I'm doing this using a sublime text editor and GNU Compiler....
And I have created this in these three file at the same hierarchical level. Still don't why it showing .....
c:/mingw/bin/../lib/gcc/mingw32/9.2.0/../../../../mingw32/bin/ld.exe C:\Users\BIVASH~1\AppData\Local\Temp\cc1guWsB.o:Class.cpp:(.text+0xc): undefined reference to `speak()'
c:/mingw/bin/../lib/gcc/mingw32/9.2.0/../../../../mingw32/bin/ld.exe: C:\Users\BIVASH~1\AppData\Local\Temp\cc1guWsB.o:Class.cpp:(.text+0x11): undefined reference to `jump()'
collect2.exe: error: ld returned 1 exit status```
Class .cpp
#include <iostream>
#include "Cat.h"
using namespace std;
int main()
{
speak();
jump();
return 0;
}
Cate.h
#ifndef CAT_H
#define CAT_H
void speak();
void jump();
#endif
Cat.cpp
#include <iostream>
#include "Cat.h"
using namespace std;
void speak(){
cout<<"mmmeeeeoooowwww!!!!";
}
void jump(){
cout<<"jump jump jump !!!!!";
}
When you want to use functions written on a different compilation unit, you have to link with the other unit's object file.
To do this, it's not sufficient to include the other unit's header, because it gives you only the declarations of the functions. In order to reach the definitions, you should compile both of the units together. For example, For foo.cpp and bar.cpp: g++ foo.cpp bar.cpp
In your case, just write:
g++ Class.cpp Cat.cpp
Related
This question already has answers here:
multiple definition error c++
(2 answers)
Closed 1 year ago.
I am getting error:
/usr/bin/ld: /tmp/ccCbt8ru.o: in function `some_function()':
Thing.cpp:(.text+0x0): multiple definition of `some_function()'; /tmp/ccc0uW5u.o:main.cpp:(.text+0x0): first defined here
collect2: error: ld returned 1 exit status
when building a program like this:
main.cpp
#include "common.hpp"
#include "Thing.hpp"
int main() {
some_function();
}
common.hpp
#pragma once
#include <iostream>
void some_function() {
std::cout << "something" << std::endl;
}
Thing.hpp
#pragma once
class Thing {
public:
void do_something();
};
Thing.cpp
#include "Thing.hpp"
#include "common.hpp"
void Thing::do_something() {
some_function();
}
I'm compiling with: g++ main.cpp Thing.cpp -o main.out
I've also tried using include guards instead of #pragma once, but it didn't seem to work either. Is there something I am forgetting here?
#pragma once and include guards can only prevent multiple definitions in a single translation unit (a .cpp file). The individual units know nothing about each other, and so cannot possibly remove the multiple definition. This is why when the linker links the object files, it sees the multiple definitions still.
To solve this issue, change common.hpp to:
#pragma once
void some_function();
This tells the compiler that there is some code for some_function.
Then, add a file common.cpp that contains the code for the common.hpp header:
#include "common.hpp"
#include <iostream>
void some_function() {
std::cout << "something" << std::endl;
}
Finally, change the g++ command to:
g++ main.cpp common.cpp Thing.cpp -o main
I am reading a book (C++ for dummies) as well as watching youtube videos to learn how to code. I am currently struggling with very simple class functions.
Main.cpp
#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <string>
#include "Test.h"
using namespace std;
int x;
int main(int nNumberofArgs, char* pszArgs[])
{
combat fight;
cout << x;
fight.dodmg();
cout << x;
return 0;
}
Test.h my header file with the class
#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <string>
using namespace std;
#ifndef TEST_H_INCLUDED
#define TEST_H_INCLUDED
class combat
{
public:
int dodmg();
void zero_out();
private:
int x;
};
#endif // TEST_H_INCLUDED
Test.cpp class functions
#include "Test.h"
int combat::dodmg()
{
x = x - 5;
return x;
}
void combat::zero_out()
{
x = 20
}
I tried to make this very simplistic just to figure out how to work a class.
I included a lot of #includes just to try and make sure it wasn't something stupid like I needed strings.
I am not sure why but the videos I watched simply had the header say
ifndef TEST_H (of their respective code, mine has an _INCLUDE as well, I tried deleting it and it still didn't work.
My unfortunate errors
on line 14 of main.cpp fight.dodmg(); it says
\Beginning_Programming-CPP\Playing_with_class\main.cpp|14|undefined reference to `combat::dodmg()'|
then below that
||error: ld returned 1 exit status|
How are you compiling this? I think this is an issue because you arent compiling your Test.cpp file. If you arent already, try compiling with the command:
g++ main.cpp Test.cpp -o MyProgram
UPDATE:
Few things, you dont have a closing statement to your #ifndef directive in Text.h, you will need a constructor to set the value of x so i added one to the combat class also you were missing a semicolon in the zero_out function. I added comments to all the lines I changed.
Okay try this:
Test.h
#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <string>
using namespace std;
#ifndef TEST_H_INCLUDED
#define TEST_H_INCLUDED
class combat
{
public:
combat(); // added constructor
int dodmg();
void zero_out();
private:
int x;
};
#endif // closed #ifndef
Text.cpp
#include "Test.h"
combat::combat() // implemented constructor
{
x = 20;
}
int combat::dodmg()
{
x = x - 5;
return x;
}
void combat::zero_out()
{
x = 20; // added ';'
}
Hope this helps,
Final edit: I dont think you really need your header guards in this scenario, you could remove the "#ifndef, #define, and the #endif" lines and not see a difference really
It sounds like you provide the wrong arguments for the compiler. Your header file (Test.h) simply provides signatures for the methods, but the implementations are given in the source file (Test.cpp).
