I am getting linking error in the following program.
//FILE: CDummyMessage.h
#idndef DUMMY_FILE
#define DUMMY_FILE
#include "stdafx.h"
class CDummyMessage(){
static int objCount1;
std::string;
};
#endif //DUMMY_FILE
// CDummyMessage.cpp
all the necessary definition
//main cpp file: SmartPointerExample.cpp
#include "stdafx.h"
#include "CDummyMessage.h"
int main(){
CDummyMessage* OBJ1= new CDummyMessage();
}
I am getting this linking error:-
Error 1 error LNK2005: "private: static int dummy::CDummyMessage::ObjCount1" (?ObjCount1#CDummyMessage#dummy##0HA) already defined in DummyMessage.obj C:\Users\Veil\Documents\Visual Studio 2012\Projects\SmartPointerExample\SmartPointerExample\SmartPointerExample.obj
I am not able to figure out the reason of this linking error. I have made use of #ifndef directive that prevents duplicate inclusion of header file.
I think you have another file called CDummyMessage.cpp in your project ? and Visual studio Compiled that one too.
Related
I am using visual studio and #pragma once is not working. This is the following error i get:
1>namespaces.obj : error LNK2005: "int a" (?a##3HA) already defined in another.obj
1>fatal error LNK1169: one or more multiply defined symbols found
These are the files
main.cpp
#include <iostream>
#include "Header.h"
int main()
{
std::cout << a;
}
another.cpp
#include <iostream>
#include "Header.h"
void hi() {
std::cout << a;
}
header.h
#pragma once
int a = 5;
#pragma once does not mean "include me in only one source file", it means "only include me once in a single source file.
You should not define a global variable in a header file for exactly this reason. #pragma once does not protect you from this kind of error. In fact, nothing can protect you from this kind of error, because each source file is compiled separately. What happens in one compilation unit has no effect on what happens in another compilation unit.
The solution is to move int a = 5; to main.cpp, and change header.h to say extern int a;.
Ok so, simply said : I've included a .h into another .h and i get a compilation error telling me that the functions are already defined in main.obj
But, well i've only included Graphics.h one time so how can it be possible that main.obj also defined the Graphics.h functions ?
I got an Error LNK2005 "Already defined in main.obj".
Graphics.h contain functions that many others files will need, but for the moment we have a problem with just one file so I'd like to fix that first.
EDIT : SOLVED by spliting the header, i kept the header for the functions prototypes and I created a new Graphics.cpp for the functions definition
Here are the most concerned files, I've commented the files content so it is readable.
If I'm wrong by commenting please tell me and I'll put it on pastebin or something like that
main.cpp
#include "main.h"
using namespace std;
int main()
{
sMainData data = {};
main_Initialize(data);
while (data.config.window.isOpen())
{
main_Event(data);
main_Update(data);
main_Draw(data);
}
return 0;
}
main.h file :
#ifndef MAIN_H
#define MAIN_H
#include <SFML/Graphics.hpp>
#include "PlayerClass.h"
// Structures...
// Prototypes...
// Functions...
#endif // !MAIN_H
PlayerClass.h file :
#ifndef PLAYERCLASS_H
#define PLAYERCLASS_H
#include "AliveClass.h" // Including the mother
#include <SFML/Graphics.hpp>
#include <iostream>
#include <string>
#include "Graphics.h" // <-- So here we have our man
//Class definition
#endif // !1
Graphics.h file :
#ifndef GRAPHICS_H
#define GRAPHICS_H
#include "SFML/Graphics.hpp"
// Prototypes...
// Functions...
#endif // !GRAPHICS_H
You didn't provide a minimal reproducible example, but my best guess is, you have some function implemented in the header file, while ending up including that header, either directly or indirectly, in more than one cpp file. The result is exactly the same function with exactly the same signature, being compiled in both cpp files, which causes the linker to complain.
