Setup MEX compiler for R2014a for Linux

Ubuntu 14.04 comes with GCC 4.8. Matlab 2014a only supports up to GCC 4.7. When I use 2013a I can set the mexopts.sh script to use GCC-4.7 by doing the following

1) In matlab, type mex -setup and press 1 to copy mexopts.sh to ~/.matlab/R2013b/mexopts.sh

2) From the terminal, edit the file ~/.matlab/R2013b/mexopts.sh so that CC=’gcc’ change to –> CC=’gcc-4.7′ CCX=’g++’ change to –> CCX=’g++-4.7′

In 2014a the mexopts.sh file does not exist anymore. When I type mex -setup I get the following error:

>> mex -setup C++

Error using mex

No supported compiler or SDK was found. For options, visit http://www.mathworks.com/support/compilers/R2014a/glnxa64.

I know GCC 4.7 is installed because it works for R2013b but how do I set compiler in 2014a?

[Awais Ashfaq]

Hi, I have a similar problem. Where should I copy the mexopts.sh? I can't find any folder MATLABversion? Cheers

Answer 1

[Mukul Rao]

Hi,

Beginning version R2014a, MATLAB automatically configures the mex pseudo compiler to use a supported compiler (such as gcc 4.7x ) on your machine. This leaves the use of the command “mex –setup” redundant unless you would like to use a supported compiler that is different from the default selection, or force MATLAB to use an unsupported compiler.

Did you try mexing a simple mex file like “timestwo.c” to check if the “mex file_name.x” command works on R2014a?

>> copyfile(fullfile(matlabroot,'extern','examples','refbook',...
  'timestwo.c'), '.', 'f');

>> mex timestwo.c

Make sure you have write permission in your current working directory

[Nathan]

Thanks for the response Mukul. I tried your suggestion and it did not work. The only way I found to fix the problem which to change the symbolic link for gcc from 4.8 to 4.7 outside of Matlab. This means any time I call gcc outside of Matlab it will point to gcc-4.7 rather than 4.8.

I have not figured out how to choose the complier inside Matlab without changing the symbolic link.

[SK]

The problem is that if Matlab finds a compiler with a higher version, it starts using it - after emitting a warning. For example when I used mex -setup, I had gcc 4.8 on my system. I got the warning:

Warning: You are using gcc version '4.8.1'. The version of gcc is not    supported. The version currently supported with MEX is
'4.7.x'.

So I installed gcc 4.7 and changed mexopts.sh. But that doesn't change anything. So how do I tell matlab to downgrade to a version that is now available?

Note: I don't want to point gcc and g++ in the usr/bin directory to 4.7 as other applications are also using the higher version.

Please advise.

[Sergey Demyanov]

How did you change your mexopts.h? You need to copy mexopts.h from MatlabRoot"/bin/mexopts.sh to ~/.matlab/"MatlabVersion", and change 1) CC='gcc' on CC='gcc-4.7', 2) CXX='g++' on CXX='g++-4.7'. because 'gcc' and 'g++' are still aliases for higher versions of gcc and g++. You don't need to run mex -setup after that.

[Joao Henriques]

Thank you Sergey, copying mexopts to the home folder and changing the GCC version there was exactly what I needed! If you wrote that as an answer I'd upvote it.

[Awais Ashfaq]

Hi, I have a similar problem. Where should I copy the mexopts.sh? I can't find any folder MATLABversion? Cheers

[wided hechkel]

Hello,

Should i delete the mexopts.sh from MatlabRoot"/bin/mexopts.sh after changing and copying it to ~/.matlab/"MatlabVersion" ?

Answer 2

[JIAWEI WU]

Thanks Sergey, I copied the file mexopts.h as you said, it works here. it cost me one night to fix it, until now, finally, it has been solved. you are so great!

Answer 3

[Dave]

My solution for R2017a on Ubuntu 16.04.

First install the version of GCC Matlab expects:

sudo apt-get install gcc-4.9

Then edit the configuration file to point to this:

cd ~/.matlab/R2017a
sudo chmod 777 mex_C_glnxa64.xml 
gedit mex_C_glnxa64.xml

Within that xml file, replace:

Location="$gcc"

with

Location="/usr/bin/gcc-4.9"

Save file and Matlab should no longer produce wrong version warnings.

[Jay Stanley]

This solution works on R2017b / Ubuntu 17.10

Answer 4

[wided hechkel]

Hello,

Should i delete the mexopts.sh from MatlabRoot"/bin/mexopts.sh after changing and copying it to ~/.matlab/"MatlabVersion" ?

[jie Chang]

Hello,could you tell me where the direction ~/.matlab/“MatlabVersion”is? thank you.