Matlab exception thrown by initialization of mwArray while using c++ shared library

Hello All,

I've been struggling to succeed in using mwArrays in a c++ application with a shared library compiled with matlab compiler. I created a simple function to identify a system in using the system identification toolbox and both the n4sid and pem functions. Currently, I get a fatal error whenever I initialize a mwArray. The exception is thrown in the matlab mclcppclass.h file.:

mwArray GetPromoted(mwSize num_indices, ...)
    {
        va_list vargs;
        va_start(vargs, num_indices);
        array_ref* p = array_ref_getV_int(m_pa, num_indices, vargs);
        va_end(vargs);
        if (!p)
            mwException::raise_error();
        return mwArray(p);
    }

the minimal program is:

#include "libidentify_system.h"

int main()
{
    mclInitializeApplication(NULL,0); 
    mwArray test;
    test(1, 1, mxDOUBLE_CLASS);
    return 0;
}

libidentify_system.h is the .h file generated by MATLAB compiler.

I'm currently compiling using cmake. The relevant lines in the top level cmakelists.txt file are:

cmake_minimum_required(VERSION 3.5.1)
project(MPC_IAT)

set(CMAKE_CXX_STANDARD 14)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -Wshadow \
-Wnon-virtual-dtor -Wpedantic -Wold-style-cast -Wcast-align -Wunused \
-Wconversion  -Woverloaded-virtual -Wsign-conversion \
-Wlogical-op \
-Wuseless-cast -Wdouble-promotion -Wformat=2 -Wno-format-y2k")

include_directories("/usr/local/MATLAB/R2020b/extern/include")

find_package(Threads)

link_directories("/usr/local/MATLAB/R2020b/runtime/glnxa64")
link_directories("/usr/local/MATLAB/R2020b/extern/bin/glnxa64")

add_library(libidentify_system SHARED IMPORTED)
set_property(TARGET libidentify_system PROPERTY IMPORTED_LOCATION "/usr/libidentify_system/application/libidentify_system.so")

add_executable(test
               src/testmw/main.cpp
               src/testmw/libidentify_system.h)           

target_link_libraries(test libidentify_system mwmclmcrrt MatlabDataArray MatlabCppSharedLib ${CMAKE_THREAD_LIBS_INIT})

I'm still pretty new to c++ and cmake so I suspect the error has more to do with incorrect linking or something of that sort. I figure here is not the place to put the whole shared set of files that result from compiling my script, but I've put the stuff in a zip located here (my google drive).

[Aghamarsh Varanasi]

Can you explain the variables in the 'GetPromoted' function ?

Answer 1

[Jonathan Ingber Katz]

The solution was a missing call to mclmcrInitialize() in main.