MATLAB: How to create Fortran MEX-files using the Watcom Fortran Compiler 11.0

ccompilecrossfortranlanguageMATLABmexwatcom

I am trying to use the Watcom Fortran compiler to create MEX-files.

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We do not support the Watcom Fortran compiler. Check the following link for a list of the compilers that we support:

https://www.mathworks.com/support/requirements/supported-compilers.html

However, the following are some guidelines that may be adopted to create Fortran MEX files using the Watcom Fortran compiler 11.0 and a C-MEX gateway function.

NOTE: This information was sent in to us by a customer and we only recommend this as a reference. This has not been tested by, and therefore is not supported by, MathWorks.

1. Use the "aux" pragma in the C-MEX gateway routine, as described in the Watcom Fortran Programmer's guide under "Mixed Language Programming". This pragma converts calling conventions from C to Fortran and vice versa.

2. MEX routines use stack-based argument passing, as opposed to register-based argument passing. This means that both the C-MEX gateway routine and the Fortran routines must be compiled in this mode. The corresponding compiler options are -3s for Watcom C/C++ and /sc for Watcom Fortran, respectively.

3. Both the C-MEX gateway and the Fortran files must be compiled as "dynamic link library".

Option /bd for both versions.

4. When creating the MEX function using the MEX command, put a Fortran .obj file first. That way, the MEX-file will have the same name as the Fortran .obj file.

5. When creating the MEX function, use the Watcom C/C++ 11.0 options file (wat11copts.bat). However, when you do this, all paths and environment variables are set to the C/C++ compiler. This means that during linking, the Fortran libraries, referred to by the Fortran .obj file(s), are not found. Therefore, place these in your working directory. (It seems that you only need to do this for "flib7s.lib")

The MATLAB Central news-group is also a useful resource for information regarding this process:

http://www.mathworks.com/matlabcentral

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MATLAB: Fortran matlab

Seems like a permissions/UAC issue. Are you running the command from a directory that you have write access to? Also, try copying yprimef.F to a location in your home directory so that the MEX command doesn't attempt to write to the MATLAB installation root (inside C:\Program Files). If that still doesn't work, try starting MATLAB as Administrator and run the command.

MATLAB: Fortran matlab

Stack space typically comes from local variables and intermediate calculations. Try to avoid these for large variables. Use allocatable variables instead, which come from the heap. E.g., this causes the memory for x to come from the stack:

subroutine foo
real*8 x(10000000)

whereas this will cause the memory for x to come from the heap (generally much larger than the stack):

subroutine foo
real*8, allocatable :: x(:)
allocate(x(10000000))
:
deallocate(x)

If an intermediate calculation is causing a stack overflow, e.g. a large matrix calculation, try to break it down into old F77 style do-loops instead.

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