Linking errors from MATLAB Mex library

Question

I am having troubling compiling a MATLAB Mex library - specifically, the 'Correlation Clustering Optimization' code from this website. I am trying to compile on an OSX machine, and am using the supplied `mexall` function. This runs the following line: ``` mex -O -largeArrayDims CXXFLAGS="\$CXXFLAGS -Wno-write-strings" QPBO.cpp QPBO_extra.cpp QPBO_maxflow.cpp QPBO_wrapper_mex.cpp QPBO_postprocessing.cpp -output QPBO_wrapper_mex ``` The error occurs at linking time with the following output to the MATLAB command line: ``` ld: duplicate symbol QPBO<int>::GetMaxEdgeNum() in QPBO_extra.o and QPBO.o collect2: ld returned 1 exit status mex: link of ' "QPBO_wrapper_mex.mexmaci64"' failed. ``` Judging from this, the function `GetMaxEdgeNum` is appearing in both `QPBO_extra.o` and `QPBO.o`. However, it is only actually defined in a header file, `QPBO.h`. I therefore suspect that both source files which include it are including it as a symbol in their object files, causing a problem at link time…

Accepted Answer

It seems like the issue is that some template code is in .cpp files.

- Remove the `#include instances.inc` declarations from the `.cpp` files.

- Move all code from QPBO.cpp, QPBO_extra.cpp, QPBO_maxflow.cpp and QPBO_postprocessing.cpp to the header file qpbo.h.

- You'll have now a single .cpp file qpbo_wrapper_mex.cpp and a single header qpbo.h

mex the file (in matlab) using:

```
>> mex -O -largeArrayDims qpbo_wrapper_mex.cpp
```

Should work...

Linking errors from MATLAB Mex library

Solution

Problem