IDL CALL_EXTERNAL crashing when passing arguments to C++

Question

I'm trying to run a c++ script from IDL using the CALL_EXTERNAL function. I've been able to get it to work without arguments, but when I try to add an arg, such as a single IDL LONG INT, IDL crashes. with the error:

% CALL_EXTERNAL: Error loading sharable executable.
                 Symbol: main, File = /home/inspired/workspace/TestCode/main.
                 so
                 /home/inspired/workspace/TestCode/main.so: wrong ELF class:
                 ELFCLASS64
% Execution halted at: TEST_EXTERNAL       7
  /home/inspired/IDLWorkspace/Analyze Data/test_external.pro
%                      $MAIN$    

The test code I'm using is as follows.

The C++ code:

#include <iostream>

int main(int argc, char *argv[]) {
    int temp = (int) strtod(argv[1], NULL);
    std:cout<<temp;
    return temp;
}

The IDL code:

pro test_external
 c= call_external('/home/inspired/workspace/TestCode/main.so','main', long(2), /AUTO_GLUE)
 print,c
end

This code is of course practice code, but if I can't get this to work, then there's no way I'll be able to pass a mixture of arrays, and values.

I am aware that IDL passes everything by reference unless stated otherwise. So I've tried both treating the passed argument as a pointer in the C++ code, and setting the /ALL_VALUE keyword to pass the arg as a value. Neither works resulting in the same error as above. I've read about "glue functions" but I have not been able to find a guide to making them (despite every source indicating that it's 'easy for most programmers'" >.>

Anyway, my options are as follows, and if you can help me with any, I'd be eternally grateful:

1. Get this CALL_EXTERNAL function to work
2. Have the C code grab the data it needs from memory somehow
3. Rewrite everything in C++ (you don't need to help with this one)

Thanks in advance.

Answer 1

I think you are trying to mix 32-bit and 64-bit code. It looks like you are compiling your code as 64-bit, but you are running 32-bit IDL. To check this, IDL prints it when it launches or you can check manually:

IDL> print, !version.memory_bits
      64