Some examples do not work when building g2o to static libraries

[txq1986]

Hi Rainer,

Thank you for the great g2o work and I am trying to use it.

Are you aware of that some examples do not work when building g2o to static libraries (.a files). For example, I got a bunch of errors of tutorial_slam2d
fatal error in creating cache of type TUTORIAL_CACHE_SE2_OFFSET
addEdge: FATAL, cannot resolve caches for edge 0x23416e0
g2o::Cache* g2o::CacheContainer::createCache(const g2o::Cache::CacheKey&)
fatal error in creating cache of type TUTORIAL_CACHE_SE2_OFFSET
addEdge: FATAL, cannot resolve caches for edge 0x23419a0
...

cmake commands: $cmake -DBUILD_SHARED_LIBS=OFF ../
OS: Ubuntu 14.04

Build to shared libraries are completely perfect and all the examples work well. Do you have an idea what is the possible reasons for it? Thanks

XQ

[jsgaobiao]

I met the same problem.
Have you solved it ? @txq1986

[AlwaysLearningJary]

I have the same problem, I was thinking the different version of g2o wasn't compatible. But I remove all files, and reinstall g2o again, it still doesn't work well.
OS:Ubuntu 14.04

[jlblancoc]

A classic problem with static linking... compiler optimizes out what it thinks is not used, which is a problem with class factories.

The origin of the problem is this:

    Factory* f = Factory::instance();
    HyperGraph::HyperGraphElement* e = f->construct(key.type());

The factory returns nullptr for string "TUTORIAL_CACHE_SE2_OFFSET", which means that this line is not being executed:

  G2O_REGISTER_TYPE(TUTORIAL_CACHE_SE2_OFFSET, CacheSE2Offset);

The trick used in G2O_REGISTER_TYPE() to ensure the automatic registration is not working with static linking.

I know of this problem because I had to switch to a more complex auto-registration macro for a project of mine.
Solutions:

• Forget about static linking...
• Implement something like MRPT_INITIALIZER() in G2O... Basically, to use __attribute__((constructor)); in GCC/CLANG and continue relying on the existing approach for MSVC (so it will not work with static linking, that's a limitation we have!)

Cheers!

[taiping-z]

@jlblancoc

Hi, I am sorry. I do not understand how to implement something like MRPT_INITIALIZER() in G2O.
Do you have any demos for solving this problem?

Thank you!

[kyosho81]

do like this
namespace g2o {
namespace tutorial {

	G2O_REGISTER_TYPE_GROUP(tutorial_slam2d);

	G2O_REGISTER_TYPE(TUTORIAL_VERTEX_SE2, VertexSE2);
	G2O_REGISTER_TYPE(TUTORIAL_VERTEX_POINT_XY, VertexPointXY);

	G2O_REGISTER_TYPE(TUTORIAL_PARAMS_SE2_OFFSET, ParameterSE2Offset);

	G2O_REGISTER_TYPE(TUTORIAL_CACHE_SE2_OFFSET, CacheSE2Offset);

	G2O_REGISTER_TYPE(TUTORIAL_EDGE_SE2, EdgeSE2);
	G2O_REGISTER_TYPE(TUTORIAL_EDGE_SE2_POINT_XY, EdgeSE2PointXY);
}

} // end namespace
int main()
{
return 0;
}

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