difficulties making wrapper mex file on linux?

Hi,

First I complied the fcnsuit.c file as follows in a linux terminal:

gcc -c -fPIE fcnsuite.c ld -o fcnsuite.so -shared fcnsuite.o

Then I open matlab and try to make a mex file as follows:

mex mlbsuite.c

Then I get following error message:

mlbsuite.o:In function 'mexFunction':

mlbsuite.c:(.text+0xae): undefined reference to 'dlopen'

mlbsuite.c:(.text+0xd6): undefined reference to 'dlsym'

mlbsuite.c:(.text+0x217): undefined reference to 'dlclose'

          mex: link of ' "mlbsuit.mex64"' failed

How can I fix this?

Answer 1

[Kaustubha Govind]

Looks like you might need to add a

#include <dlfcn.h>

to mlbsuite.c?

[Jarir]

This is the code in mlbsuite.c:

/* OS specific function calls for shared objects and dynamic linking */ { #ifdef WINDOWS

#include windows.h

#include process.h

typedef void (WINAPI * PPROC) (double *, double *, double *, double *, int, int, int, int);

#define LIBHANDLE HANDLE

#define GetProcedure GetProcAddress

#define CloseDynalink FreeLibrary

#else

#include dlfcn.h

#include pthread.h

typedef void (*PPROC) (double *, double *, double *, double *, int, int, int, int);

#define LIBHANDLE void *

#define GetProcedure dlsym

#define CloseDynalink dlclose

#endif

#include "mex.h"

#ifdef _STDC_

void mexFunction (int nlhs, mxArray * plhs[], int nrhs, const mxArray * prhs[])

#else

void mexFunction (nlhs, plhs, nrhs, prhs)

int nlhs, nrhs;

mxArray *plhs[];

const mxArray *prhs[];

#endif

int i, j, m, n, ng, nh, size;

double *H, *G, *F, *X, *tmpptr;
char *fcnname;
PPROC pfcn;
LIBHANDLE hLibrary;
if ((nrhs < 4) || (nlhs < 3))
  {
    mexPrintf ("usage: [f, g, h] = mlbsuite(x, ng, nh, 'function_name');\n");
    mexErrMsgTxt ("example: [f, g, h] = mlbsuite([14.095 0.84296]', 2, 0, 'g06');");
  }
n = mxGetM (prhs[0]);
m = mxGetN (prhs[0]);
X = mxGetPr (prhs[0]);
size = mxGetNumberOfElements (prhs[3]) + 1;
fcnname = mxCalloc (size, sizeof (char));
if (mxGetString (prhs[3], fcnname, size) != 0)
  mexErrMsgTxt ("Could not convert string data.");
#ifdef WINDOWS
hLibrary = LoadLibrary ("fcnsuite.dll");
#else
hLibrary = dlopen ("./fcnsuite.so", RTLD_NOW);
#endif
if (NULL == hLibrary)
  mexErrMsgTxt ("could not load fcnsuite.dll (win32) or fcnsuite.so (linux) file");
pfcn = (PPROC) GetProcedure (hLibrary, fcnname);
if (NULL == pfcn)
  {
    mexPrintf ("procedure %s not found in library file!", fcnname);
    mexErrMsgTxt ("failed to load procedure");
  }
plhs[0] = mxCreateDoubleMatrix (1, m, mxREAL);
F = mxGetPr (plhs[0]);
tmpptr = mxGetPr (prhs[1]);
ng = (int) tmpptr[0];
plhs[1] = mxCreateDoubleMatrix (ng, m, mxREAL);
G = mxGetPr (plhs[1]);
tmpptr = mxGetPr (prhs[2]);
nh = (int) tmpptr[0];
plhs[2] = mxCreateDoubleMatrix (nh, m, mxREAL);
H = mxGetPr (plhs[2]);
for (i = 0; i < m; i++)
  {
    pfcn (&X[i * n], &F[i], &G[i * ng], &H[i * nh], n, 1, ng, nh);
  }
CloseDynalink (hLibrary);
mxFree (fcnname);
}

As you can see

#include dlfcn.h

was already in it.

Thank you for your help.

[Kaustubha Govind]

Ah! Is it just the linking (and not the compiling) that fails? If yes, you may need to link against an additional library using the mex -l option.

[Jarir]

Thank you!

Problem is I am just a newbie in all this. I actually don't know how to do what you are suggesting. Which library do I have to link and how?

[Kaustubha Govind]

Try:

>> mex mlbsuite.c -ldl

[MTA]

Hi I'm having the same problem but when running my simulink model in the accelerator mode (which will compile the model and hence the same problem) The option -ldl is already shows in the compilation commands being executed, I've also provided a link to the libdl.so library so Matlab can see it and still no luck

Cheers

Mohamad

[Kaustubha Govind]

Mohamad: Could you please start a new thread for this if you don't mind? Since you are working with Simulink, there might be other considerations. Also, I would recommend that you post the complete build log in your question. Thanks!

[Jarir]

Kaustubha Govind: Thank you very much! It finally works.