use library (gcc) in matlab and error with compile of mex - matlab

Question

I am using Mac OSX (yosemite V 10.10.1) and running MATLAB 2014a on it.
I wanted to use SPAM library (sparse modeling software by J. Mairal) on MATLAB and for that I have to install XCode6.1 (that has gcc). First I type in command window mex -setup and result is shown below:
mex -setup
MEX configured to use 'Xcode with Clang' for C language compilation.
Warning: The MATLAB C and Fortran API has changed to support MATLAB
variables with more than 2^32-1 elements. In the near future
you will be required to update your code to utilize the
new API. You can find more information about this at:
http://www.mathworks.com/help/matlab/matlab_external/upgrading-mex-files-to-use-64-bit-api.html.
To choose a different language, select one from the following:
mex -setup C++
mex -setup FORTRAN
So after that I run the compile.m file in SPAM library and suddenly I saw an error that was:
add_flag =
-mmacosx-version-min=10.6
Warning: Directory already exists.
> In compile at 144
compilation of: -I./linalg/ -I./decomp/ -I./prox/ -I./dictLearn/ dictLearn/mex/mexArchetypalAnalysis.cpp
Building with 'Xcode Clang++'.
clang: warning: argument unused during compilation: '-fopenmp'
Error using mex
ld: warning: directory not found for option '-L/usr/lib/gcc/x86_64-linux-gnu/4.8/'
ld: library not found for -lgomp
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Error in compile (line 439)
mex(args{:});
I don't understand what to do. please help me!

Answer 1

It appears that the actual error is occurring at the point of linking with precompiled libraries. The 2 issues are as follows:
The compile code apparently included in the compile.m file looks like it is intended to compile with gcc (it is trying to include files installed by GCC, possibly even linux-specific ones, are you sure that it's an OSX-compatible toolbox?), and yet the error strongly suggests that you are in fact using clang to compile it - you will either need to change the compiler (easy) or rewrite compile.m (not so easy).
One of the libraries that the code needs to have installed in order to be properly linked hasn't been found. On OSX I think this file should be called libgomp.dylib (any mac afficionados want to confirm this?). If you have it on your computer, then it's not in a directory that clang is looking in. You can confirm the library is installed by running find / | grep libgomp.dylib from the terminal - if it is there, you can add it into the compiler argument in compile.m using the -I /DIRECTORY_HOLDING_LIBRARY syntax.
It is entirely possible that fixing 1. will also remediate 2. - I have never tried using SPAM