Error: undefined reference to `censorship()'

Question

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!

or use something like `g++ main.cpp censorship_mng.cpp -o main` — stijn, Jan 15 '13 at 11:37
try linking in *all* your compiled source files. Your compilation line only lists one: main.cpp — WhozCraig, Jan 15 '13 at 11:37
@someone_smiley, is there an option how to fix it without changing the name of the file? the lecturer wants us to send the exercise with these names. thank you! — Maor Cohen, Jan 15 '13 at 11:38
not sure if u can compromise on having definition of censorship() move to .h instead? — someone_ smiley, Jan 15 '13 at 11:43
why the f*** do you have `using namespace std;` in every single file? It's only needed where you use `cout` and `endl`. — stefan, Jan 15 '13 at 11:46

score 5 · Accepted Answer · answered Jan 15 '13 at 11:37

5

You have to specify the file where censorship is defined.

g++ main.cpp censorship_mng.cpp -o main

answered Jan 15 '13 at 11:37

yiding

3,482
18
17

in my function of censorship, I have another callings to another functions. so I got: /tmp/ccBpBk4A.o: In function `censorship()': censorship_mng.cpp:(.text+0x112): undefined reference to `read_files(char*, char*)' censorship_mng.cpp:(.text+0x129): undefined reference to `make_string(int&, char*, char (*) [21])' censorship_mng.cpp:(.text+0x139): undefined reference to `read_files(char*, char*)' censorship_mng.cpp:(.text+0x150): undefined reference to `make_string(int&, char*, char (*) [21])' collect2: ld returned 1 exit status – Maor Cohen Jan 15 '13 at 11:41
1

You need to add the files those symbols are defined in too. – yiding Jan 15 '13 at 11:42

masoud · Answer 2 · 2013-01-15T11:45:38.480

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.

score 0 · Answer 3 · answered Jan 15 '13 at 11:49

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)

Error: undefined reference to `censorship()'

3 Answers3