Error "undefined symbol: PL_new_atom" when reading files

[morxa]

When reading files, I always get the following error:

python3: symbol lookup error: /usr/lib64/swipl-7.2.3/lib/x86_64-linux/readutil.so: undefined symbol: PL_new_atom

How to reproduce

1. Copy the following into read.pl

   read_file(Filename, Strings) :-
     setup_call_cleanup(
     open(Filename, read, Stream),
     read_stream_string(Stream, Strings),
     close(Stream)
   ).
   
   read_stream_string(Stream, Strings) :-
     read_line_to_string(Stream, String),
     ( String == end_of_file -> Strings = []
     ;
       read_stream_string(Stream, RStrings),
       Strings = [String|RStrings]
     ).
   

2. Copy the following to read.py:

   from pyswip.prolog import Prolog
   from pyswip.core import *
   
   prolog = Prolog()
   prolog.consult('read.pl')
   list(prolog.query('read_file("read.pl", S)'))
   

3. Run python3 read.py, which will produce the output:

   python3: symbol lookup error: /usr/lib64/swipl-7.2.3/lib/x86_64-linux/readutil.so: undefined symbol: PL_new_atom
   

Workaround

PL_new_atom is defined in libswipl.so, but readutil.so is not linked against libswipl. As a workaround, libswipl.so can be LD_PRELOADed:

$ export LD_PRELOAD=/usr/lib64/swipl-7.2.3/lib/x86_64-linux/libswipl.so.7.2.3
$ python3 read.py

After preloading the shared lib, the error disappears (and #9 occurs). This show that this is indeed a problem with linking.

I'm not sure if this is an error on the pyswip side or the swipl side, but I assume if you always load libswipl.so, then the error will disappear.

This is on Fedora 25 with SWi-Prolog 7.2.3.

[jannikb]

I had a similiar issue while loading the odbc library on ubuntu 16.04 and swi-prolog 7.6.4:
'$open_shared_object'/3: /usr/lib/swi-prolog/lib/amd64/odbc4pl.so: undefined symbol: PL_get_long

The workaround with LD_PRELOAD also worked for me with an adjusted path:
export LD_PRELOAD=/usr/lib/libswipl.so

[yuce]

Thanks @morxa. The test case you provided was very useful. Passing mode=RTLD_GLOBAL to library loader fixed this issue.