Fix Python 3.8 incompatibility.

6cb584e9de6e8d54f5576c299a308f89bfdcb519.patch

@@ -0,0 +1,81 @@
+From 6cb584e9de6e8d54f5576c299a308f89bfdcb519 Mon Sep 17 00:00:00 2001
+From: Sergei Izmailov <sergei.a.izmailov@gmail.com>
+Date: Tue, 8 Oct 2019 19:25:09 +0300
+Subject: [PATCH] Adapt to python3.8 C API change (#1950)
+
+* Adapt to python3.8 C API change
+
+Do `Py_DECREF(type)` on all python objects on deallocation
+
+fix #1946
+
+* Add bare python3.8 build to CI matrix
+
+While numpy/scipy wheels are available, run python3.8 test without them
+---
+ .travis.yml                     | 27 +++++++++++++++++++++++++++
+ include/pybind11/detail/class.h |  6 ++++++
+ 2 files changed, 33 insertions(+)
+
+diff --git a/.travis.yml b/.travis.yml
+index 381148e04..28f35f995 100644
+--- a/.travis.yml
++++ b/.travis.yml
+@@ -106,6 +106,33 @@ matrix:
+           - lld-7
+           - libc++-7-dev
+           - libc++abi-7-dev  # Why is this necessary???
++  - os: linux
++    dist: xenial
++    env: PYTHON=3.8 CPP=17 GCC=7
++    name: Python 3.8, c++17, gcc 7 (w/o numpy/scipy) # TODO: update build name when the numpy/scipy wheels become available
++    addons:
++      apt:
++        sources:
++          - deadsnakes
++          - ubuntu-toolchain-r-test
++        packages:
++          - g++-7
++          - python3.8-dev
++          - python3.8-venv
++    # Currently there is no numpy/scipy wheels available for python3.8
++    # TODO: remove next before_install, install and script clause when the wheels become available
++    before_install:
++      - pyenv global $(pyenv whence 2to3)  # activate all python versions
++      - PY_CMD=python3
++      - $PY_CMD -m pip install --user --upgrade pip wheel setuptools
++    install:
++      - $PY_CMD -m pip install --user --upgrade pytest
++    script:
++      - |
++        # Barebones build
++        cmake -DCMAKE_BUILD_TYPE=Debug -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -DPYTHON_EXECUTABLE=$(which $PY_CMD) .
++        make pytest -j 2
++        make cpptest -j 2
+   - os: osx
+     name: Python 2.7, c++14, AppleClang 7.3, CMake test
+     osx_image: xcode7.3
+diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
+index ffdfefe74..230ae81ae 100644
+--- a/include/pybind11/detail/class.h
++++ b/include/pybind11/detail/class.h
+@@ -350,6 +350,7 @@ extern "C" inline void pybind11_object_dealloc(PyObject *self) {
+     auto type = Py_TYPE(self);
+     type->tp_free(self);
+ 
++#if PY_VERSION_HEX < 0x03080000
+     // `type->tp_dealloc != pybind11_object_dealloc` means that we're being called
+     // as part of a derived type's dealloc, in which case we're not allowed to decref
+     // the type here. For cross-module compatibility, we shouldn't compare directly
+@@ -357,6 +358,11 @@ extern "C" inline void pybind11_object_dealloc(PyObject *self) {
+     auto pybind11_object_type = (PyTypeObject *) get_internals().instance_base;
+     if (type->tp_dealloc == pybind11_object_type->tp_dealloc)
+         Py_DECREF(type);
++#else
++    // This was not needed before Python 3.8 (Python issue 35810)
++    // https://github.com/pybind/pybind11/issues/1946
++    Py_DECREF(type);
++#endif
+ }
+ 
+ /** Create the type which can be used as a common base for all classes.  This is

pybind11.spec

@@ -15,7 +15,7 @@
 
 Name:    pybind11
 Version: 2.4.2
-Release: 1%{?dist}
+Release: 2%{?dist}
 Summary: Seamless operability between C++11 and Python
 License: BSD
 URL:	 https://github.com/pybind/pybind11
@@ -23,6 +23,8 @@ Source0: https://github.com/pybind/pybind11/archive/v%{version}/%{name}-%{versio
 
 # Don't use pip to get path to headers
 Patch1:  pybind11-2.4.0-nopip.patch
+# Patch for Python 3.8 compatibility
+Patch2:  https://github.com/pybind/pybind11/commit/6cb584e9de6e8d54f5576c299a308f89bfdcb519.patch
 
 %if %{python2_enabled}
 # Needed to build the python libraries
@@ -101,6 +103,7 @@ This package contains the Python 3 files.
 %prep
 %setup -q
 %patch1 -p1 -b .nopip
+%patch2 -p1 -b .python38
 
 %build
 pys=""
@@ -168,6 +171,9 @@ PYBIND11_USE_CMAKE=true %py3_install "--install-purelib" "%{python3_sitearch}"
 %endif
 
 %changelog
+* Tue Oct 08 2019 Susi Lehtola - 2.4.2-2
+- Fix Python 3.8 incompatibility.
+
 * Sat Sep 28 2019 Susi Lehtola - 2.4.2-1
 - Update to 2.4.2.