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C++/function declarations/prototypes


Hi David,

1) Still MS Visual C++ 6.0 professional

2) Ok, the last reply you sent was very helpful, and has let me move forward a lot.  But, in getting rid of one of the problems ive come across another.

I wanted to split a record into a structure field, and you suggested changing one of my lines.  I'll just copy the suggestion you made.

3. The line

aUnion.struct1.code = array[4]; //**** error c2440: '=' cannot convert from 'char' to 'char [6]'

Is incorrect. The right-hand-side is a character (the fifth character in array 'array'), while the left-hand-side is an array of six characters. If you are trying to store the contents of 'array' into 'code', you might try something like this:

lstrcpyn(&I_STR.code, array, 6);

Now, when i run the program it all runs fine except for the line you suggested which produces the error:

"C:\Documents and Settings\John\My Documents\Computeach\otago_MODIFIED.cpp(173) : error C2065: 'lstrcpyn' : undeclared identifier

My question is what do I have to do to fix this, to declare the function.  To be honest, I had never heard of "lstrcpyn" till you had suggested it, and so I have been doing quite a bit of reading and think I understand the actual function.  Now, if I have been reading correctly, the line you suggested was the actual function, but if I want the function to work I need a function pototype which will tell the compiler how to work the function itself. I have no idea what this is, or how to go about coding it as the books I am trying to learn from are frustratingly vague.

The function would be    lstrcpyn(&I_STR.code, array, 6);

Is making a prototype/declaration the right answer and if so can you suggest how to go about it?  

I dont think you'll need it, but I'll paste the program in below just in case.

thanks for your help



//** Program

  //John Hamilton

   #include <iostream.h>
   #include <fstream.h>
   #include <stdlib.h>
   #include <string.h>
   #include <iomanip.h>
   #include <ctype.h>

//define the structures

   struct I_R_RECORD {        
  char code[6];  //customer code

   struct D_RECORD {       
  char code[6];  //customer code

   struct C_RECORD {      
     char code[6]; //customer code

   const int MAX = 150;
  int main()

//create an instance of the structures, and a pointer to the structures
  struct I_R_RECORD I_STR, *ptr_I;
   struct D_RECORD D_STR, *ptr_D;
   struct C_RECORD C_STR, *ptr_C;

//assign the pointers the structures addresses

  ptr_I = &I_STR;
  ptr_D = &D_STR;
  ptr_C = &C_STR;


//declare input and output files

   ifstream input_file;
  ofstream output_file;
   fstream  outFile, prnFile;

//open input file(test data)"A:532939TD.DAT", ios::in|ios::nocreate);
  if( //check for open failure
     cout << endl << "Could not open the file"
         << endl;

//open output file (validated data)"A:532939VF.DAT", ios::out);
     cout << endl << "File not open"
         << endl;

//open output file (unvalidated data)"A:532939UV.TXT", ios::out);
     cout << endl << "File not open"
         << endl;

//open printer for output"lpt1", ios::out);
//Test for file and printer open failure

   if(!input_file.is_open() | !output_file.is_open() | !outFile.is_open() | !prnFile.is_open())
     cout << endl << "Could not open the file or printer"
        << endl;

//declare arrays

  char  array [MAX];
   char  *array_ptr;
  int num=0, end = 0;
  int total=0;
  int weights[] = { 5,4,3,2},*wptr=weights;      // weights for customer codes
   int pweights[] = { 6,5,4,3,2}, *pwptr=pweights;// weights for part numbers

  // read data from file to array

  while(input_file.peek() !=EOF)
     input_file.getline(array, MAX);

//modulus checks customer codes

  for(num = 0; num < 5; num++)
     array[num] = toupper(array[num]);
  for(array_ptr = array; *(array_ptr+1); array_ptr++)
     num = *array_ptr - '0';
     num *= *wptr;
     total += num;

  end = total % 11;
   end = 11 - end;
  if ((array[4] -'0') == end)

     lstrcpyn(&I_STR.code, array, 6); //** C:\Documents and Settings\John\My Documents\Computeach\otago_MODIFIED.cpp(173) : error C2065: 'lstrcpyn' : undeclared identifier

     output_file << I_STR.code  << endl;    

  else if ((array[4] -'0') != end)
       outFile << I_STR.code  << endl;          


return 0;

John, Thank you for your question.

'lstrcpyn' is a standard function in my Standard Edition Visual C++. I'm not sure why your compiler can't find it. It is declared in file winbase.h, as follows:

   LPSTR lpString1,
   LPCSTR lpString2,
   int iMaxLength
   LPWSTR lpString1,
   LPCWSTR lpString2,
   int iMaxLength
#ifdef UNICODE
#define lstrcpyn  lstrcpynW
#define lstrcpyn  lstrcpynA
#endif // !UNICODE

You might try copying these declarations to your program.

Another possibility is that you could try the renamed function:

   LPCTSTR psz1,
   LPCTSTR psz2,
   int cchMax

Another possibility is that you could try the standard C function:

char *strncpy( char *strDest, const char *strSource, size_t count );

By the way, my expression "&I_STR.code" is wrong. Since 'code' is declared as char[6], it is an array. The name of an array is already an address. "&I_STR.code" would be an attempt to take an address of an address, which makes no sense.

David Spector


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David Spector


Highly knowledgeable in the C++ language, Visual C++ (MSVC), Windows API, documentation and other quality-assurance techniques, and debugging. Knowledgeable in MFC, COM, GUI design, and object-oriented design.


I have been a software engineer since 1965. I have been published. My specializations have been: biomedical programming, compiler implementation, and many kinds of Windows programming. I don't do Databases or other business-oriented stuff.

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