Include C++ File to another C++ File

Question

I'm havin a problem in including my files. I got 3 C++ files and all of them got int main(void).

THe problem is whenever i include 1 of them it says that:

function 'int main(void)' already has a body

but if i will remove the int main(void) to other two C++ file this errors will prompt now.

'one or more multiply defined symbols found'
"class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl convertInt(int)" (?convertInt@@YA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@H@Z) already defined in FormatPosDataXml().obj
"class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl convertInt(int)" (?convertInt@@YA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@H@Z) already defined in FormatPosDataXml().obj    

and so forth

this is the codes that i've got:

FormatPosDataXml().cpp

#include <iostream>
#include <sstream>
#include <vector>
#include <string>
#include <cstring>
#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
using namespace std;
#define nextline '\n'
inline bool TextContains(char *text, char ch) {
  while ( *text ) {
    if ( *text++ == ch )
      return true;
  }
  return false;
}
void Split(char *text, char *delims, vector<string> &words) {
  int beg;
  for (int i = 0; text[i]; ++i) {
    while ( text[i] && TextContains(delims, text[i]) )
      ++i;
    beg = i;
    while ( text[i] && !TextContains(delims, text[i]) )
      ++i;
        words.push_back( string(&text[beg], &text[i]) );
  }
}
string convertInt(int number)
{
   stringstream ss;//create a stringstream
   ss << number;//add number to the stream
   return ss.str();//return a string with the contents of the stream
}
string dateFormatChecker(const char *date){
    string strdate=date;
    char getdate[50];
    strcpy_s(getdate, strdate.c_str());
    vector<string> checkdate;
    Split( getdate, "-", checkdate );
    int year, month, day;
    year=atoi(checkdate[0].c_str());
    month=atoi(checkdate[1].c_str());
    day=atoi(checkdate[2].c_str());
    string checkyear, checkmonth, checkday, checkhour, checkminute, checksecond;
            checkyear = convertInt(year);
            if(month<10){
            checkmonth = "0" + convertInt(month);
            }
            else{
            checkmonth = convertInt(month);
            }
            if(day<10){
            checkday = "0" + convertInt(day);
            }
            else{
            checkday = convertInt(day);
            }
            /*
            cout << checkdate[0] << ' ' << checkyear << '\n'
                 << checkdate[1] << ' ' << checkmonth << '\n'
                 << checkdate[2] << ' ' << checkday << '\n';
            */
            if (checkyear.size() != checkdate[0].size()||
                checkmonth.size() != checkdate[1].size()||
                checkday.size() != checkdate[2].size()){
                return "";
            }
    return date;
}
string dateandtimeFormatChecker(const char *dateandtime){
        string strdate=dateandtime;
        char getdateandtime[50];
        strcpy_s(getdateandtime, strdate.c_str());
        vector<string> checkdateandtime;
            Split( getdateandtime, "-: ", checkdateandtime );
        int year, month, day, hour, minute, second;
            year=atoi(checkdateandtime[0].c_str());
            month=atoi(checkdateandtime[1].c_str());
            day=atoi(checkdateandtime[2].c_str());
            hour=atoi(checkdateandtime[3].c_str());
            minute=atoi(checkdateandtime[4].c_str());
            second=atoi(checkdateandtime[5].c_str());
            string checkyear, checkmonth, checkday, checkhour, checkminute, checksecond;
            checkyear = convertInt(year);
