Re: Can't open compiled [pyo~] object

I'm reviving this thread as I again took on trying to open the [pyo~] 
external object in Pd. I know that Pyo has its own channels, but there's 
too little to no activity there. I've already posted quite some time 
ago, but I don't think I'll get an answer there.

I've changed the Makefile to the following (maybe there are mistakes, 
like where the -rdynamic should go or others):

```
# Makefile for pyo~

lib.name = pyo~

class.sources = pyo~.c

cflags =  -rdynamic -I"$(PD_INCLUDE)" -I.. -Wno-cast-function-type 
-Wno-unused-parameter -I/usr/include/python3.11 $(shell pkg-config 
--cflags --embed python3.11)
ldflags = -lpython3.11 $(shell pkg-config --ldflags --embed python3.11)
libs = -L/usr/lib/ $(shell pkg-config --libs --embed python3.11)

datafiles = pyo-help.pd README.md

PDLIBBUILDER_DIR=../pd-lib-builder/
include $(PDLIBBUILDER_DIR)/Makefile.pdlibbuilder
```

The object builds, but I'm still getting the `undefined symbol: 
_Py_NoneStruct` error when I'm trying to load the object. All online 
sources mentioning _Py_NoneStruct refer to the Python shared object, 
which, in my system, is located in 
/usr/lib/python3.11/config-3.11-x86_64-linux-gnu/.

In a filed used to create the object, called m_pyo.h, line 71 reads:

```
#ifdef __linux__
         libpython_handle = dlopen("libpython3.11.so", RTLD_LAZY | 
RTLD_GLOBAL);

```

Anyone savvy in Python-C bindings can help me out?

On 2/23/23 00:01, IOhannes m zmölnig wrote:
> On 2/21/23 20:21, Alexandros wrote:
>>
>> On 21/2/23 20:41, IOhannes m zmölnig wrote:
>>> Am 21. Februar 2023 08:41:48 MEZ schrieb Alexandros <[email protected]>:
>>>> ldflags= $(shell python-config --ldflags)
>>>> libs= $(shell python-config --libs)
>>>>
>>> [...]
>>>> In the pyo~.c file there's a `#include "Python.h"`. Does this mean 
>>>> that I should direct the Makefile to find this file? Because no 
>>>> Python.h file comes with the source code.
>>>
>>> Hopefully so.
>>> python.h is a file provided by python, and it is paramount that you 
>>> build against the header file that matches your python installation.
>>> So you must install the python development files (python3-dev, or 
>>> somesuch).
>>>
>>> I'm not up-to-date when it comes to python C-development, but I  
>>> 'python-config' smells like a deprecated tool.
>> Initially that was python3-config, but in my system, `python` is 
>> Python3, so I thought I change it to `python-config`. Is this still a 
>> deprecated tool?
>
> 1. i was referring to "<foo>-config" being frowned upon in general, as 
> it creates ad-hoc tools with non-normalized interfaces. typically, a 
> preferred way is to use pkg-config or similar tools (that provide a 
> standard way to query compiler/linker flags to build things).
> this is a general observation, but of course the Python folks can 
> still ship (and prefer) their own tool (hence my "I'm not up-to-date 
> when it comes to python C-development")
>
> 2. i *think* the canonical name for the tool is 'python3-config', and 
> you should not arbitrarily change that just becaues you happen to have 
> a 'python-config' script lying somewhere on your disk.
> (afaict, this script can be installed on Debian via the 
> 'python-dev-is-python3' convenience package. i would *not* recommend 
> relying on this, and use canonical names instead (but again, "I'm not 
> up-to-date when it comes to python C-development" so i might be wrong 
> about what the canonical name is).
>
>
> it turns out that 'pkg-config --cflags python3' resp 'pkg-config 
> --libs python3' should do the trick as well.
>
>
> in any case, your real problem is, that your library does not link 
> against the python dynamic library (e.g. libpython3.11).
> i don't know why "python3-config --libs" does not report the 
> apropriate linker flags ("I'm not up-to-date when it comes to python 
> C-development"), but "python3-config --embed --libs" (and you probably 
> should add the '--embed' flag to all invocations of python3-config), 
> as well as "pkg-config --libs python3-embed".
>
>
>
> finally: there's an issuetracker for pyo on 
> <https://github.com/belangeo/pyo/issues> which might be a better place 
> to ask such specific questions.
>
>
> mfg
> IOhannes
>
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