Failed to call matlab in visual fortran

[yang__rui]

Hi all,

I tried to call MATLAB from visual Fortran, but failed. Could anyone tell me what to do to fix it?

Thanks!

The environment is: 64bit win10; 64bit MATLAB2018a; Intel parallel studio XE 2017fortran + Microsoft visual studio 2017; Debug x64.

The output information in visual studio is:

1>------ Build started: Project: Console2, Configuration: Debug x64 ------

1>Linking...

1>libifcoremdd.lib(for_main.obj) : error LNK2019: unresolved external symbol MAIN__ referenced in function main

1>x64\Debug\Console2.exe : fatal error LNK1120: 1 unresolved externals

1>

1>Build log written to "file://C:\Users\Rui\FORTRAN\Console2\Console2\x64\Debug\BuildLog.htm"

1>Console2 - 2 error(s), 0 warning(s)

========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

The code in Fortran is actually an example (passstr.f) supplied by MATLAB

#include "fintrf.h"
C=====================================================================
#if 0
C     
C     passstr.F
C     .F file needs to be preprocessed to generate .for equivalent
C     
#endif
C     
C     passstr.F is an example for illustrating passing a character 
C     matrix from FORTRAN to MATLAB.
C 
C     It passes a string array/character matrix into MATLAB as output
C     arguments rather than placing it directly into the workspace. 
C      
C     Copyright 1984-2009 The MathWorks, Inc.
C     
C=====================================================================
C     Gateway routine
      subroutine mexFunction(nlhs, plhs, nrhs, prhs)

C     Declarations
      implicit none

C     mexFunction arguments:
      mwPointer plhs(*), prhs(*)
      integer nlhs, nrhs

C     Function declarations:
      mwPointer mxCreateString
      integer mexCallMATLAB

C     Pointers to input/output mxArrays:
      mwPointer input(1)

        integer status
        mwSize i, m, n
        character*75 thestring
        character*15 string(5)

C-----------------------------------------------------------------------
C     Create the string to be passed into MATLAB.
      string(1) = 'MATLAB         '
      string(2) = 'The Scientific '
      string(3) = 'Computing      '
      string(4) = 'Environment    '
      string(5) = '   by TMW, Inc.'

C     Concatenate the set of 5 strings into a long string.
      thestring = string(1)
      do 10 i=2,5
         thestring = thestring(:((i-1)*15)) // string(i)
 10   continue

C     Create the string matrix to be passed into MATLAB. 
      input(1) = mxCreateString(thestring)

C     Set the matrix size to be M=15 and N=5.
      m = 15
      call mxSetM(input(1), m)
      n = 5
      call mxSetN(input(1), n)

C     Transpose the resulting matrix in MATLAB because 
C     Fortran stores arrays as column major.
      status = mexCallMATLAB(1, plhs, 1, input, 'transpose')

C     Cleanup the un-freed memory after calling mexCallMATLAB.
      call mxDestroyArray(input(1))

        return
        end

[Steve_Lionel · Accepted solution]

Start over with a new project, and this time select "Static library" instead of "Console Application". When you selected Console Application, you told it you wanted to create a standalone Fortran executable program, but all you have is a subroutine. You want a library instead to be linked with Matlab.

[Steve_Lionel]

Also - see the Matlab documentation for how to integrate a Fortran procedure into your Matlab environment. You can't just "call Matlab" independently.

[mecej4]

Rui Yang, it helps to understand the role of the Mex-file before building it. Your statement, "I tried to call MATLAB from Visual Fortran", is incorrect. The purpose of this example is to create a Mex file (a DLL specific to Matlab) from Fortran source whose function is to send some strings to Matlab; but this is done when Matlab calls the Mex function, not the other way around.

Since the example is part of the standard Matlab distribution, it is well-documented, e.g., see http://www.ece.northwestern.edu/local-apps/matlabhelp/techdoc/matlab_external/ch04cre7.html .

This is how I built the Mex file on Windows for Matlab 2013b (x64). I opened an IFort 64-bit command window, and added the Matlab directory ...\extern\include to INCLUDE and ...\extern\lib\win64\microsoft to LIB.  Next, I built the DLL with the command

ifort /dll /fpp passstr.F libmx.lib libmex.lib /link /export:MEXFUNCTION /out:passstr.mexw64

Then, I opened Matlab, changed to the directory containing the just-produced Mex file, and typed "passstr", and saw the results in Matlab.

[yang__rui]

Thank you so much!

mecej4 wrote:

Rui Yang, it helps to understand the role of the Mex-file before building it. Your statement, "I tried to call MATLAB from Visual Fortran", is incorrect. The purpose of this example is to create a Mex file (a DLL specific to Matlab) from Fortran source whose function is to send some strings to Matlab; but this is done when Matlab calls the Mex function, not the other way around.

Since the example is part of the standard Matlab distribution, it is well-documented, e.g., see http://www.ece.northwestern.edu/local-apps/matlabhelp/techdoc/matlab_ext... .

This is how I built the Mex file on Windows for Matlab 2013b (x64). I opened an IFort 64-bit command window, and added the Matlab directory ...\extern\include to INCLUDE and ...\extern\lib\win64\microsoft to LIB.  Next, I built the DLL with the command

ifort /dll /fpp passstr.F libmx.lib libmex.lib /link /export:MEXFUNCTION /out:passstr.mexw64

Then, I opened Matlab, changed to the directory containing the just-produced Mex file, and typed "passstr", and saw the results in Matlab.