question about XMS programming

This is a discussion on question about XMS programming within the C++ Programming forums, part of the General Programming Boards category; HI, i'm programming on XMS with TurboC under DOS, the program will be right when i compile it with Small ...

  1. #1
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    question about XMS programming

    HI,
    i'm programming on XMS with TurboC under DOS, the program will be right when i compile it with Small Model. but when i compile it with Large Model, the program gets bad, the error is that calling XMS driver entry function, the program will get a Divided-By-Zero error.
    i don't know why it is caused, and how to solve it.
    Nana C++ Library is a GUI framework that designed to be C++ style, cross-platform and easy-to-use.

  2. #2
    Frequently Quite Prolix dwks's Avatar
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    Obviously, a divide-by-zero error is a program trying to go x/0. I don't know what would cause it if the program worked under the small model. Post the program in question (the code, that is).
    dwk

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    Code:
    static void far(* __xms_driver)(void) = 0; //it stores the xms driver entry function address
    
    bool xmsInit(void) //get the xms driver entry function
    {
       union  REGS  r;
       struct SREGS s;
       unsigned long driver_entry = 0;
       
       
       if(__xms_driver != 0) return true;   
    
       r.x.ax = 0x4300;  
       int86(0x2f, &r, &r);
       if(r.h.al != 0x80)
            return false;
            
       segread(&s);
       r.x.ax = 0x4310;
       int86x(0x2f, &r, &r, &s); 
       
       driver_entry = s.es;
       driver_entry <<= 16;
       driver_entry += r.x.bx;
       __xms_driver = (void (far*)())driver_entry;
       return true; 
    }
    
    bool __xms_mem_move(struct __WXMS_TAG far* xms_ptr)
    {
        int segs, offs, status;
    
        int ds_, si_;
        segs = FP_SEG(xms_ptr);
        offs = FP_OFF(xms_ptr);
        
        ds_ = _DS;
        si_ = _SI;
    
          _AH = 0xb;
          _DS = segs;
          _SI = offs;   
    
        __xms_driver(); //crashed here!!!!!!!!!!!!!!!!!!! divided by zero
        status = _AX;
    
        _SI = si_;
        _DS = ds_;
    
        return (status == 1)?(true): (false);
    }
    compiler is TC2, memory model is large, i really dont know what causes the program crashed
    Nana C++ Library is a GUI framework that designed to be C++ style, cross-platform and easy-to-use.

  4. #4
    and the hat of wrongness Salem's Avatar
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    Or join the real world where 640K is just a distant memory of a bygone age.
    Get a 32 bit compiler for heavens sake!
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    Sorry, the OS-platform is MS-DOS 7.1, so i cann't use 32-bit compiler...
    Nana C++ Library is a GUI framework that designed to be C++ style, cross-platform and easy-to-use.

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    Unless you recompile the code for __xms_driver() as a large model, it's probably not going to work.

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    thanks
    swoopy, you meant i have to recompile the code for __xms_driver as small model?? how to do?
    Nana C++ Library is a GUI framework that designed to be C++ style, cross-platform and easy-to-use.

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    >swoopy, you meant i have to recompile the code for __xms_driver as small model?? how to do?
    jinhao, I guess there are three questions:
    1) Do you have the source code for __xms_driver?
    2) Did you compile it as a large model or small model?
    3) If it works as a small model, why are you changing to a large model?

    There's a member who frequents this forum named Bubba who might be able to help you. But he tends to disappear for long periods before reappearing.

  9. #9
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    i found the real place where the divide error caused

    in the __xms_mem_move
    [CODE]
    _AH = 0xb;
    _DS = segs; //it,s here divide error, WHY?
    _SI = offs;
    [CODE]
    Nana C++ Library is a GUI framework that designed to be C++ style, cross-platform and easy-to-use.

  10. #10
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    the problem is that when i change the value of DS in large memory model, the program reports divide error.

    i don't know whether i can chage the value of DS in the large memory model
    Nana C++ Library is a GUI framework that designed to be C++ style, cross-platform and easy-to-use.

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