Creating DLL in MS VS 6.0 in C

This is a discussion on Creating DLL in MS VS 6.0 in C within the C Programming forums, part of the General Programming Boards category; Using Visual Studio 6 C++ (but programming C) 1. Have created new project of type Win32 Dynamic Link Library. 2. ...

  1. #1
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    Creating DLL in MS VS 6.0 in C

    Using Visual Studio 6 C++ (but programming C)

    1. Have created new project of type Win32 Dynamic Link Library.

    2. Have got all c code (i.e. imported from standard project I made earlier), headers and external dependancies set up and imported.

    3. Have turned of precompiled headers.

    4. In main () I have included:

    Code:
    #include <windows.h>
    #include <dos.h>
    5. I have been following instuctions as outlined in this web link
    http://support.microsoft.com/default...b;en-us;106553

    I cant go any further in this link when I try to compile because I get these strange compile errors.

    Code:
    c:\program files\microsoft visual studio\vc98\include\windef.h(43) : warning C4114: same type qualifier used more than once
    c:\program files\microsoft visual studio\vc98\include\windef.h(43) : error C2632: 'long' followed by 'long' is illegal
    c:\program files\microsoft visual studio\vc98\include\windef.h(43) : warning C4091: 'typedef ' : ignored on left of 'unsigned long ' when no variable is declared
    c:\program files\microsoft visual studio\vc98\include\windef.h(45) : warning C4114: same type qualifier used more than once
    c:\program files\microsoft visual studio\vc98\include\windef.h(45) : error C2632: 'short' followed by 'short' is illegal
    c:\program files\microsoft visual studio\vc98\include\windef.h(45) : warning C4091: 'typedef ' : ignored on left of 'unsigned short ' when no variable is declared...........
    and so on..

    Does anyone have any any clear and comprehensive instuctions, web links etc on how you accomplish making dll's in this envionment - as I think the link I am following is out of date (and a little confusing, as I have never created a dll before).

    Many thanks
    Simon
    Last edited by earnshaw; 01-12-2005 at 10:44 AM.

  2. #2
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    It looks like you are trying to compile C code as C++.

  3. #3
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    This is C code, and I want instructions to compile a DLL in C - but I'm using Visual C++, because you can make it compile in C - and I have successfully made C programs in the past using this method, so I am a bit reluctant to try other compilers.

  4. #4
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    Quote Originally Posted by earnshaw
    Using Visual Studio 6 C++ (but programming C)


    I cant go any further in this link when I try to compile because I get these strange compile errors.

    Code:
    c:\program files\microsoft visual studio\vc98\include\windef.h(43) : warning C4114: same type qualifier used more than once
    c:\program files\microsoft visual studio\vc98\include\windef.h(43) : error C2632: 'long' followed by 'long' is illegal
    and so on..

    Does anyone have any any clear and comprehensive instuctions, web links etc on how you accomplish making dll's in this envionment - as I think the link I am following is out of date (and a little confusing, as I have never created a dll before).

    Many thanks
    Simon
    Visual Studio 6 doesn't have long long data types (at least mine doesn't).
    You might want to get Visual C++ 2005 Express. (Free download).

    If you want to use VS6, the data type is __int64:

    Code:
    /* use of 64-bit ints with Microsoft Visual Studio 6 */
    #include <stdio.h>                                    
    typedef unsigned __int64 Long; /* typedef for my convenience */
    int main()                                       
    {                                                     
       Long juul = 123456789012345678L;    
    
       printf("sizeof(Long) = %d\n", sizeof (Long));
       printf("juul: %I64d (decimal)\n",juul);
       printf("juul: 0x%016I64X (hex)\n",juul);                     
       return 0;
    }
    Regards,

    Dave
    Last edited by Dave Evans; 01-12-2005 at 02:38 PM.

  5. #5
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    Download the newest version of the platform SDK, and use those header files instead. My version of windef.h compiles just fine with visual c++.

