From c6a57c10d10a458db1dfd8430d817017629f8b0a Mon Sep 17 00:00:00 2001
From: Jason Rhinelander <jason@imaginary.ca>
Date: Tue, 19 Sep 2017 22:12:46 -0300
Subject: [PATCH] Fix dtype string leak

`PyArray_DescrConverter_` doesn't steal a reference to the argument,
and so the passed arguments shouldn't be `.release()`d.
---
 include/pybind11/numpy.h    |  2 +-
 tests/test_numpy_dtypes.cpp |  3 +++
 tests/test_numpy_dtypes.py  | 13 +++++++++++++
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 3755e890..6fd8fdf3 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -440,7 +440,7 @@ public:
     /// This is essentially the same as calling numpy.dtype(args) in Python.
     static dtype from_args(object args) {
         PyObject *ptr = nullptr;
-        if (!detail::npy_api::get().PyArray_DescrConverter_(args.release().ptr(), &ptr) || !ptr)
+        if (!detail::npy_api::get().PyArray_DescrConverter_(args.ptr(), &ptr) || !ptr)
             throw error_already_set();
         return reinterpret_steal<dtype>(ptr);
     }
diff --git a/tests/test_numpy_dtypes.cpp b/tests/test_numpy_dtypes.cpp
index ddec851f..266b1fe7 100644
--- a/tests/test_numpy_dtypes.cpp
+++ b/tests/test_numpy_dtypes.cpp
@@ -448,4 +448,7 @@ TEST_SUBMODULE(numpy_dtypes, m) {
 
     // test_register_dtype
     m.def("register_dtype", []() { PYBIND11_NUMPY_DTYPE(SimpleStruct, bool_, uint_, float_, ldbl_); });
+
+    // test_str_leak
+    m.def("dtype_wrapper", [](py::object d) { return py::dtype::from_args(std::move(d)); });
 }
diff --git a/tests/test_numpy_dtypes.py b/tests/test_numpy_dtypes.py
index 5f9a9540..4818ca4a 100644
--- a/tests/test_numpy_dtypes.py
+++ b/tests/test_numpy_dtypes.py
@@ -293,6 +293,19 @@ def test_register_dtype():
     assert 'dtype is already registered' in str(excinfo.value)
 
 
+@pytest.unsupported_on_pypy
+def test_str_leak():
+    from sys import getrefcount
+    fmt = "f4"
+    pytest.gc_collect()
+    start = getrefcount(fmt)
+    d = m.dtype_wrapper(fmt)
+    assert d is np.dtype("f4")
+    del d
+    pytest.gc_collect()
+    assert getrefcount(fmt) == start
+
+
 @pytest.requires_numpy
 def test_compare_buffer_info():
     assert all(m.compare_buffer_info())