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

IOhannes m zmoelnig via Pd-list <[email protected]> Wed, 2 Jul 2025 12:17:34 +0200
Newsgroups	gmane.comp.multimedia.puredata.general
Message-ID	<[email protected]>
On 5/31/25 11:07, Alexandros Drymonitis wrote:
> 
> I've changed the Makefile to the following (maybe there are mistakes, 
> like where the -rdynamic should go or others):

why is it there in the first place?

> 
> ```
> # 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)


that appears to do an awful lot of unneeded ('-I"$(PD_INCLUDE")' is 
already handled by pd-lib-builder), redundant (e.g. why is "-L/usr/lib/" 
there in the first place? if it is not searched for by default, then 
there's probably a good reason; why do you have *both* the hardcoded 
"/usr/include/python3.11" and a call to pkg-config?) and broken (I don't 
know of any pkg-config that accepts the "--embed" flag) stuff.

anyhow, i've cleaned up the Makefile, like so:


```
# Makefile for pyo~

lib.name = pyo~

class.sources = pyo~.c

PKG_CONFIG := pkg-config
PYTHON=python3

PY_CFLAGS := $(shell $(PKG_CONFIG) --cflags $(PYTHON))
PY_LIBS   := $(shell $(PKG_CONFIG) --libs $(PYTHON))

cflags += $(PY_CFLAGS) -I../
ldlibs += $(PY_LIBS)

datafiles = pyo-help.pd README.md

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

if your python installation does not provide pkgconf scripts for 
"python3", you can pass it on the cmdline like so:
```
make PYTHON=python3.11
```

if you are still not happy with the flags provided by pkgconf, you can 
pass them manually, like so:
```
make PY_CFLAGS="$(python3.11-config --embed --cflags)" 
PY_LIBS="$(python3.11-config --embed --libs)"
```


having said that, I've compiled the external with python3.13 
(Debian/trixie/sid), but...

> 
> The object builds, but I'm still getting the `undefined symbol: 
> _Py_NoneStruct` error 


and I get the same error as well.


as said previously, "I'm not up-to-date when it comes to python 
C-development".
however, force-loading the python-library apparently fixes the problem 
for me:

```
LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libpython3.13.so pd pyo~-help.pd
```

(the help-patch depends on cyclone, but anyhow).

apparently, you should adjust the path to the libpython.so on your system.

also note, that LD_PRELOAD is general not a good idea
(and you should *definitely not* set the environment variable globally,
unless you are really into kneecapping and the like)

> 
> 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);
> 
> ```

no idea where you got the sources from, but afaict current [master] says 
"libpython3.9.so".

in any case, the idea of the code is that it will dynamically load the 
python runtime library to resolve all the symbols.
but this is broken.
afaict, that's because the binaries *really* use the "_Py_NoneStruct" 
symbol directly, rather than deferring the symbol resolution till the 
dlopen() succeeded.
(the consequence is, that fixing the numbers in the dlopen() call, won't 
help).


this wouldn't be a problem is the myo~.pd_linux was linked directly 
against the libpython.
however, `pkg-config --libs python3` does not tell the linker to do so, 
for whatever reasons (afaict, the idea is really to use dlopen() to open 
the library at runtime, rather than adding a hard dependency on the lib).

so my take is, that there is simply some bug on pyo (and probably it 
doesn't show on macOS, because they allow weak-linkage)


in any case, overriding the linker flags fixes this easily:
```
make PY_LIBS="-lpython3.13"
```

alternatively, using "python3.13-config --embed"  should also give you 
the correct flags:

```
make PDLIBBUILDER_DIR=/usr/share/pd-lib-builder/ 
PY_CFLAGS="$(python3.13-config --embed --cflags)" 
PY_LIBS="$(python3.13-config --embed --libs)"
```

(this line is basically just repeating what i already wrote above)


gmasdr
IOhannes



[master] 
<https://github.com/belangeo/pyo/blob/a7cbe87a52330defdede1f31d29ed719712a08a8/embedded/m_pyo.h#L71>



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