I have had an issue in MATLAB 2013a.

The system notices:"Unable to locate a C-compiler required by Stateflow and MATLAB Function blocks. Use 'mex -setup' to select a supported C-compiler."

[Henric Rydén]

Have you tried mex-setup?

Answer 1

[Madhura Suresh]

Are you using a supported compiler for R2013a?

http://www.mathworks.com/support/compilers/R2013a/index.html?sec=win64

After you install a supported compiler, run:

>>mbuild -setup to pick your compiler, and then proceed.