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Jordi Pont-Tuset

I'm from a small town near Girona, Catalunya. Currently in Zürich, Switzerland. Passionate about computer vision, technology, running, and mountains.

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Up until Matlab 2013b, one could modify the C/C++ mex compilation flags by editing the file, usually found in ~/.matlab/ A common example nowadays is adding the -std=c++11 option to compile C++ code from the C++11 standard (which has some awesome features). To do that in Matlab 2013 and below, you would simply add the flag to the CXXFLAGS variable.

In Matlab 2014, however, things got a little bit more complicated than that. Googling a little I found that now the options were stored in XML files called something like mex_C_glnxa64.xml or mex_C++_glnxa64.xml, but these were nowhere to be found in my system, until I finally realized you have to call mex setup before to create them.

The final steps are as follow:

  • Run mex -setup C++ or mex -setup C, depending on which language you are gonna compile. This will create the corresponding XML file.
  • Open the file ~/.matlab/mex_C++_glnxa64.xml or ~/.matlab/mex_C_glnxa64.xml. In some versions of Matlab it’s in ~/.matlab/R2014a/mex_C++_glnxa64.xml.
  • Edit the CXXFLAGS line to something like: CXXFLAGS="-ansi -fexceptions -fPIC -fno-omit-frame-pointer -pthread -std=c++11"

And you’re good to go!

You might also need to change the compiler used to a non-default one. You can do so by calling mex with mex GCC='/path/to/bin/g++' you_file.cpp.