FBX Python Bindings fails on Ubuntu because of undefined symbol xmlFree

[Anonymous]

As the title says, FBX Python Bindings fails on Ubuntu.

More precisely, FBX Python Bindings generates FbxCommon.py and fbx.so without any errors, but when I import FbxCommon.py from Python interpreter it fails because of the following exception.

>>> import FbxCommon

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/(my_workspace)/PythonBindings/build/Distrib/site-packages/fbx/FbxCommon.py", line 1, in <module>
    from fbx import *
ImportError: /(my_workspace)/PythonBindings/build/Distrib/site-packages/fbx/fbx.so: undefined symbol: xmlFree

My build environment is as follow:

• OS: ubuntu 18.04.4 LTS
• Python: Python 3.8.3 (conda environment)
• SIP version: 4.19.3 (not the latest one because it is known that it correctly supports the '--sip-module'; https://forums.autodesk.com/t5/fbx-forum/cannot-manage-to-compile-python-fbx-2020-0-1-vs2017-with-py... )
• g++ version: g++ (Ubuntu 7.5.0-3ubuntu1~18.04) 7.5.0

As I debugged this issue, I've found that this issue is strongly related to this topic.

• can not link against libxml2 

The Makefile of Python bindings (PythonBindings/build/Python38_x64/Makefile) generated by sip has the following code in it.

LIBS = -L/(my_workspace)/sdk/lib/gcc/x64/release -lz -lxml2 /(my_workspace)/sdk/lib/gcc/x64/release/libfbxsdk.a 

and it leads to the following command on build

.... ipfbxFbxDouble3.o sipfbxFbxDouble2.o sipfbxFbxDateTime.o sipfbxFbxDistance.o sipfbxFbxBlob.o -L/(my_workspace)/sdk/lib/gcc/x64/release -lz -lxml2 /(my_workspace)/sdk/lib/gcc/x64/release/libfbxsdk.a

However, it seems libfbxsdk.a has to reference xml2, so it should be specified before -lxml2 argument.

I solved this problem by editing SIP module script to generate Makefile like this.

LIBS = -L/(my_workspace)/sdk/lib/gcc/x64/release /(my_workspace)/sdk/lib/gcc/x64/release/libfbxsdk.a -lz -lxml2

but is there any better solution? It's a bit weird to do this every time I use FBX Python Bindings on ubuntu.

I tried to use SIP 4.19.22 but it didn't work.

[regalir]

Hi, I can't say for sure because I don't have access to an Ubuntu machine, but I can see two possible causes:

a) are you sure you have libxml2 properly installed on your machine? On Linux/MacOS, the FBX SDK relies on the fact that both the libxml2 and libz are part of the system libraries.

b) there may be an issue with the sipconfig on Ubuntu.

I have tried to build the FBX Python Bindings on Centos 7.7 and, while I do have the same sequence: -L{fbxsdk_path} -lz -lxml2 {fbxsdk_path}/libfbxsdk.a, the fbx.so did properly compile. Then, when I do import FbxCommon I don't get any unresolved symbols.

/bin/Python2.7 (which is a 2.7.5)

sipconfig.py  located in: /usr/lib64/python2.7/site-packages

/bin/sip version 4.14.6

[Anonymous]

Thank you for your advice.

---

a) are you sure you have libxml2 properly installed on your machine? On Linux/MacOS, the FBX SDK relies on the fact that both the libxml2 and libz are part of the system libraries.

Yes, libxml2 comes with ubuntu, but it is libxml2-dev that is required to build FBX SDK. I installed it by sudo apt install libxml2-dev and I think this will properly install the library.

b) there may be an issue with the sipconfig on Ubuntu.

I have tried to build the FBX Python Bindings on Centos 7.7 and, while I do have the same sequence: -L{fbxsdk_path} -lz -lxml2 {fbxsdk_path}/libfbxsdk.a, the fbx.so did properly compile. Then, when I do import FbxCommon I don't get any unresolved symbols.

/bin/Python2.7 (which is a 2.7.5)

sipconfig.py  located in: /usr/lib64/python2.7/site-packages

/bin/sip version 4.14.6

---

I tried to build FBX SDK with Python2.7, and sip-4.14.6, but it didn't work, either. I cannot figure out why your environment can generate the sequence where -lxml2 comes before libfbxsdk.a, but maybe it is because of the difference between ubuntu and centos.

If anyone knows this cause, please let us know!

[Anonymous]

I installed centos 8 and built the FBX Python bindings, and it worked fine! -lxml2 does come before libfbxsdk.a.

I didn't know but it seems Autodesk's linux support is more like CentOS support. So from now on, I'll use CentOS for developing fbx. Thank you.

[Anonymous]

---

I solved this problem by editing SIP module script to generate Makefile like this.

Could you be a little more specific? I see 124 different files in /sip, and no such line in `fbx_module.sip`. Thank  you!

[Anonymous]

Ah nevermind, found it! Within the `sipconfig.py` file...

[Anonymous]

Yes, that's what I edited. More specifically, I edited line 534 of sipconfig.py like this:

# the original code

libs.extend(self.optional_list("LIBS"))

# I changed to this

libs = self.optional_list("LIBS").extend(libs)

[andreaa6EP2A]

Where is the file that you modified by editing SIP module script to generate Makefile like this. Did you only change "sipconfig.py"?

If I change the sipconfig.py doesn't create the LIBS line correctly of Python bindings (PythonBindings/build/Python38_x64/Makefile) as your.

LIBS = -L/(my_workspace)/sdk/lib/gcc/x64/release /(my_workspace)/sdk/lib/gcc/x64/release/libfbxsdk.a -lz -lxml2

 Can you please help me. 

I Know it works in CentOs, but I'm using Ubuntu 20.04 and I have the same problem as you. G++ 9.