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！
Related
I already searched and found a solution for this problem but i find this a little bit strange. Anyway my problem is this:
Personal.h
class Personal
{
public:
Personal();
int money;
~Personal();
}
Personal.cpp
#include "Personal.h"
Personal::Personal()
{
money = 1800;
}
Personal::~Personal(){};
Now i want to compile in main
main.cpp
#include "Personal.h"
#include <iostream>
#include <vector>
int main()
{
std::vector<Personal> test(100);
}
When I write: g++ -Wall main.cpp -o main it gives me :
undefine reference to Personal::Personal()
undefine reference to Personal::~Personal()
The solution:
g++ -Wall Personal.cpp main.cpp -o main
Why do i need compile the Personal.cpp too?
Or the other main version is to include instead of "Personal.h", "Personal.cpp"
main.cpp
#include "Personal.cpp"
#include <iostream>
#include <vector>
Then the normal g++ -Wall main.cpp -o main works
Can someone help me?
Why do i need compile the Personal.cpp too?
Because you use functions that are defined in that file. In particular, you use the functions Personal::Personal and Personal::~Personal.
Can someone help me?
Make sure that all functions (that are odr-used) are defined in exactly one (or in all files, in case of inline functions) of the source files that you compile and link together.
I am a novice programmer in c++, and I am currently getting a compiling error
Undefined symbols for architecture x86_64
Supposedly this originates from how the header files and implementation files are included/coded.
Below is some code that generates the compiling error I am receiving
Main
//Main.cpp
#include <iostream>
#include <string>
#include "Animal.hpp"
using namespace std;
int main(){
Animal myPet;
myPet.shout();
return 0;
}
Header
//Animal.hpp
#ifndef H_Animal
#define H_Animal
using namespace std;
#include <string>
class Animal{
public:
Animal();
void shout();
private:
string roar;
};
#endif
Implementation
//Animal.cpp
#include "Animal.hpp"
#include <string>
Animal::Animal(){
roar = "...";
}
void Animal::shout(){
roar = "ROAR";
cout << roar;
}
This code generates my compiling issue. How would this issue be resolved?
Thanks for your time
EDIT
Undefined symbols for architecture x86_64:
"Animal::shout()", referenced from:
_main in test-5f7f84.o
"Animal::Animal()", referenced from:
_main in test-5f7f84.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
maybe you might want to see an alternative set of your 3 files, where things are a little more "sorted", you know, where things are put at places where they "really" belong to.
So here's the "new" header file ..
//Animal.hpp
#ifndef H_Animal
#define H_Animal
#include <string> // suffices
// Interface.
class Animal {
std::string roar; // private
public:
Animal();
void shout();
};
#endif
then the source file ..
//Animal.cpp
#include "Animal.hpp"
#include <iostream> // suffices
// Constructor.
Animal::Animal()
:
roar("...") // data member initializer
{}
// Member function.
void Animal::shout() {
roar = "ROAR";
std::cout << roar;
}
and the main program ..
//Main.cpp
#include "Animal.hpp"
int main(){
Animal thePet;
thePet.shout(); // outputs: `ROAR'
}
plus a little GNU makefile ..
all: default run
default: Animal.cpp Main.cpp
g++ -o Main.exe Animal.cpp Main.cpp
run:
./Main.exe
clean:
$(RM) *.o *.exe
Kick-off things typing just "make" in your cmd-line. Did you like it? --
Regards, M.
I can only find one error in your code and your compiler should have told you that one.
In Animal.cpp, you are using std::cout but you're not #includeing <iostream>. You #include it in Main.cpp but it is not needed there.
If you (really) want to refer to std::cout as cout in Animal.cpp, you also have to add a using namespace std directive in that file.
The using directive in the header file (Animal.hpp) is evil. Get rid of it and type std::string instead. Putting using directives into headers litters the namespaces of all files that use it.
I also don't understand your intentions with the roar member. What is the point of assigning "..." to it in the constructor and re-assigning "ROAR" to it every time shout is called? Couldn't you do without that variable and simply have
void
Animal::shout()
{
std::cout << "ROAR\n";
}
? I have added a newline because you'd probably want one.
The main issue I was having with this coding project was solved by #JamesMoore.
"#Nicholas Hayden Okay if you have three files, test.cpp(which has main), animal.cpp, and animal.hpp. The command should be g++ animal.cpp test.cpp. You need to compile all source files."
I am currently not using an IDE. So, when I was calling the compiler to compile my main.cpp - It was an issue of compiling the implementation file.
g++ test.cpp
needed to become
g++ test.cpp animal.cpp
This would call the compiler to compile everything the program needed.
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
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
What is an undefined reference/unresolved external symbol error and how do I fix it?
I have main.cpp:
#include "censorship_dec.h"
using namespace std;
int main () {
censorship();
return 0;
}
this is my censorship_dec.h:
#include <iostream>
#include <stdio.h>
#include <string.h>
using namespace std;
void censorship();
this is my censorship_mng.cpp:
#include "censorship_dec.h"
using namespace std;
void censorship()
{
cout << "bla bla bla" << endl;
}
I tried to run these files in SSH (Linux), so I wrote: make main, but I got:
g++ main.cpp -o main
/tmp/ccULJJMO.o: In function `main':
main.cpp:(.text+0x71): undefined reference to `censorship()'
collect2: ld returned 1 exit status
make: *** [main] Error 1
please help!
You have to specify the file where censorship is defined.
g++ main.cpp censorship_mng.cpp -o main
You must add censorship_mng.cpp in your compilation command:
g++ main.cpp censorship_mng.cpp -o main
Another solution (if you really don't want change your compile command) is making void censorship(); to a inline function and move it from .cpp to .h.
censorship_dec.h:
#include <iostream>
#include <stdio.h>
#include <string.h>
using namespace std;
inline void censorship()
{
// your code
}
And remove void censorship() from censorship_mng.cpp file.
once your project starts using several source-files to be compiled into a single binary, manual compilations become tedious.
this is usually the time when you start using a build-system, such as a Makefile
a very simple Makefile that uses default build-rules could look like
default: main
# these flags are here only for illustration purposes
CPPFLAGS=-I/usr/include
CFLAGS=-g -O3
CXXFLAGS=-g -O3
LDFLAGS=-lm
# objects (.o files) will be compiled automatically from matching .c and .cpp files
OBJECTS=bar.o bla.o foo.o main.o
# application "main" build-depends on all the objects (and linksthem together)
main: $(OBJECTS)
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