C#

static int LengthSize(string str)
{
    if (str == null)
    {
        return 0;
    }
    return (str.Length * 4) + 3;
}

static char* CharPointerFromString(string str)
{
    if (str == null)
    {
        return null;
    }

    char[] charArr = new char[str.Length];
    for (int i = 0; i < str.Length; i++)
    {
        charArr[i] = str.ToCharArray()[i];
    }

    fixed (char* charPtr = charArr)
    {
        return charPtr;
    }
}

static int Main(string[] args)
{
    printf(CharPointerFromString($"Hello {"DeafMan1983"}!\n"));
}

static string StringFromCharPointer(char* s, bool freePtr = false)
{
    if (s == null)
    {
        return string.Empty;
    }

    char* ptr = s;
    while (*ptr != 0)
    {
        ptr++;
    }

    string result = Encoding.UTF8.GetString((byte*)s, (int) (ptr - s));

    if (freePtr)
    {
        NativeMemory.Free(s);
    }
    return result;
}

string text_txt = Path.GetFileName("text.txt");
char* path = CharPointerFromString(text_txt);
FILE* file = fopen(path, CharPointerFromString("r"));
if (file == null)
{
    printf(CharPointerFromString($"Error: {StringFromCharPointer(path)} not found.\n"));
    return ferror(file);
}

printf(CharPointerFromString($"Success: {StringFromCharPointer(path)} found.\n"));
fclose(file);