Setting up Matlab mex compilation in Ubuntu

NOTE: This post was updated on January 16, 2012.

Recently I have been trying to compile some Matlab mex-files from the excellent Machine Vision Toolbox by Peter Corke. When I first tried to compile, I got the following warning:

Warning: You are using gcc version "4.6.1-9ubuntu3)".  The version
         currently supported with MEX is "4.3.4".

I tried several ways of "downgrading" gcc, but as it turns out, the newer version of gcc on Ubuntu 11.10 is backwards compatible and works fine. The message above is simply a warning, not an error, and there is no need to change gcc to an older version. However, my real problem was this: I got errors of the type

error: expected expression before ‘/’ token

I had no idea why this error was popping up, until I read a post on similar issues on xcorr. It turns out that C++ style "//" comments are not allowed in the standard mex configuration that is set when you run "mex -setup". To avoid the error, open the mexopts.sh file (mine is located in ~/.matlab/R2011b/mexopts.sh), and replace all occurences of "-ansi" with "-std=c99".