            if(month<10){
            checkmonth = "0" + convertInt(month);
            }
            else{
            checkmonth = convertInt(month);
            }
            if(day<10){
            checkday = "0" + convertInt(day);
            }
            else{
            checkday = convertInt(day);
            }
            if(hour<10){
            checkhour = "0" + convertInt(hour);
            }
            else{
            checkhour = convertInt(hour);
            }
            if(minute<10){
            checkminute = "0" + convertInt(minute);
            }
            else{
            checkminute = convertInt(minute);
            }
            if(second<10){
            checksecond = "0" + convertInt(second);
            }
            else{
            checksecond = convertInt(second);
            }
            if (checkyear.size() != checkdateandtime[0].size()||
                checkmonth.size() != checkdateandtime[1].size()||
                checkday.size() != checkdateandtime[2].size()||
                checkhour.size() != checkdateandtime[3].size()||
                checkminute.size() != checkdateandtime[4].size()||
                checksecond.size() != checkdateandtime[5].size()){
                return "";
            }
        //cout << year<< '/' << month << '/' << day << ' ' << hour << ':' << minute << ':' << second << '\n';
        return dateandtime;     
}
string transaction (const char * SequenceNumber, const char * RetailStoreID, const char * WorkStationID, const char * BusinessDayDate, const char * BeginDateTime, const char * StartTransTime, const char * EndTransTime, const char * EndDateTime, const char * RawData){
    string output;
    string bdd, bdt, stt, ett, edt;
    bdd = dateFormatChecker(BusinessDayDate);
    bdt = dateandtimeFormatChecker(BeginDateTime);
    stt = dateandtimeFormatChecker(StartTransTime);
    ett = dateandtimeFormatChecker(EndTransTime);
    edt = dateandtimeFormatChecker(EndDateTime);
    cout << "<Transaction>" << "\n\t<RetailStoreID>"
         << RetailStoreID   << "</RetailStoreID>\n\t<WorkStationID>"
         << WorkStationID   << "</WorkStationID>\n\t<SequenceNumber>"
         << SequenceNumber  << "</SequenceNumber>\n\t<BusinessDayDate>"
         << bdd             << "</BusinessDayDate>\n\t<BeginDateTime>"
         << bdt             << "</BeginDateTime>\n\t<StartTransTime>"
         << stt             << "</StartTransTime>\n\t<EndTransTime>"
         << ett             << "</EndTransTime>\n\t<EndDateTime>"
         << edt             << "</EndDateTime>\n\t<RawData>"
         << RawData         << "</RawData>\n</Transaction>";
    output = _getch();
    return output; 
}
int main(void) {
  vector<string> words;
  char * data = "1,1,SAMPLE,2010-01-31,2011-01-31 14:09:10,2011-01-31 14:42:10,2011-01-31 14:42:10,2011-01-31 14:42:10,JELLY-O RUBBERB\n\r               13.25V.¶üÁËO";
  Split( data, ",", words );
  char SN[11], RSI[200], WSI[200], BDD[100], BDT[100], STT[100], ETT[100], EDT[100], RD[100];
  strcpy_s(SN, words[0].c_str());
  strcpy_s(RSI, words[1].c_str());
  strcpy_s(WSI, words[2].c_str()); 
  strcpy_s(BDD, words[3].c_str());
  strcpy_s(BDT, words[4].c_str());
  strcpy_s(STT, words[5].c_str());
  strcpy_s(ETT, words[6].c_str());
  strcpy_s(EDT, words[7].c_str());
  strcpy_s(RD, words[8].c_str());
  string PosData;
  PosData = transaction(SN,RSI,WSI,BDD,BDT,STT,ETT,EDT,RD);
/* Checker 
  for (int i = 0; i != words.size(); i++){
      cout << words[i] << nextline;
  }
    cout << SN << nextline << RSI << nextline << WSI << nextline << BDD << nextline << BDT << nextline << STT << nextline << ETT << nextline << EDT << nextline << RD; 
*/
return 0;
}

