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"Uncaught RuntimeError: memory access out of bounds" when trying to load file in WASM of C-program

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I try to load a file from my local filesystem, which is then loaded into MEMFS (provided by Emscripten) and pass the file name as one argument to a C program which is cross compiled as WebAssembly using Emscripten. When calling the function to load the file I get the error: Uncaught RuntimeError: memory access out of bounds. What am I doing wrong? Are the parameters handed-over incorrectly or is the file access not correct?

C program, has standard main and parameters are passed correctly, loading the file looks like this (in an abstract):

int CLASS main(int argc, const char **argv)
   FILE *ifp;
   const char *ifname;
   // Start - debug code
   for (int i = 0; i < argc; i++)
      // ==> This prints the arguments correctly in the browser console, so the hand-over works.
      printf("argv[%d] = %s\n", i, argv[i]);
   char cwd[1024];
   if (getcwd(cwd, sizeof(cwd)) != NULL)
       // Also prints the MEMFS directory structure correctly.
       printf("Current working directory: %s\n", cwd);
   // End - debug code
   ifname = argv[arg];
   if (!(ifp = fopen(ifname, "rb")))
       perror(ifname);
       continue;
In JavaScript it's called like this:
async _runProgram(args) {
    // Load the emscripten wrapper
    this._dcrawModule = await Module();
    // Convert the JavaScript array to a C-style null-terminated string array
    const paramStrings = args.map((str) => this._dcrawModule.allocateUTF8(str));
    // Allocate memory for the array of pointers
    const paramArray = this._dcrawModule.stackAlloc((paramStrings.length + 1) * 4); 
    paramStrings.forEach((strPtr, i) => {
        this._dcrawModule.setValue(paramArray + i * 4, strPtr, 'i32');
    // Null-terminate the array
    this._dcrawModule.setValue(paramArray + paramStrings.length * 4, 0, 'i32');
    // Call the `_main` method with the parameter array
    return this._dcrawModule['_main'](paramStrings.length + 1, paramArray, 0);
The file itself is loaded into MEMFS doing the following and then the '_runProgram' function is called:
// Create a workspace directory in the emscripten virtual file system and go to it
FS.mkdir('/workspace');
FS.chdir('/workspace');
if (raw_file) {
    FS.createDataFile('/workspace/', 'raw_buf', raw_file, true, true);
    args.push('/workspace/raw_buf');
    //args.push('raw_buf'); //Tried also this and other variants, no success.
this._runProgram(args);
Does anyone has experience with Emscripten, MEMFS, WebAssembly and opening a file in a C-program?
My preference would be to not change the C-program as this is not mine and I want to avoid having to adapt it every time it might be updated in the future (in addition my C knowledge is quite limited :-P)
(full c program can be found here: https://dechifro.org/dcraw/dcraw.c)
Flags used to run the emcc compiler are the following:
FLAGS = -O0 \
          -s ALLOW_MEMORY_GROWTH=1 \
          -s TOTAL_MEMORY=134217728 \
          -s NO_EXIT_RUNTIME=1 \
          -s FORCE_FILESYSTEM=1 \
          --memory-init-file 0 \
          -s MODULARIZE=1 \
          -s WASM=1 \
          -s EXPORT_ES6=1 \
          -s EXPORTED_FUNCTIONS="['_main']" \
          -s EXPORTED_RUNTIME_METHODS=FS,setValue,stringToUTF8,allocateUTF8,stackAlloc  \
          -DNODEPS=1
                What is argv[arg] in the C code? I can see it is supposed to be a pointer to the file name, but what is arg?
– Weather Vane
                Apr 12 at 18:14
                It's the value set in in JavaScript "args.push()" in the snippet above. I tried to pass the fullpath "/workspace/raw_buf", relative "./raw_buf" and only filename "raw_buf".
– niels_h
                Apr 12 at 18:19
                The link containing the full C code shows that arg is a local variable in int CLASS main (int argc, const char **argv) undergoing extensive manipulation.... and then it's the control variable of for ( ; arg < argc; arg++) and there is no break from this loop, so arg ends up out of range of the supplied program arguments.
– Weather Vane
                Apr 12 at 18:24
                Value of "arg" is 2, while parameters passed from JavaScript are for example: argv[0] = -v argv[1] = -i argv[2] = /workspace/raw_buf argv[3] = (null)
– niels_h
                Apr 12 at 18:27
                I am an not interested in arg in the javascript, but in the C code, which has too much knotty code to easily follow: you could use a debugger to find out what the filename being opened is, in the C file. I have not used Emscripten.
– Weather Vane
                Apr 12 at 18:28
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