error #5149: Illegal character in statement label field with matlab2016b

I am trying to compile a fortran mex file which is associated with a matlab code. I ran the command ‘mex FileName.f90’ on Matlab 16b and it gave me the “error #5149: Illegal character in statement label field”. I am using Matlab 16b and Intel Parallel Studio XE 2016 for Fortran with Microsoft Visual Studio 2013. I tried to remove the /fixed from mexopts folder as suggested by several posts but still get the same error. Can someone help me to solve the issue? I am quite new to programming. Thank you Prasanna

Answer 1

[sanidhyak]

Hi @Prasanna,

I understand that you are encountering a “Fortran compiler error” while attempting to compile a “.f90” MEX file in MATLAB R2016b using “Intel Parallel Studio XE 2016” and “Microsoft Visual Studio 2013”. This issue commonly arises when the Intel Fortran compiler interprets “.f90” files as fixed-form Fortran, which expects “strict” formatting rules, even though “.f90” files typically use “free-form” syntax.

To resolve this, you will need to explicitly instruct the compiler to use “free-form” syntax by passing the “-free” flag. Kindly refer to the following command that can be executed directly in MATLAB:

mex('-v', 'FileName.f90', 'FCFLAGS=$FCFLAGS -free') 

This ensures that the “.f90” file is compiled correctly using modern Fortran formatting.

Alternatively, you can create or modify a “mexopts” configuration file by running “mex -setup FORTRAN” and editing the relevant line in the generated “.bat” file from:

set FCFLAGS=/c /nologo /MD 

to:

set FCFLAGS=/c /nologo /MD /free 

This change will apply the “/free” flag every time you compile a Fortran MEX file, avoiding the error going forward.

For more details, you may refer to the following official documentations below:

• MATLAB MEX Command: https://www.mathworks.com/help/matlab/ref/mex.html
• Configure Fortran Compiler (“mex -setup”): https://www.mathworks.com/help/matlab/build-fortran-mex-files-1.html
• Intel Fortran Compiler Options Reference: https://www.intel.com/content/www/us/en/docs/fortran-compiler/developer-guide-reference/2025-0/compiler-options-001.html
• Intel Fortran Source Form (Free vs Fixed): https://www.cita.utoronto.ca/~merz/intel_f10b/main_for/mergedProjects/lref_for/source_files/pgbsourc.htm

I hope this helps!