FSNPC.cpp

#include <iostream>
#include <sstream>
#include <vector>
#include <string>
#include <cstring>
#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
#include "FormatPosDataXml().cpp"
using namespace std;
string getstring(string holder){
    if (holder == "" || holder.size()>100){
        exit(1);
    }
    int i=0,ch=0;
    int size;
    char charInput[100];
        strcpy_s(charInput, holder.c_str());
        size = strlen(charInput);
        #define DATA_LENGTH 100
        #define BUFFER_LENGTH (DATA_LENGTH)
        char Buffer[BUFFER_LENGTH];
            while (i < DATA_LENGTH) {
                Buffer[i++] = charInput[i];
                Buffer[i] = '\0';
                if(size == i){
                        break;
                    }
            }
            holder = Buffer;
            strcpy_s(charInput, holder.c_str());
            size = strlen(charInput);
            i = 0;
            for(int j = 0;j<size;j++)
            {
                if (charInput[j] < 2) 
                {
                    if (charInput[j+i] > 2 && charInput[j+i] != 17){
                        charInput[j] = charInput[j+i];
                        charInput[j+i]='\0';
                        i=0;
                        }
                    else{
                        i++;
                        j--;
                    }
                }else if (charInput[j] == 17) 
                {
                    if (charInput[j+i] > 2 && charInput[j+i] != 17){
                        charInput[j] = charInput[j+i];
                        charInput[j+i]='\0';
                        i=0;
                        }
                    else{
                        i++;
                        j--;
                    }
                }
            }
            size = strlen(charInput);
            for(int remove = 0; remove<size ;remove++)
            {
                if (charInput[remove] < 2 || charInput[remove] == 17) 
                {
                    charInput[remove]='\0';
                }
            }
             string handler;
             handler = charInput;
             handler = handler.substr(0, handler.length() - 1);
             return (handler);
    }
/*
int main(void){
    string final;
    string input = "JELLY-O RUBBERB\n\r               13.25V.¶üÁË0";
    string input2 = "STIÁËCK-O CHOCO\n\r               10.52C.ÁË0¶ü";
    string input3 = "STICÁËK-O VANILLA\n\r               10.52C.ÁË0¶ü";
      final = getstring(input)+ "\n" +getstring(input2)+ "\n"
+getstring(input3);
        cout<<final;
        _getch();
    return 0;
}*/

keypress.cpp

#include <iostream>
#include <conio.h>
#include <stdio.h>
#include <string>
#include "FormatPosDataXml().cpp"
    using namespace std;
int c;
char temp[256];
    char getkeypress(char c){
        if (c==0x1b){
            exit(1);
         }
         else if (c==0||c==224)        
          {
                    c = _getch();
                    if (c==0x3b){
                        cout << "You typed: F1\n";
                    }
                    else if(c==0x3c){
                        cout << "You typed: F2\n";
                    }
                    else if(c==0x3d){
                        cout << "You typed: F3\n";
                    }
                    else if(c==0x3e){
                        cout << "You typed: F4\n";
                    }
                    else if(c==0x3f){
                        cout << "You typed: F5\n";
                    }
                    else if(c==0x40){
                        cout << "You typed: F6\n";
                    }
                    else if(c==0x41){
                        cout << "You typed: F7\n";
                    }
                    else if(c==0x42){
                        cout << "You typed: F8\n";
                    }
                    else if(c==0x43){
                        cout << "You typed: F9\n";
                    }
                    else if(c==0x44){
                        cout << "You typed: F10\n";
                    }
                    else if(c==133){
                        cout << "You typed: F11\n";
                    }
                    else if(c==134){
                        cout << "You typed: F12\n";
                    }
          }
          else
          { 
                while((cin.getline(temp, sizeof(temp), '\n'))&&(temp!="")){
                    cout << "You typed:" << temp << '\n';
                    break;
                }
          }
    }
/*  
int main(void){
    while (c^=0x1b){
            cout<<"Press any key:\n";
            c = getkeypress(_getch());
    } 
      _getch();
      return 0;
}
*/

how could I link all of these files. I want them to be a library. How could i do it then?

