"dynamic module does not define init function (init_mapnik)" on MacOS

[paberline-rms]

Hi,

I've build both Mapnik (v3.0.13) and it's python mapnik-bindings (v3.0.13) from source on Mac OS 10.11.6 using the standard Clang (v800.0.42.1) build tools.

This seemed to complete OK.

However when I try and import mapnik I get

import mapnik

Traceback (most recent call last):

File "", line 1, in
File "/usr/local/lib/python2.7/site-packages/mapnik-0.1-py2.7-macosx-10.11-x86_64.egg/mapnik/init.py", line 74, in
from ._mapnik import *
ImportError: dynamic module does not define init function (init_mapnik)

this seems to be due to C++ name mangling as suggested here as I can see that _init_mapnik (note the _ prefix) is defined:

nm /usr/local/lib/python2.7/site-packages/mapnik-0.1-py2.7-macosx-10.11-x86_64.egg/mapnik/_mapnik.so | grep init_mapnik 00000000000c6c00 t _init_mapnik

I looked for the init_mapnik definition to see if it was marked extern but can't see it.

Can anyone suggest what I'm doing wrong?

Thanks

[alexey-gl]

Hi, I did the same thing (Mapnik (v3.0.13) and python-mapnik (v3.0.13)) and unfortunately had the same result on CentOS7.

[robinhouston]

I had the same problem (macOS 10.12.4, mapnik 3.0.13, python-mapnik v3.0.13).

It seems to be caused by mapnik being built with the flag -fvisibility=hidden. This flag is picked up via mapnik-config --cflags and used to build python-mapnik, but the python-mapnik code is assuming symbols are visible by default.

The patch below makes it work it for me, by removing the -fvisibility=hidden flag from the compilation options.

diff --git a/setup.py b/setup.py
index 9d9e66501..f535e585a 100755
--- a/setup.py
+++ b/setup.py
@@ -227,6 +227,8 @@ if mason_build:
 
 extra_comp_args = check_output([mapnik_config, '--cflags']).split(' ')
 
+extra_comp_args = filter(lambda arg: arg != "-fvisibility=hidden", extra_comp_args)
+
 if os.environ.get("PYCAIRO", "false") == "true":
     try:
         extra_comp_args.append('-DHAVE_PYCAIRO')

[alexey-gl]

That is fix my problem also!
Thanks a lot!

[artemp]

Thanks for reporting and the fix!

extra_comp_args = list(filter(lambda arg: arg != "-fvisibility=hidden", extra_comp_args))

^ In python3 filters are lazy
/cc @paberline-rms @robinhouston @alexey-gl

[robinhouston]

Thanks @artemp! Can you cherry-pick this into the v3.0.x branch as well?

[artemp]

@robinhouston - yep, done.