Calling Pocketsphinx in C# AccesViolationException

I'm trying to do the pocketsphinx tutorial in C# using pinvoke but get an AccessViolationException when I try to decode using ps_decode_raw().

        IntPtr ps = PocketSphinx.ps_init(config);
        IntPtr fh = Win32Util.fopen(@"goforward.raw", "rb");
        int rv = PocketSphinx.ps_decode_raw(ps, fh, "goforward", -1);

The functions are wrapped as follows

    //ps_decoder_t* ps_init(cmd_ln_t* config)
    [DllImport("pocketsphinx.dll",
        SetLastError = true,
        CallingConvention = CallingConvention.Cdecl)]
    public extern static IntPtr ps_init(
        IntPtr config);

    //int ps_decode_raw(ps_decoder_t *ps, FILE *rawfh, char const *uttid, long maxsamps);
    [DllImport("pocketsphinx.dll",
        SetLastError = true,
        CallingConvention = CallingConvention.Cdecl)]
    public extern static int ps_decode_raw(
        IntPtr ps,
        IntPtr rawfh,
        [MarshalAs(UnmanagedType.LPStr)] string uttid,
        int maxsamps);

    [DllImport("msvcrt.dll",
        SetLastError = true,
        CallingConvention = CallingConvention.Cdecl)]
    public extern static IntPtr fopen(
        [MarshalAs(UnmanagedType.LPStr)] string _Filename,
        [MarshalAs(UnmanagedType.LPStr)] string _Mode);

I wrapped C's fopen as well just because it was the quickest way I can think of implementing the tutorial.

I tried calling cmd_ln_retain on ps to make sure that ps wasn't causing the problem. (it wasn't). I also removed my debug code in the above.

I'm pretty sure something is up with the fopen but I'm not sure what.

Someone asked for the pocketsphinx log. https://justpaste.it/h52t

You don't check for errors anywhere. And it's wrong to set SetLastError to true for these functions. They won't call SetLastError.

Your big problem though is that the library uses a particular instance of the C runtime, depending on how you built it. And your fopen import is from a different instance of the C runtime.

You'll need to add some code to the library that exposes functions to create and destroy FILE* objects. By doing that you'll get a FILE* made by the correct runtime.