Linking Libraries in C, unidentified reference

Question

I am trying to link a library to my c program so that my main program can use functions inside the library I am creating, however I am getting errors.

This is some of my library code (well call this file lib.c):

#include <bfd.h>
#include <stdio.h>

static void doDump ( bfd *abfd )
{
    printf (_("\n%s:     file format %s\n"), bfd_get_filename (abfd), abfd->xvec->name);
    doHeaders ( abfd );
}

This is my main program (well call this file main.c):

#include "bfd.h"

static void getFile ( char *filename, char *target )
{
    bfd *file;
    file = bfd_openr (filename, target);
    doDump (file);
    bfd_close (file);
}

int main (int argc, char **argv)
{
    char *target = NULL;
    bfd_init ();
    getFile ("a.out", target);
}

These are the commands I run to link the libraries:

cc -Wall -c lib.c

ar -cvq libdata.a lib.o

cc -o mainprog main.c lib.a -lbfd

However, I am getting this error:

undefined reference to doDump

Which is pointing to the line:

doDump (file);

What am I doing wrong?

Thanks

http://stackoverflow.com/a/558132/477878 – Joachim Isaksson Feb 12 '13 at 20:38 — Joachim Isaksson, Feb 12 '13 at 20:38

score 5 · Accepted Answer · answered Feb 12 '13 at 20:38

5

You have defined doDump in lib.c as static. This means it is invisible outside that file. Remove the static keyword and the problem should go away.

answered Feb 12 '13 at 20:38

lxop

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Wow, I totally missed that. Thanks – Pat Feb 12 '13 at 20:46
Also, the linker processes files in the order given, if something is defined but only used later, it won't be included (and thus give an error). Always place libraries last. – vonbrand Feb 19 '13 at 17:11

score 1 · Answer 2 · answered Feb 12 '13 at 20:39

Because you have declared doDump to be static it will not be "visible" in your main program. Remove the static qualifier and provide a valid declaration in your main.c (or some other header):

extern void doDump(bfd * file);

static void getFile ( char *filename, char *target )
{
    bfd *file;
    file = bfd_openr (filename, target);
    doDump (file);
    bfd_close (file);
}

Linking Libraries in C, unidentified reference

2 Answers2