I happened to get that already defined in .obj error. This is structure of my project:
#include "main.h";
#include <iostream>
#include <string>
#include <sstream>
#include <boost/asio.hpp>
#include <boost/thread/thread.hpp>
#include "client.cpp"
#ifndef SOCKET_CLIENT_CLASS
#define SOCKET_CLIENT_CLASS
#ifndef BOOST_ASIO_HPP
#include <boost/asio.hpp>
#endif
/*CLASS DEFINITION HERE*/
#endif
This is what compiler is complaining about:
main.obj : error LNK2005: "public: bool __thiscall SocketClient::read(int,char *)" (?read@SocketClient@@QAE_NHPAD@Z) already defined in client.obj
Note it is complaining about my class, not boost. One interesting thing is, that when I remove #include <boost/asio.hpp>
from client.cpp, I get errors thouhg it is included in main.h too.
As you can see, I'm not double defining/including my class, its included exactly once in main.h. So what's going on here?
I have read this answer, but it was no help, since it expects double inclusions. Take this fact into osideration before voting for duplicate, because this simply means beheading me without mercy.
This question is related to
c++
visual-studio-2010
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This is one of the method to overcome this issue.
client.cpp
#ifndef SOCKET_CLIENT_CLASS
#define SOCKET_CLIENT_CLASS
#ifndef BOOST_ASIO_HPP
#include <boost/asio.hpp>
#endif
class SocketClient // Or whatever the name is... {
// ...
bool read(int, char*); // Or whatever the name is...
// ... };
#endif
client.h
bool SocketClient::read(int, char*)
{
// Implementation goes here...
}
main.cpp
#include <iostream>
#include <string>
#include <sstream>
#include <boost/asio.hpp>
#include <boost/thread/thread.hpp>
#include "client.h"
// ^^ Notice this!
main.h
int main()
You probably don't want to do this:
#include "client.cpp"
A *.cpp file will have been compiled by the compiler as part of your build. By including it in other files, it will be compiled again (and again!) in every file in which you include it.
Now here's the thing: You are guarding it with #ifndef SOCKET_CLIENT_CLASS
, however, each file that has #include "client.cpp"
is built independently and as such will find SOCKET_CLIENT_CLASS
not yet defined. Therefore it's contents will be included, not #ifdef'd out.
If it contains any definitions at all (rather than just declarations) then these definitions will be repeated in every file where it's included.
I do recomend doing it in 2 filles (.h .cpp)
But if u lazy just add inline
before the function
So it will look something like this
inline void functionX()
{ }
more about inline functions:
The inline functions are a C++ enhancement feature to increase the execution time of a program. Functions can be instructed to compiler to make them inline so that compiler can replace those function definition wherever those are being called. Compiler replaces the definition of inline functions at compile time instead of referring function definition at runtime. NOTE- This is just a suggestion to compiler to make the function inline, if function is big (in term of executable instruction etc) then, compiler can ignore the “inline” request and treat the function as normal function.
more info here
Source: Stackoverflow.com