Hello

Outline of the problem:
Files:
1. a.cpp, a.h, atest.cpp
2. b.cpp, b.h

- file a.cpp is compiled to liba.so
- file b.cpp is compiled to libb.so
- function af01 defined in a.cpp calls the function bf01 defined in b.cpp
- file atest.cpp is compiled to executable program, which calls the af01 function therefore it calls indirectly the bf01 function

During atest.cpp compilation a compiler claims that:
mormegil@devel-1:/vol/cuma/sandbox$ g++ -Wall -L/vol/cuma/sandbox atest.cpp -la -o atest
/vol/cuma/sandbox/liba.so: undefined reference to `bf01(int)'

What is the way of correct compilation of liba.so ?

Up until now I did it in the following manner :

mormegil@devel-1:/vol/cuma/sandbox$ g++ -Wall -fPIC -c a.cpp
mormegil@devel-1:/vol/cuma/sandbox$ g++ -shared -W1,-soname,liba.so.1 -o liba.so.1.0 a.o -L/vol/cuma/sandbox/ -lb
mormegil@devel-1:/vol/cuma/sandbox$ ln -sf /vol/cuma/sandbox/liba.so.1.0 /vol/cuma/sandbox/liba.so
mormegil@devel-1:/vol/cuma/sandbox$ ln -sf /vol/cuma/sandbox/liba.so.1.0 /vol/cuma/sandbox/liba.so.1
and finally :
mormegil@devel-1:/vol/cuma/sandbox$ g++ -Wall -L/vol/cuma/sandbox atest.cpp -la -o atest

If the function af01 doesn't call the bf01 from libb.so the atest compiles and works well.

Best regards

Cuma

You have to also add the libb.so to the compilation of atest. Use the following command line to compile atest:
g++ -Wall -L/vol/cuma/sandbox atest.cpp -la -lb -o atest

Notice the addition of -lb

Dear Mike

Unfortunately it doesn't work giving the same error:
/vol/cuma/sandbox/liba.so: undefined reference to `bf01(int)'

In the first, I have built the libb.so:

g++ -Wall -fPIC -c b.cpp
g++ -shared -W1,-soname,libb.so.1 -o libb.so.1.0 b.o
ln -sf /vol/cuma/sandbox/libb.so.1.0 /vol/cuma/sandbox/libb.so
ln -sf /vol/cuma/sandbox/libb.so.1.0 /vol/cuma/sandbox/libb.so.1

In the second step, the liba.so

g++ -Wall -fPIC -c a.cpp
g++ -shared -W1,-soname,liba.so.1 -o liba.so.1.0 a.o -L/vol/cuma/sandbox -lb
ln -sf /vol/cuma/sandbox/liba.so.1.0 /vol/cuma/sandbox/liba.so
ln -sf /vol/cuma/sandbox/liba.so.1.0 /vol/cuma/sandbox/liba.so.1

At the end, the atest
g++ -Wall -L/vol/cuma/sandbox atest.cpp -la -lb -o atest

Maybe something wrong is with the sources:
____________________________
/* File: b.h */
#include <sys/types.h>
#include <string>

using namespace std;

// declaration
string bf01(int);

_____________________________
/* File: b.cpp */
/* libb source */

#include <iostream>
#include <sys/types.h>
#include <string>
#include "b.h"

using namespace std;

// definicja funkcj
string bf01(unsigned int a) {
if (a<3) {
a=3;
}
string s = "x";
string t = "y";
unsigned int i;
for(i=1;i<a;++i) {
s.append(t);
}
return s;
}
______________________________
/* File: a.h */
#include <sys/types.h>
#include <string>
#include "b.h"

using namespace std;

// declaration funkcji
int af01(string);

______________________________
/* File: a.cpp */
/* liba source */

#include <iostream>
#include <sys/types.h>
#include <string>
#include "a.h"
#include "b.h"

using namespace std;

int af01(string str1) {

int i=3;
string b;
b = bf01(i); // call to libb
b = b + str1;
return 0;
}
________________________________
/* File: atest.cpp */
#include <stdio.h>
#include "a.h"

using namespace std;

int main(int argc, char **argv) {

if (argc != 2) {
char err_msg[] = "error";
puts(err_msg);
return 1;
}
else {
af01(argv[1]); // call to liba
return 0;
}
}

Why don't you just put both *.cpp files in the same *.so?

In the task I have been given I have a complex shared library and I develop my own small shared library which uses the function of the first one. I can't compile program which use my library because the I have unresolved references to the functions of the first mentioned library.
So I have built two very simple libraries in order to learn the problem.

Cuma

Your prototype for bf01:

string bf01(int);

Does not match your definition:

string bf01(unsigned int a) {

Matching the two should solve your problem.

Your prototype for bf01:

string bf01(int);

Does not match your definition:

string bf01(unsigned int a) {

Matching the two should solve your problem.

Hello

Thank you very much! After correction the header file b.h I have found that the proper chain of compilation is:
g++ -Wall -fPIC -c a.cpp
g++ -shared -Wl,-soname,liba.so.1 -L/vol/cuma/sandbox -lb -o liba.so.1.0 a.o
ln -sf /vol/cuma/sandbox/liba.so.1.0 /vol/cuma/sandbox/liba.so
ln -sf /vol/cuma/sandbox/liba.so.1.0 /vol/cuma/sandbox/liba.so.1

g++ -Wall -L/vol/cuma/sandbox -la atest.cpp -o atest

Best regards

Cuma

This article has been dead for over six months. Start a new discussion instead.