Question

I am getting below error. I can not understnad where does it happening? Whre it is going wrong.
I am developing some code as,

abc.h

#include<vector>
vector<string> vect;
vector<string>::iterator ab;

def.c

#include "abc.h"

    vect.push_back("a");
    vect.push_back("b");
    for(ab = vect.begin(); ab != vect.end(); ab++)
    {
    if(*ab == "b")
    {
    FIle *file->fun();
    }

abc.c

#include "abc.h"

    File::file()
    {
    vect.insert(1, "Something");
    }

I am getting an error as

"class std::_Vector_iterator<class std::_Vector_val<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,class std::allocator<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > > > testCase" (?testCase@@3V?$_Vector_iterator@V?$_Vector_val@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@V?$allocator@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@2@@std@@@std@@A) already defined in abc.obj
1>GTestThread.obj : error LNK2005: "class std::vector<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,class std::allocator<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > > vect" (?vect@@3V?$vector@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@V?$allocator@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@2@@std@@A) already defined in abc.obj
1>D:/ fatal error LNK1169: one or more multiply defined symbols found

Answer 1

This:

vector<string> vect;
vector<string>::iterator ab;

is a definition in a header, meaning the you’ll break the one definition rule when you include the header in multiple translation units. Change it to:

//abc.h
extern vector<string> vect;
extern vector<string>::iterator ab;

to make it a declaration and move the definition in a single implementation file:

//abc.c
#include "abc.h"
vector<string> vect;
vector<string>::iterator ab;

I’m still wondering how your def.c compiles, you can’t just paste statements in an implementation file outside a context.

Also, C++ has extensions .cc or .cpp (others too I think), not .c.