Matlab 2018b - Ubuntu 18.04 - Missing Gateway function

[DWolfr]

Hi everyone,

i have been installing NLopt using the Ubuntu 18.04 normal CMake version (3.10.2), with

cmake -DMatlab_ROOT_DIR=/usr/local/MATLAB/R2018b/ -DCMAKE_INSTALL_PREFIX=$HOME/NLopt/install -DINSTALL_MEX_DIR=$HOME/NLopt/matlab/ -DNLOPT_PYTHON=OFF -DNLOPT_OCTAVE=OFF -DNLOPT_GUILE=OFF -DNLOPT_SWIG=OFF ..

(from a sub directory 'build') for the usage with Matlab 2018b. After

make
make install

i tried to run the matlab script

opt.algorithm = NLOPT_LD_MMA
opt.lower_bounds = [-inf, 0]
opt.min_objective = @myfunc
opt.fc = { (@(x) myconstraint(x,2,0)), (@(x) myconstraint(x,-1,1)) }
opt.fc_tol = [1e-8, 1e-8];
opt.xtol_rel = 1e-4
​
[xopt, fmin, retcode] = nlopt_optimize(opt, [1.234 5.678])
​
function [val, gradient] = myfunc(x)
    val = sqrt(x(2));
    if (nargout > 1)
        gradient = [0, 0.5 / val];
    end
end
function [val, gradient] = myconstraint(x,a,b)
    val = (a*x(1) + b)^3 - x(2);
    if (nargout > 1)
        gradient = [3*a*(a*x(1) + b)^2, -1];
    end
end

and received the error

Invalid MEX-file '/home/USERNAME/NlpSolver/NLopt/matlab/nlopt_optimize.mexa64': Gateway function is
missing.
​
Error in untitled (line 8)
[xopt, fmin, retcode] = nlopt_optimize(opt, [1.234 5.678])

I found the issue robotology/blockfactory#4, which describes an problem between CMake (namely the FindMatlab.cmake) and Matlab Version 2018b.
The newer versions of CMake got a fix, which solves this problem https://gitlab.kitware.com/cmake/cmake/issues/18391 .

I found an fix for the combination between CMake version 3.10.2 and Matlab version 2018b in robotology-dependencies/qpOASES#11, where the the new CMake FindMatlab.cmake (https://raw.githubusercontent.com/Kitware/CMake/v3.14.3/Modules/FindMatlab.cmake) file should be copied in the local 'cmake' folder of the repository and robotology-dependencies/qpOASES@899afd8 should be applied.

This solves the problem locally, such that the given Matlab example is working.

Is there an other (better) workaround for this problem?

[stevengj]

From reading the linked PR, it seems the problem was that mexFunction here was not getting exported.

Short of waiting for a new cmake release that incorporates the fix, we might be able to just add __declspec(dllexport) to our function definition?

Can you try patching src/octave/nlopt_optimize-mex.c to add the following line before void mexFunction(...) to see if it fixes the problem?

#ifdef _MSC_VER
__declspec(dllexport)
#endif

[DWolfr]

Thank you for your fast reply, I tested your fix, but it is not working. The same error remains

Invalid MEX-file '/home/disi/tmp/nlopt/matlab/nlopt_optimize.mexa64': Gateway function is missing.

Error in untitled (line 8)
[xopt, fmin, retcode] = nlopt_optimize(opt, [1.234 5.678])

[jschueller]

are you sure it got rebuilt and installed after patching ?

[DWolfr]

I erased the the whole repo and the $HOME/NLopt/matlab/ matlab folder and rebuild everything with the suggested patch from @stevengj. Unfortunately the error is not fixed.

[jschueller]

oh, right, this patch should not be needed on Linux, only for msvc.
could you give us the output of
nm nlopt_optimize.mexa64 | grep mexFunction

if this returns nothing you can try to add DLL_EXPORT_SYM before "void mexFunction", or directly __attribute__ ((visibility ("default")))

[EABN]

Thanks, @DSieb! I updated CMake to version 3.10.2 and then I could use NLopt in Matlab 2018b - Ubuntu 18.04.

[nicolapiccinelli]

I have the same problem on Ubuntu 18.04, any idea about?

• CMake version 3.10.2
• Matlab 2019b
• GCC 7.4.0

the output of nm nlopt_optimize.mexa64 | grep mexFunction is 0000000000002590 t mexFunction

[nicolapiccinelli]

I've solved the issue adding to the CMakeLists.txt in the octave folder the following line set_target_properties(nlopt_optimize-mex PROPERTIES COMPILE_FLAGS "-fvisibility=default")
after the matlab_add_mex and then recompile.

[jschueller]

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