed13cc4296819ce Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ha=C3=AFm=20Dimer?=
 <94395445+hdimer@users.noreply.github.com>
Date: Fri, 14 Aug 2026 00:48:27 -0700
Subject: [PATCH 1/2] Convert Packer's buf_size once (#726)

Fixes #723.
---
 msgpack/_packer.pyx |  2 +-
 test/test_pack.py   | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/msgpack/_packer.pyx b/msgpack/_packer.pyx
index 277239d8..e816c814 100644
--- a/msgpack/_packer.pyx
+++ b/msgpack/_packer.pyx
@@ -110,7 +110,7 @@ cdef class Packer:
     cdef bint autoreset
     cdef bint datetime
 
-    def __cinit__(self, buf_size=256*1024, **_kwargs):
+    def __cinit__(self, size_t buf_size=256*1024, **_kwargs):
         self.pk.buf = <char*> PyMem_Malloc(buf_size)
         if self.pk.buf == NULL:
             raise MemoryError("Unable to allocate internal buffer.")
diff --git a/test/test_pack.py b/test/test_pack.py
index 374d1549..f44bd557 100644
--- a/test/test_pack.py
+++ b/test/test_pack.py
@@ -179,3 +179,24 @@ def test_get_buffer():
 
     expected = packb([1, 2], use_bin_type=True)
     assert written == expected
+
+
+@pytest.mark.skipif(
+    Packer.__module__ == "msgpack.fallback",
+    reason="buf_size only allocates in the C extension",
+)
+def test_buf_size_is_converted_once():
+    # Asking twice let the allocation and the recorded capacity disagree,
+    # so the packer overflowed a buffer smaller than the size it recorded.
+    class Counting:
+        count = 0
+
+        def __int__(self):
+            self.count += 1
+            return 600
+
+        __index__ = __int__
+
+    buf_size = Counting()
+    Packer(buf_size=buf_size)
+    assert buf_size.count == 1

From 2e4be090f6a42e1ad19526ca6f6ee67f3476389a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ha=C3=AFm=20Dimer?=
 <94395445+hdimer@users.noreply.github.com>
Date: Sun, 16 Aug 2026 22:59:09 -0700
Subject: [PATCH 2/2] fix: translate RecursionError to StackError in fallback
 Unpacker.skip() (#727)

Finding #6 of #683.
---
 msgpack/fallback.py | 5 ++++-
 test/test_except.py | 5 +++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/msgpack/fallback.py b/msgpack/fallback.py
index 824f59d5..e219786e 100644
--- a/msgpack/fallback.py
+++ b/msgpack/fallback.py
@@ -582,7 +582,10 @@ def __next__(self):
     next = __next__
 
     def skip(self):
-        self._unpack(EX_SKIP)
+        try:
+            self._unpack(EX_SKIP)
+        except RecursionError:
+            raise StackError
         self._consume()
 
     def unpack(self):
diff --git a/test/test_except.py b/test/test_except.py
index a3bf4675..1e9c0045 100644
--- a/test/test_except.py
+++ b/test/test_except.py
@@ -97,6 +97,11 @@ def test_invalidvalue():
     with raises(StackError):
         unpackb(b"\x91" * 3000)  # nested fixarray(len=1)
 
+    with raises(StackError):
+        unpacker = Unpacker()
+        unpacker.feed(b"\x91" * 3000)
+        unpacker.skip()
+
 
 def test_no_memory_leak_on_nested_invalid_tag() -> None:
     """Regression test: unpacking nested arrays containing an invalid tag must not leak objects."""