What's wrong with this code?

This is a discussion on What's wrong with this code? within the C++ Programming forums, part of the General Programming Boards category; I am trying to write a value 54 to parrallel port and then read it back and put it in ...

  1. #1
    Imperator of Darkness Luciferek's Avatar
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    What's wrong with this code?

    I am trying to write a value 54 to parrallel port and then read it back and put it in a variable, from my research the following code should work provided i have inpout32.dll in my windows/system directory (Which i have):

    Code:
    #include <iostream> 
    #include <conio.h> 
    #include <stdio.h> 
    #include <stdlib.h>  
    #include <malloc.h> 
    
    /*   ----Prototypes of Inp and Outp--- */ 
    short _stdcall Inp32(short PortAddress); 
    void _stdcall Out32(short PortAddress, short data); 
    
    int main()
    {
        short PortVal;
        Out32(0x378,54);
        PortVal = Inp32(0x378);
    }
    Well that code won't even compile in Dev C++... I get compiler error:

    [Linker error] undefined reference to `_Z5Out32ss@8'
    [Linker error] undefined reference to `_Z5Inp32s@4'
    ld returned 1 exit status
    ....[Build Error] [port1.exe] Error 1

    Do i need another compiler or the code is just wrong?

  2. #2
    C++まいる!Cをこわせ! Elysia's Avatar
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    Merely trying to call the functions won't work because the linker has no idea where those functions reside. Therefore, you need to link against the correct .lib file so the linker can locate those functions and fill in the code.
    Proper .lib files can often be found in documentation and comes with libraries that you download.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  3. #3
    Imperator of Darkness Luciferek's Avatar
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    inpout32.dll did not come with any .lib files and all the instructions say to put it in the windows/system directory. well anyway how do I "link" to it? do you have any online tutorials to point me to?

  4. #4
    C++まいる!Cをこわせ! Elysia's Avatar
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    You need to tell the linker to search the .lib file to compile the progran. No .lib file, no program. Simple as that.
    C and C++ requires you to have a .lib file to use it with static linking.
    Otherwise you can use dynamic linking, which required a bit more effort.
    It involves function pointers, along with LoadLibrary, FreeLibrary and GetProcAddress.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  5. #5
    Guest Sebastiani's Avatar
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    something like this should work:

    Code:
    #include <windows.h>
     
    typedef short _stdcall ( * InputProcedure )( short ); 
    typedef short _stdcall ( * OutputProcedure )( short, short ); 
     
    int
    main( void )
    {
          HMODULE library = LoadLibrary( "inpout32.dll" );
          if( library )
          {
                InputProcedure Inp32 = ( InputProcedure )GetProcAddress( library, "Inp32" );
                OutputProcedure Outp32 = ( OutputProcedure )GetProcAddress( library, "Outp32" );
                if( Inp32 && Outp32 )
                {                
                      Out32( 0x378, 54 );
                      short PortVal = Inp32( 0x378 );
                      cout << "recieved from port: " << PortVal << endl;
                }
                else
                {
                      cerr << "GetProcAddress failed" << endl;
                }
                FreeLibrary( library );
          }
          else
          {
                cerr << "LoadLibrary failed" << endl;
          }
          return 0;
    }



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