Multiple Definition of <'variable/function'>

[bitsoglass]

I am trying to write a basic program with a candidate.h file, a candidate.cpp file, and a main.cpp file

I declared a function void readCandidates() in my candidate.h file.

I then define it in candidate.cpp as

void readCandidates ()
{
  cin >> nCandidates;
  string line;
  getline (cin, line);

  for (int i = 0; i < nCandidates; ++i)
    {
      getline (cin, candidateNames[i]);
      delegatesWon[i] = 0;
    }
}

The variables nCandidates, candidateNames[] and delegatesWon[] are all declared in candidate.h as well.

I also have

#ifndef CANDIDATE_H
#def CANDIDATE_H
...
#endif 

in my candidate.h file to ensure that it doesn't get defined twice.

When I run the command make main I get the error

/home/pmurray/cs250/Asst1/primaries.cpp:33: multiple definition of `candidate'
candidates.o:/home/pmurray/cs250/Asst1/candidates.cpp:8: first defined here
primaries.o: In function `assignDelegatesToCandidates()':
/home/pmurray/cs250/Asst1/primaries.cpp:37: multiple definition of `nCandidates'
candidates.o:/home/pmurray/cs250/Asst1/candidates.cpp:15: first defined here
primaries.o: In function `assignDelegatesToCandidates()':
/home/pmurray/cs250/Asst1/primaries.cpp:38: multiple definition of `delegatesWon'
candidates.o:/home/pmurray/cs250/Asst1/candidates.cpp:16: first defined here
candidates.o: In function `readCandidates()':

I tried putting extern before the declaration of one of the variables, and that resulted in the error

candidates.cpp:(.text+0x49): undefined reference to `candidateNames'
primaries.o: In function `findCandidate(std::basic_string<char, std::char_traits<char>, std::allocator<char> >)':
primaries.cpp:(.text+0x120): undefined reference to `candidateNames'
primaries.o: In function `printCandidateReport(int)':
primaries.cpp:(.text+0x1d8): undefined reference to `candidateNames' 

Anyone know what I am doing wrong?

[firedraco]

Sounds like you have some variables declared in your .h file. You'll need to define them in one cpp file, and then use extern in all other cpp files.

[bitsoglass]

so extern precedes the variable name everwhere? or just in candidate.cpp or main.cpp?

[firedraco]

extern should proceed the variable names in all .cpp files except for one of them (any of them are fine)

[ne555]

you could use extern in the .h