Solutions:
Move the function out of the header and into its own cpp file (probably the best)
Find a way to only include the header in one single cpp file (probably the second best in case the header isnt yours and you don't want to touch it)
Make that function inline (probably the easiest, but technically the worst)
The following code structure:
ArrayStack.h
#ifndef ARRAY_STACK_H
#define ARRAY_STACK_H
#include "Array.h"
// class ArrayStack
#endif
ArrayStack.cpp
#include "ArrayStack.h"
// ArrayStack's methods
Array.h
#ifndef ARRAY_HEADER
#define ARRAY_HEADER
#include <iostream>
// class Array
#endif
Array.cpp
#include "Array.h"
// Array's methods
main.cpp
#include "ArrayStack.h"
int main() {
return 0;
}
generates these errors:
LNK1169 one or more multiply defined symbols found
LNK2005 _main already defined in Array.obj
What's the problem here? Please do note that Array.cpp did have int main() defined in itself when it was included in the project for the first time, but no longer has it (neither does the ArrayStack.cpp). Also, the code compiles just fine when the int main() in main.cpp is omitted...
The error message means that in all the compiled code, the *.obj files, the linker finds more than one main() function. One is obviously in main.cpp.
The first solution that comes to mind, as mentioned in comments, is to (enforce) re-compile by somehow deleting the *.obj files.
When this doesn't change anything try to rebuild your solution separately from scratch. Start with main.cpp without the include. Then successively add files where you are confident that you won't get errors. Maybe you have to comment out some lines in some cases to make compilation possible.
I am having some trouble with the implementation of a constructor and I cannot figure out what is the problem. I have spent a lot of time with this problem: it would be grateful some kind of advice.
The main code is:
#include "stdafx.h"
#include "Rocket.h"
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
Rocket* rocket;
rocket=new Rocket();
//LLA* position=rocket->positionLLA;
return 0;
}
Rocket.h
#pragma once
#include "LLA.h"
class Rocket {
public:
Rocket(); // Default constructor
LLA* positionLLA;
};
Rocket.cpp
#include "stdafx.h"
#include "Rocket.h"
#include <iostream>
using namespace std;
Rocket::Rocket() // Default constructor
{
// Initialise the position
positionLLA=new LLA();
}
The error says:
error LNK2019: unresolved external symbol "public: __thiscall Rocket::Rocket(void)" (??0Rocket##QAE#XZ) referenced in function _main.
I know the error has something to do with not having declared a variable, but I think I have declared all classes and constructors.
PS: I am using Visual Studio 2008 in order to add dependencies.
I am assuming LLA is correctly defined in your .h file
Are you compiling Rocket.cpp into Rocket.o and main.cpp into main.o and then linking the two object files together?
Your error seems to imply that the linker cannot obtain symbol information from Rocket.o, which usually means Rocket.o was not found
Oh, as a detail, since Rocket is using an LLA*, you don't need to include LLA.h in Rocket.h, you can simply forward-declare
class LLA;
You might want to add #ifndef, #define, and #endif to your header files. Having multiple includes of the same thing in different files can lead to complications.
//head.h//
extern int sum(int,int);
//head.cpp//
#include "head.h"
#include "stdafx.h"
int sum(int x, int y)
{
return (x+y);
}
//mainfn.cpp//
#include "head.h"
#include "stdafx.h"
#include string
#include iostream
#include stdio.h
using std::string;
using std::cout;
using namespace System;
int main()
{
int x=10,y=2;
printf("value: %d",sum(x,y));
Console::ReadLine();
return 0;
}
While buliding in Visual studio 2005, this vc++ project is giving following error:
error C3861: 'sum': identifier not found.
Can anybody help me out with this?
You need to place the inclusion of head.h after stdafx.h. When precompiled headers are enabled the compiler will ignore the contents of all includes that occur prior to (in this case) the inclusion of stdafx.h .
Either remove stdafx.h from the project, and turn of precompiled headers.. or try moving head.h to be included after stdafx.h instead of before.