cannot find lib path when matlab standalone app calls a mex function

I am trying to deploy an standalone app from my matlab code using mcc on linux. The code calls a mex interface that calls GDAL c libraries from matlab. I got an error of cannot find the gdal lib libgdal.so.20 when it runs to this mex function.

I hypothesize that I have to specify the first argument as the path to the matlab_runtime. This matab runtime path overwrites my LD_LIBRARY_PATH, which contains my GDAL lib path. I need to call GDAL inside of this app running can I cannot find libgdal.so.20. The hypothesis was verified by output LD_LIBRARY_PATH inside of the run. Then I append all gdal dependence to LD_LIBRARY_PATH and call gdal executables (e.g. gdalinfo). The strategy works. But when I switch back to call my mex interface instead of GDAL executables, the same problem occurs again

The code that directly uses GDAL executables (that worked) is below

function testApp(fileName)
disp(getenv('LD_LIBRARY_PATH'))
setenv('LD_LIBRARIES_PATH', [getenv('LD_LIBRARIES_PATH'),':','path_to_my_gdal_lib']);
disp(getenv('LD_LIBRARY_PATH'))
cmd=['!gdalinfo ' fileName];
eval(cmd);
end

The code that uses a compiled mex file is below

function testApp(fileName)
disp(getenv('LD_LIBRARY_PATH'))
setenv('LD_LIBRARY_PATH', [getenv('LD_LIBRARY_PATH'),':',...
    '/raid-13/SFS/xinyis/apps/gdal/2.3.0/lib:',...
    '/raid-13/SFS/xinyis/apps/proj/4.9.3/lib:',...
    '/raid-13/SFS/xinyis/apps/mpfr/4.1.0/lib:',...
    '/raid-13/SFS/xinyis/apps/mpc/1.1.0/lib:',...
    '/raid-13/SFS/xinyis/apps/gmp/6.2.1/lib']);
disp(getenv('LD_LIBRARY_PATH'))
GDALLoad();
end

My GDALLoad.c function works normally in matlab where it was compiled (but not matlab runtime). The code is below

#include "gdal.h"
#include "mex.h"
#ifdef __linux__
#pragma comment (lib,"libgdal.so")
/* linux code goes here */
#elif __APPLE__
#pragma comment (lib,"libgdal.a")
#elif _WIN64
/* windows code goes here */
#pragma comment (lib,"gdal_i.lib")
#else
#error Platform not supported
#endif
void mexFunction( int nlhs, mxArray *plhs[], int nrhs, const mxArray*prhs[] )
{
    if ( nrhs > 0 || nlhs>0 )
    {
        mexErrMsgTxt("no argument is allowed."); 
    	}
    GDALAllRegister();
    OGRRegisterAll();
    }

I used the following comand to compile and generated an runtime app run_testApp.sh

>> mcc -m testApp.m

I use the following command to run this code

$ ./run_testApp.sh /sharedapps/matlab/2021a 'path2mydata'

Answer 1

[Venkat Siddarth Reddy]

Hi Xinyi,

The setenv function sets the environmental variables for that MATLAB session only. The value of that environmental variable outside of MATLAB session would either be the value defined in the operating system's environmental variables or empty character array.

To run the standalone MATLAB application:

• Update the LD_LIBRARIES_PATH variable inside the run_testsApp.sh, as follows:

    #!/bin/sh 
    # ... (other parts of the script) 
     
    # Set the LD_LIBRARY_PATH to include GDAL library paths 
    export LD_LIBRARY_PATH="/raid-13/SFS/xinyis/apps/gdal/2.3.0/lib:/raid-13/SFS/xinyis/apps/proj/4.9.3/lib:/raid-13/SFS/xinyis/apps/mpfr/4.1.0/lib:/raid-13/SFS/xinyis/apps/mpc/1.1.0/lib:/raid-13/SFS/xinyis/apps/gmp/6.2.1/lib:$LD_LIBRARY_PATH" 
     
    # ... (rest of the script) 

This should set the MATLAB Runtime environment with required environmental variables.

I hope this helps!