Solution 1

In general, it is bad practice to include another .cpp file inside of a .cpp file. The right way is to break out declarations into .h files and put the definitions in .cpp files. Make sure to put a bogus define at the top of each of your .h files to prevent accidental re-inclusion, as in:

#ifndef MYFILE_H_
#define MYFILE_H_
// your code goes here
#endif

When you compile your program, you need to compile all the .cpp files into .o files (or .obj on Windows), and then link them together. For example (Linux/Mac):

g++ -c foo.cpp
g++ -c bar.cpp
g++ foo.o bar.o -o theMainExecutable

Solution 2

You can't include .cpp files, you need to use .h files, which are definitions for functions. Define the stuff in the header files, then implement them (Write the code for them) in the .cpp files.

int main() can only go in one .cpp file, you need to put your code in a function, define it in a header, then include into your main file, then execute it in int main().

Solution 3

I haven't read all the code, but I would guess you are defining the same function in two modules. Firstly, you should not have a main in all three files. Only one of them. If you are planning to make a library, none of the files should have a main -- that should be in the program which imports your library.

As for convertInt, I suspect it is defined in multiple files. If it isn't, then perhaps it is defined in a header file. You should only put declarations in a header file, such as this:

string convertInt(int number);

(note the semicolon)

The definition should always appear in the corresponding CPP file, like this:

string convertInt(int number) { ... // Body of the function }

If the definition appears in the header file, you have a problem, because every CPP file which #includes that header will contain a duplicate definition.

Solution 4

Without weeding through your huge jumble of code, it seems that you are trying to merge different source files into the same project resulting in conflicting names.

I think you will just need to find a way to structure your code so that you don't get conflicting symbols. You obviously cannot have three different entry-points in your application. Which one do you want to be called? If you want the user to choose, for example, then you have to write the code for this, and name your functions accordingly.

For example with convertInt, if you need to include different variations of this function in your application, then you will need to name it properly to distinguish it.

Possible solutions for convertInt include:

1. Wrap convertInt (and possibly other functions) in a namespace, and call them like Variation1::convertInt(x)
2. Just give things unique names. convertInt1, convertInt2, etc.
3. Take the time to merge related functions. I doubt that two functions named convertInt, in the same project, with the same signature, actually do different things. Merge them so there is only 1 function to think about.

Apologies if my answer has nothing to do with your problem.

View more solutions

Comments

[mgiuca]

This code is way too hard to read. Perhaps you or someone else can format it better. Also you should not post complete code examples in a question. Try stripping it down to the bare minimum code required to generate the error.

[Dave O.]

Why do you want to include a cpp file into another one? What are you trying to accomplish (in abstract terms - don't think of code for now)?

[mgiuca]

Ah, having read Chris's answer, I see the problem: You are #including a CPP file, effectively causing it to be used as a header file.

[Andro Miguel M. Bondoc]

SO i need to put the codes of the other C++ files to the .h files?

[mgiuca]

@Andro See my answer. You should always have one .h file for every .cpp file. Functions should only go in .cpp files, never in .h files. Each public function in the .cpp file should have a declaration (the same heading, but with a semicolon instead of a body) in the corresponding .h file. You should always #include .h files from other modules, never .cpp files.

[Oystein]

Technically it is perfectly legal to #include whatever kind of file you want.

[Oystein]

Definitions may appear in headers as well, most commonly as inline.

[mgiuca]

@Øystein Sure it is, but a) it is against all conventions and established practice of the past 30 years, and b) it is quite illegal to import a file which contains any function definition in multiple modules of a project.

[tenfour]

@mgiuca inline functions (including templates) are extremely common in headers. In other words, "function body" is not the thing that distinguishes what should be in a .cpp vs .h, it's more about where the resulting code should be generated - inline or linked.

[mgiuca]

@Øystein Well, only as inline (it's the only way to avoid an error). I was trying to lay some initial ground rules for beginning C++, not explain all the quirks of the language.

[tenfour]

By "most commonly" I think you mean "always".

