From: "Iñaki Baz Castillo" <ibc@...>
Date: 2011-02-06T04:56:38+09:00
Subject: C extension: R_X86_64_32 problem when inlcuding a xxxxx.a library (64 bits SO)

Hi, I must include a header (udns.h) and library (libudns.a) in a Ruby
C extension (Linux 64 bits).

In extconf.rb I set:

  have_library("udns")

"ruby extconf" creates the Makefile:
--------------------------------
checking for main() in -ludns... yes
creating Makefile
--------------------------------

but "make" command fails:
-------------------------------
gcc -I. -I/usr/include/ruby-1.9.1/x86_64-linux
-I/usr/include/ruby-1.9.1/ruby/backward -I/usr/include/ruby-1.9.1 -I.
 -fPIC -fno-strict-aliasing -g -g -O2 -fPIC  -o em_udns.o -c em_udns.c
gcc -shared -o em_udns.so em_udns.o -L. -L/usr/lib -L.  -rdynamic
-Wl,-export-dynamic   -lruby-1.9.1 -ludns  -lpthread -lrt -ldl -lcrypt
-lm   -lc
/usr/bin/ld: ./libudns.a(udns_resolver.o): relocation R_X86_64_32
against `dns_defctx' can not be used when making a shared object;
recompile with -fPIC
./libudns.a: could not read symbols: Bad value
collect2: ld returned 1 exit status
-------------------------------

I know that "relocation R_X86_64_32" issue occurs with some libraries
in 64 bits and -fPIC is required. However AFAIK the above gcc command
does include -fPIC, am I right?

Anyhow, I can compile a pure C file (no Ruby) in a folder with these files:
- play1.c
- udns.h
- libudns.a
by running:   gcc play1.c -L. -ludns libudns.a -o play1

And the resulting "play1" executable works ok.


libudns.a has been compiled with library provided "configure", and its
Makefile does contain -fPIC option:
-------------------------------------------------
PICFLAGS = -fPIC
[..]
.c.lo:
        $(CC) $(CFLAGS) $(PICFLAGS) $(CDEFS) -o $@ -c $<
-------------------------------------------------


I'm a bit lost here, any help please?

-- 
Iñaki Baz Castillo
<ibc@aliax.net>