  6. #6
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    I found that I could compile ok a C++ dll (no surprise there). I was just testing it and seeing what was involved. I then tried to compile the same code, but as C, and it didnt work, which didnt surprise me really, but I was holding out for some simple errors. However the errors seem odd and unfixable, so I must have to change some things in the header file I think the DEF file I have will be ok for Visual Basic 6.

    Here is an example of the errors.

    Code:
    Compiling...
    c_dll_4_vb.c
    c:\cprogs\c_dll_4_vb\c_dll_4_vb.h(9) : error C2143: syntax error : missing ')' before '&'
    c:\cprogs\c_dll_4_vb\c_dll_4_vb.h(9) : error C2143: syntax error : missing '{' before '&'
    c:\cprogs\c_dll_4_vb\c_dll_4_vb.h(9) : error C2059: syntax error : '&'
    c:\cprogs\c_dll_4_vb\c_dll_4_vb.h(9) : error C2059: syntax error : ')'
    c:\cprogs\c_dll_4_vb\c_dll_4_vb.c(5) : error C2143: syntax error : missing ')' before '&'
    c:\cprogs\c_dll_4_vb\c_dll_4_vb.c(5) : error C2143: syntax error : missing '{' before '&'
    c:\cprogs\c_dll_4_vb\c_dll_4_vb.c(5) : error C2059: syntax error : '&'
    c:\cprogs\c_dll_4_vb\c_dll_4_vb.c(5) : error C2059: syntax error : ')'
    Error executing cl.exe.
    I suppose the question I should be asking is what do I need in the header file and what format should the C file be in e.g. what keywords, includes should I be using, also are there any settings I should configure in the Project->Settings?

    Thanks

  7. #7
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    Post the contents of c_dll_4_vb.h and c_dll_4_vb.c

  8. #8
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    This is the c code


    #include "c_dll_4_vb.h"


    Code:
    long __stdcall Resolve_Name_To_Ip
      (char *pcDomainToResolve, char szReturnIP[500], int &iSize)
    {
    	  WSADATA		wsaData;					
    	  LPTSTR		CompName = new char[255];
    	  LPDWORD		CompSize = new unsigned long(255);
    
    	  struct		sockaddr_in dest;
    	  struct		hostent *hp;
    	  char			*dest_ip;
    
    	  unsigned int	addr = 0;
    
    	  strcpy(CompName,pcDomainToResolve);
    
    	  if(WSAStartup(MAKEWORD(2,1), &wsaData) != 0)
    	  {  WSACleanup();
    		 return -100;
    	  }
    
    	  hp = gethostbyname(CompName);
    	  if(!hp)
    	  {  addr = inet_addr(CompName);	
    	  }
    
    	  if((!hp) && (addr == INADDR_NONE))
    	  {// Unable to resolve domain ip.
    		WSACleanup();
    		return -200;
    	  }
    
    	  hp = gethostbyname(CompName);
    	  if(hp != NULL)
    		memcpy(&(dest.sin_addr),hp->h_addr,hp->h_length);
    	  else
    		dest.sin_addr.s_addr = addr;
    
    	  if(hp)
    		dest.sin_family = hp->h_addrtype;
    	  else
    		dest.sin_family = AF_INET;
    
    	  dest_ip = inet_ntoa(dest.sin_addr);
    		
    	  iSize = strlen(dest_ip);
    		
    	  // Allow the string to return to the proper size.
    	  strncpy(szReturnIP, dest_ip, strlen(dest_ip)); 
    		
    	  dest_ip = NULL;
    	  hp = NULL;
    	  addr = 0;
    	  dest.sin_family = NULL;
    	  dest.sin_addr.s_addr = NULL;	
    	  dest.sin_addr.S_un.S_addr = NULL;
    	  dest.sin_port = NULL;
    
    	  delete [] CompName;
    	  delete [] CompSize;
    
    	  WSACleanup();
    	  return (0);
    }

    This is the header:

