Build issue with Python 3.4.2 Fedora 22

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Greg N

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Jul 24, 2015, 11:09:06 PM7/24/15

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I ran into an issue with an updated version of Fedora 22 with Python 3.4 (python3-3.4.2-6.fc22.x86_64) getting a "template with C linkage" error during virtualenv python 3 pip/easy_install of py-leveldb. Similar issues when attempting to build from source https://pypi.python.org/packages/source/l/leveldb/leveldb-0.193.tar.gz using `python3 setup.py build`.

Details

Distro: Fedora release 22

Python version: python3-3.4.2-6.fc22.x86_64

PIP version: python3-pip-6.0.8-1.fc22.noarch

Example Errors

(py3env)[root@fedora22 ~]# pip install leveldb

[...]

In file included from /usr/include/python3.4m/pyatomic.h:8:0,

from /usr/include/python3.4m/Python.h:53,

from leveldb_ext.h:8,

from leveldb_ext.cc:6:

/usr/include/python3.4m/dynamic_annotations.h:472:3: error: template with C linkage

template <class T>

error: command 'gcc' failed with exit status 1

-------------------------------------------------------------------------------------------------

(py3env)[root@fedora22 ~]# easy_install leveldb

Searching for leveldb

Reading https://pypi.python.org/simple/leveldb/

Best match: leveldb 0.193

Downloading https://pypi.python.org/packages/source/l/leveldb/leveldb-0.193.tar.gz#md5=2952434f2a0ce10c44f58542cc561589

Processing leveldb-0.193.tar.gz

[...]

In file included from /usr/include/python3.4m/pyatomic.h:8:0,

from /usr/include/python3.4m/Python.h:53,

from leveldb_ext.h:8,

from leveldb_ext.cc:6:

/usr/include/python3.4m/dynamic_annotations.h:472:3: error: template with C linkage

template <class T>

error: Setup script exited with error: command 'gcc' failed with exit status 1

-------------------------------------------------------------------------------------------------

[root@fedora22 leveldb-0.193]# python3 setup.py build

running build

running build_ext

building 'leveldb' extension

[...]

In file included from /usr/include/python3.4m/pyatomic.h:8:0,

from /usr/include/python3.4m/Python.h:53,

from leveldb_ext.h:8,

from leveldb_ext.cc:6:

/usr/include/python3.4m/dynamic_annotations.h:472:3: error: template with C linkage

template <class T>

error: command 'gcc' failed with exit status 1

-------------------------------------------------------------------------------------------------

I was able to work past this by adjusting the leveldb_ext.h header to look like:

// Copyright (c) Arni Mar Jonsson.
// See LICENSE for details.


#ifndef __LEVELDB__MODULE__H__
#define __LEVELDB__MODULE__H__


extern "C++" {
#include <Python.h>
}

extern "C" {
#include "structmember.h"

#include <stdlib.h>
#include <stdio.h>
#include <limits.h>
}

#include <leveldb/db.h>
#include <leveldb/write_batch.h>
#include <leveldb/comparator.h>
#include <leveldb/cache.h>


#include <vector>

I am now able to successfully build using `python3 setup.py build` and install with `python3 setup.py install`.

I test py-leveldb while in python3:

$ python3

Python 3.4.2 (default, Jul 9 2015, 17:24:30)

[GCC 5.1.1 20150618 (Red Hat 5.1.1-4)] on linux

Type "help", "copyright", "credits" or "license" for more information.

>>> import leveldb

>>> db = leveldb.LevelDB('./db')

>>> db.Put(b'hello', b'world')

>>> print(db.Get(b'hello'))

bytearray(b'world')

>>>

At this point it only looks like an issue related to Python 3.4+ as there appears to be a Python header which uses C++ leading to error extern "C" if <Python.h> is included. I can work around it by either moving the "#include <Python.h>" out of the extern "C" to just above it or declaring it in extern "C++" like I did in my example above.