Linker (ln) error: can't find certain files

Question

I'm building something from source and I get the following output while running make:

  ...
  CC     libpromises_la-mod_outputs.lo
  CC     libpromises_la-unix.lo
  CCLD   libpromises.la
  CC     cfknow.o
  CC     manual.o
  CCLD   cf-know
./.libs/libpromises.so: undefined reference to `dlerror'
./.libs/libpromises.so: undefined reference to `dladdr'
./.libs/libpromises.so: undefined reference to `dlclose'
./.libs/libpromises.so: undefined reference to `dlopen'
./.libs/libpromises.so: undefined reference to `dlsym'
collect2: ld returned 1 exit status
gmake[2]: *** [cf-know] Error 1
gmake[2]: Leaving directory `/tmp/cfengine/cfengine-3.1.5/src'
gmake[1]: *** [all] Error 2
gmake[1]: Leaving directory `/tmp/cfengine/cfengine-3.1.5/src'
gmake: *** [all-recursive] Error 1

I've googled a bit and it seems that the linker can't find certain files. I've never had to deal with something like this so I'm wondering if someone can help me decode this message and shed insight on WHICH file can't be found and how I can tell the linker where it is.

I know that the reference comes from libpromises.so, which is a binary file. Hence, opening it in vi only gives me garble. Am I supposed to be looking for libpromises.h? libpromises.c?

Answer 1

You should be able to edit the Makefile and accomplish this quickly.

NOTE - This assumes that the Makefile was made by GNU Autotools. According to the Cfengine tarball, they do.

First, open the Makefile and look for the flag LDFLAGS. It should look something like this:

LDFLAGS=-lfoo -lbar

Append to that listing -ldl. This adds a reference to the Dynamic Loading library.

Recompile, and the linker should be able to do it's job.

---

The LIBS environment variable is an environment variable that tells ./configure what extra libraries are needed, which it then sticks into the Makefile (so, to answer your question, ./configure doesn't actually run the linker - it makes the Makefile, which runs gcc with the parameters it got from ./configure).

So, use LIBS=-ldl && ./configure.