    Code:
    #include <windows.h>
    #include <winsock.h>
    #include <stdio.h>
    
    // Function is used to resolve a domain name to an IP address.
    // The return values are: -100 = Incorrect version of Winsock
    //                        -200 = Cant resolve domain.
    long __stdcall Resolve_Name_To_Ip
        (char *pcDomainToResolve, char szReturnIP[500], int &iSize);

  9. #9
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    That isn't C code. C doesn't have new or delete, and I believe it doesn't have references. Try this:
    Code:
    In c_dll_4_vb.c
    long __stdcall Resolve_Name_To_Ip
      (char *pcDomainToResolve, char szReturnIP[500], int* iSize)
    {
    	  WSADATA		wsaData;					
    	  //LPTSTR		CompName = new char[255];
    	  LPTSTR		CompName = malloc(sizeof(char)*255);
    	  //LPDWORD		CompSize = new unsigned long(255);
    	  LPDWORD		CompSize = malloc(sizeof(unsigned long)*255);
    
    	  struct		sockaddr_in dest;
    	  struct		hostent *hp;
    	  char			*dest_ip;
    
    	  unsigned int	addr = 0;
    
    	  strcpy(CompName,pcDomainToResolve);
    
    	  if(WSAStartup(MAKEWORD(2,1), &wsaData) != 0)
    	  {  WSACleanup();
    		 return -100;
    	  }
    
    	  hp = gethostbyname(CompName);
    	  if(!hp)
    	  {  addr = inet_addr(CompName);	
    	  }
    
    	  if((!hp) && (addr == INADDR_NONE))
    	  {// Unable to resolve domain ip.
    		WSACleanup();
    		return -200;
    	  }
    
    	  hp = gethostbyname(CompName);
    	  if(hp != NULL)
    		memcpy(&(dest.sin_addr),hp->h_addr,hp->h_length);
    	  else
    		dest.sin_addr.s_addr = addr;
    
    	  if(hp)
    		dest.sin_family = hp->h_addrtype;
    	  else
    		dest.sin_family = AF_INET;
    
    	  dest_ip = inet_ntoa(dest.sin_addr);
    		
    	  *iSize = strlen(dest_ip);
    		
    	  // Allow the string to return to the proper size.
    	  strncpy(szReturnIP, dest_ip, strlen(dest_ip)); 
    		
    	  dest_ip = NULL;
    	  hp = NULL;
    	  addr = 0;
    	  //dest.sin_family = NULL;
    	  //dest.sin_addr.s_addr = NULL;	
    	  //dest.sin_addr.S_un.S_addr = NULL;
    	  //dest.sin_port = NULL;
    	  dest.sin_family = 0;
    	  dest.sin_addr.s_addr = 0;	
    	  dest.sin_addr.S_un.S_addr = 0;
    	  dest.sin_port = 0;
    
    	  free(CompName);
    	  free(CompSize);
    
    	  WSACleanup();
    	  return (0);
    }
    
    In c_dll_4_vb.h
    #include <windows.h>
    #include <winsock.h>
    #include <stdio.h>
    
    // Function is used to resolve a domain name to an IP address.
    // The return values are: -100 = Incorrect version of Winsock
    //                        -200 = Cant resolve domain.
    long __stdcall Resolve_Name_To_Ip
        (char *pcDomainToResolve, char szReturnIP[500], int *iSize);
    If I did your homework for you, then you might pass your class without learning how to write a program like this. Then you might graduate and get your degree without learning how to write a program like this. You might become a professional programmer without knowing how to write a program like this. Someday you might work on a project with me without knowing how to write a program like this. Then I would have to do you serious bodily harm. - Jack Klein

  10. #10
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    Have compiled succesfully in C now!
    Out of the code posted here - and I dont fully understand it all, especially WSAStartup - what are the essential prerequisites in order to get any program you write (in C) to work as a dll?

  11. #11
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    WSAStartup : Winsock Addition Startup, inits ws_32.dll no relation to coding a dll but using one.

  12. #12
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    Thanks RezaK

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