Linking issue with BulletExample

[severin-lemaignan]

Bullet example fail to link with the following error:

Linking CXX executable bullet
CMakeFiles/bullet.dir/BulletExample.o: In function `Magnum::SceneGraph::AbstractFeature<3u, float>::AbstractFeature<Magnum::SceneGraph::Object<Magnum::SceneGraph::BasicMatrixTransformation3D<float> >, void>(Magnum::SceneGraph::Object<Magnum::SceneGraph::BasicMatrixTransformation3D<float> >&)':
BulletExample.cpp:(.text._ZN6Magnum10SceneGraph15AbstractFeatureILj3EfEC2INS0_6ObjectINS0_27BasicMatrixTransformation3DIfEEEEvEERT_[_ZN6Magnum10SceneGraph15AbstractFeatureILj3EfEC5INS0_6ObjectINS0_27BasicMatrixTransformation3DIfEEEEvEERT_]+0x1f): undefined reference to `Magnum::SceneGraph::AbstractFeature<3u, float>::AbstractFeature(Magnum::SceneGraph::AbstractObject<3u, float>&)'
collect2: error: ld returned 1 exit status

Compiler (GCC 4.7) was called like that:

/usr/bin/c++    -std=c++0x -Wall -Wextra -Wold-style-cast -Winit-self -Werror=return-type -Wmissing-declarations -pedantic -fvisibility=hidden -Wzero-as-null-pointer-constant -Wdouble-promotion    CMakeFiles/bullet.dir/BulletExample.o  -o bullet  -L/usr/local/lib -rdynamic /usr/local/lib/libMagnum.so /usr/local/lib/libCorradeUtility.so /usr/local/lib/libCorradePluginManager.so /usr/local/lib/libCorradeUtility.so -ldl -lGL /usr/local/lib/libMagnumBulletIntegration.so -lBulletDynamics -lBulletCollision -lLinearMath -lBulletSoftBody /usr/local/lib/libMagnumDebugTools.so /usr/local/lib/libMagnumSceneGraph.so /usr/local/lib/libMagnumShaders.so /usr/local/lib/libMagnumShapes.so /usr/local/lib/libMagnumGlutApplication.a -lglut -lXmu -lXi /usr/local/lib/libCorradePluginManager.so -ldl -lGL /usr/local/lib/libMagnumBulletIntegration.so -lBulletDynamics -lBulletCollision -lLinearMath -lBulletSoftBody /usr/local/lib/libMagnumDebugTools.so /usr/local/lib/libMagnumSceneGraph.so /usr/local/lib/libMagnumShaders.so /usr/local/lib/libMagnumShapes.so /usr/local/lib/libMagnumGlutApplication.a -lglut -lXmu -lXi -Wl,-rpath,/usr/local/lib 

Looks similar to magnum-bootstrap issue 3

EDIT: the issue was that libmagnum was compiled with clang with the sample was compiled with gcc. Using the same compiler for both solved the issue.

[mosra]

Sorry, can't reproduce with GCC 4.7.3. The linking command is the following (I installed Magnum into /usr, but everything else seems to be the same):

/usr/bin/g++-4.7    -std=c++0x -Wall -Wextra -Wold-style-cast -Winit-self -Werror=return-type -Wmissing-declarations -pedantic -fvisibility=hidden -Wzero-as-null-pointer-constant -Wdouble-promotion    CMakeFiles/bullet.dir/BulletExample.cpp.o  -o bullet -rdynamic -lMagnum -lCorradeUtility -lCorradePluginManager -lCorradeUtility -ldl -lGL -lMagnumBulletIntegration -lBulletDynamics -lBulletCollision -lLinearMath -lBulletSoftBody -lMagnumDebugTools -lMagnumSceneGraph -lMagnumShaders -lMagnumShapes -Wl,-Bstatic -lMagnumGlutApplication -Wl,-Bdynamic -lglut -lXmu -lXi -lCorradePluginManager -ldl -lGL -lMagnumBulletIntegration -lBulletDynamics -lBulletCollision -lLinearMath -lBulletSoftBody -lMagnumDebugTools -lMagnumSceneGraph -lMagnumShaders -lMagnumShapes -Wl,-Bstatic -lMagnumGlutApplication -Wl,-Bdynamic -lglut -lXmu -lXi

First four lines of nm /usr/lib/libMagnumSceneGraph.so | grep AbstractFeature | grep AbstractObject indicate that the symbol is present in the library:

000000000001d960 W _ZN6Magnum10SceneGraph15AbstractFeatureILj2EfEC1ERNS0_14AbstractObjectILj2EfEE
000000000001d960 W _ZN6Magnum10SceneGraph15AbstractFeatureILj2EfEC2ERNS0_14AbstractObjectILj2EfEE
000000000001dd20 W _ZN6Magnum10SceneGraph15AbstractFeatureILj3EfEC1ERNS0_14AbstractObjectILj3EfEE
000000000001dd20 W _ZN6Magnum10SceneGraph15AbstractFeatureILj3EfEC2ERNS0_14AbstractObjectILj3EfEE
...

[severin-lemaignan]

Yes, strangely enough, it seems that the symbols are defined for me as well:

$ nm /usr/local/lib/libMagnumSceneGraph.so | grep AbstractFeature | grep AbstractObject
0000000000012350 W _ZN6Magnum10SceneGraph15AbstractFeatureILj2EfEC2ERNS0_14AbstractObjectILj2EfEE
0000000000012660 W _ZN6Magnum10SceneGraph15AbstractFeatureILj3EfEC2ERNS0_14AbstractObjectILj3EfEE
[...]

I've tried to change the order of the lib in the compiler cmd line, without much success...

Do you have a clue why the symbols were listed twice each in your case?

[severin-lemaignan]

Well, the only difference I see between your mangled symbols is C2 and C1 (+ the obvious 2u/3u template specialization).

This distinction between C1 and C2 does not exist in my case (I've only the symbols with C2).

According to this spec, the distinction is:

<ctor-dtor-name> ::= C1 # complete object constructor
           ::= C2   # base object constructor

Does it makes somehow sense to you?

[mosra]

As far as I know, this has someting to do with template instantiation and weak symbols -- the template can be instantiated (and added to symbol table) more than once without error.

I compiled Magnum with GCC 4.7, which added the symbols twice. Now I tried to build it with Clang and it has the symbol only once, just like in your case. I conclude that this is some weird compiler incompatibility -- try to build the examples with Clang too (or build Magnum with GCC 4.7).

[severin-lemaignan]

Well spotted! It indeed fixes the link error, and the demo runs fine!

Is it something we should check & enforce (samples/bootstraps use the same compiler as the main lib)? it may not be a very common issue, though...