This is an important part of writing C++ (or C) code. Your compiler does not automatically search for source files, so you need to tell it where to look, e.g.:
g++ -std=c++11 main.cpp Test.cpp -o main
This is a minimal program that I made to understand this problem better.
ADT.h
#ifndef ADT_H
#define ADT_H
class ADT {
public:
void print();
};
#endif
ADT.cpp
#include <iostream>
#include "ADT.h"
using namespace std;
void ADT::print()
{
cout << "This program works." << endl;
}
testADT.cpp
#include <iostream>
#include "ADT.h"
using namespace std;
int main(void)
{
ADT sa;
sa.print();
return 0;
}
I compiled it with the vim/minGW compiler my school provided me like so:
g++ testADT.cpp
Which produced the following error:
C:\Users\King\AppData\Local\Tempcc6eoWAP.o:testADT.cpp(.text+0x15 reference to 'ADT::print()'
collect2.exe error: ld returned 1 exit status
Can you explain this error message and indicate the error in my code?
You didn't post the error, but I see that you're missing the semicolon after void print()in the header.
EDIT: That's a linker error. Each source file should be compiled into an object file; then the object files linked:
g++ -c -oADT.o ADT.cpp
g++ -c -otestADT.o testADT.cpp
g++ -oADT ADT.o testADT.o
You can also do it in one line as in michaeltang's answer, but then you can't recompile the sources individually (the 2 step method scales better).
You should also compile ADT.cpp
g++ -o testadt testADT.cpp ADT.cpp
I m trying to compile this code and linking fails with the following error:
this is how i m compiling it;
g++ logtester.cc -I/home/foo/include -L/home/foo/lib -llog4cxx
/tmp/ccADKreY.o(.text+0x120): In function `main': undefined reference to `FrameworkLogger::getInstance()'
collect2: ld returned 1 exit status
Why? how can i fix it?
#include <log4cxx/logger.h>
#include <log4cxx/xml/domconfigurator.h>
using namespace log4cxx;
using namespace log4cxx::xml;
using namespace log4cxx::helpers;
class FrameworkLogger
{
private:
FrameworkLogger();
LoggerPtr logger;
public:
static LoggerPtr getInstance();
};
(Another file:)
#include "FrameworkLogger.h"
#include <iostream>
LoggerPtr FrameworkLogger::getInstance()
{
std::cout<<"test";
}
(Yet another file:)
#include "FrameworkLogger.h"
#include <iostream>
using namespace std;
int main(){
// LoggerPtr logger =
FrameworkLogger::getInstance();
std::cout<<"test";
}
This sounds like a linker error. Ensure that you are properly linking all of your object files
You need to list all compilation units (.cc files) in the compiler invocation:
g++ logtester.cc the-file-you-have-not-named.cc -I/home/foo/include -L/home/foo/lib -llog4cxx
I am working in c++ /ubuntu.
I have:
libr.hpp
#ifndef LIBR
#define LIBR
#include <string>
using namespace std;
class name
{
public:
name();
~name();
std::string my_name;
std::string method (std::string s);
};
#endif
and
libr.cpp
#include <iostream>
#include <string>
#include <stdlib.h>
#include "libr.hpp"
using namespace std;
name::name()
{
}
std::string name::method(std::string s)
{
return ("YOUR NAME IS: "+s);
}
From these two I've created a libr.a.
In test.cpp:
#include <iostream>
#include <string>
#include <stdlib.h>
#include "libr.hpp"
using namespace std;
int main()
{
name *n = new name();
n->my_name="jack";
cout<<n->method(n->my_name)<<endl;
return 0;
}
I compile with g++ and libr.a. I have an error: "name::name() undefined reference", why?
I would like to mention that I've added in qt creator at qmake the .a. When I compile, I have the error. How can I solve it?
This is a linker error, not a compiler error. It means that you have called but you have not defined the constructor. Your allocation name *n = new name(); calls the constructor.
Since you defined the constructor in your libr.cpp, what this means is that this compilation unit is not making its way into your executable. You mentioned that you are compiling with libr.a. When you compile your libr.cpp the result is a .o file, not a .a file.
You are not linking libr.o into your executable.
What are the steps you're using to compile your "project"?
I performed the following steps and managed to build it with warnings/errors.
g++ -Wall -c libr.cpp
ar -cvq libr.a libr.o
g++ -Wall -o libr main.cpp libr.a
One last thing, if I change the order off the last command, like
g++ -Wall -o libr libr.a main.cpp
I get the following error:
Undefined first referenced
symbol in file
name::name() /tmp/cc4Ro1ZM.o
name::method(std::basic_string<char, std::char_traits<char>, std::allocator<char
> >)/tmp/cc4Ro1ZM.o
ld: fatal: Symbol referencing errors. No output written to libr
collect2: ld returned 1 exit status
in fact ， you needn't define the destructor yourself because the default destructor will be used when the class calling is over.
and in the VS2008，it's all right！