[mgiuca]

He's not trying to define different versions of convertInt. Rather, there is only one version, but it is being #included into all three files.

[Chris]

I'd guess he's coming from a language such as Lua or Blitz where include means copy and paste the contents of that file into the file you are in now.

[Oystein]

@mgiuca: Disagree with a) too, I use it, it's common for large aggregate-initialization lists.

[mgiuca]

@tenfour I am ignoring inline functions since this is a fairly basic mistake and it isn't helpful to go into all the exceptions -- better just to lay some initial ground rules. But yes, if you want to be technically correct, inline functions are an exception.

[Chris]

CPP uses a header system though, in good practice your 'final' file with everything included in it would have forward declarations, in Blitz at least (not completely sure about Lua) ALL of the code is imported into the 'final' file.

[mgiuca]

@Chris C/C++ #include does just copy and paste the contents of that file into the file you are in now. It's just different due to the linker. In Lua, for example, you do want to paste the entire contents of the file because the top-level module is not linked with the other ones later. In C/C++, you can't because you are going to separately link all the definition files later.

[Oystein]

@tenfour and mgiuca: No, I mean "most commonly". You write your whole program in a header and just include it in a .cpp file (or just compile the header, unless your compiler freaks out) if you wish.

[Chris]

@mgiuca That was kind of what I was getting at, you would have the declarations in your 'final' file and then link the implementation later.

[Fred Nurk]

@Øystein: "A #include directive shall identify a header or source file that can be processed by the implementation." [§16.2p1] You cannot just name any file.

[mgiuca]

@Øystein I think you are massively confusing the issue. First, it doesn't help to bring up all the possible special cases which you might use as an advanced user when the OP clearly has not gotten the fundamental concept of header files. Second, why would you ever write a program in a header file and include it in a .cpp file? It would break if you ever included it in multiple .cpp files and linked them. (Yes, inline is an exception, but it's the only exception.) Just because you can do something doesn't mean you should bring it up here, especially if it has no use ever.

[Fred Nurk]

_MYFILE_H_ is a reserved name; don't use it.

[Oystein]

@mgiuca: Knowledge does not hurt. Even though the OP won't have a use for it, you and tenfour should be happy at least :) And this does have its use, as I mentioned in a comment to another answer.

[Oystein]

@Fred: Huh? goes to get standard

[Oystein]

@Fred: You are right, it does say that. So the file must be processable by the implementation, I stand corrected. Then again, it does not make much sense to include a file that can not be processed.

[Fred Nurk]

@Øystein: I was also looking for a requirement that spelled out that a file must also not end with a partial line (missing a terminating newline), but I don't see it in the C++ standard; perhaps it's specified in C's.

[Oystein]

@Fred: It's in C++ too, see 2.1.1.2 - no newline => UB. What I really meant with my comment was of course that you could #include anything as long as the file contained valid C++ code.

[Fred Nurk]

@Øystein: And I was nitpicking it, of course, because it's just bad advice. Don't include .cpp files.

[Oystein]

@Fred: No problem with that, my whole role in this question so far has been nitpicking.

[mgiuca]

@Øystein Knowledge certainly can hurt. As someone who has taught this concept at university for the past five years, I know better than to offer students random advice, even if technically correct. If something can be done but shouldn't be with a handful of advanced exceptions, it is better to simply tell students not to do it, rather than say "sure you can do it" and then start a lengthy discussion about when and why. Students are then less likely to think it's okay. Even though, you can, I don't want to encourage people to go #including .cpp files or placing definitions in headers.

[Oystein]

@mgiuca: I never offered any advice to the OP. As a programmer I naturally react to inaccuracies, and prefer not to see false facts. I think part of what makes this community good is the pedantry going on here, and the attention that is payed to being succinct and accurate. It has taught me a lot.

[EmeryBerger]

Good point - changed. See stackoverflow.com/questions/228783/… for why.