How do I link glibc's implementation of iconv?
The GNU C library provides an implementation of iconv - how do I use it?
Simple program:
#include <iconv.h>
int main( int argc, char **argv ) {
iconv_t cd = iconv_open( "UTF-8", "ISO-8859-1" );
iconv_close( cd );
return 0;
}
Compile and link:
$ gcc -Wall iconv.c -o iconv
/tmp/ccKAfXNg.o: In function `main':
iconv.c:(.text+0x19): undefined reference to `libiconv_open'
iconv.c:(.text+0x29): undefined reference to `libiconv_close'
collect2: ld returned 1 exit status
List the symbols to show they exist!
$ nm -D /lib/libc-2.12.1.so | grep iconv
00017920 T iconv
00017ae0 T iconv_close
00017720 T iconv_open
If I install the GNU libiconv library to /usr/local and link with -liconv it works. How do I link with the glibc implementation of iconv?
EDIT: More information as requested from the comments:
List all iconv.h files in /usr (1 match)
$ find /usr/ | grep "iconv\.h"
/usr/include/iconv.h
Reinstall libc6-dev to ensure the correct header is installed.
$ dpkg -S /usr/include/iconv.h
libc6-dev: /usr/include/iconv.h
$ apt-get install --reinstall libc6-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 0 not upgraded.
Need to get 0B/4,910kB of archives.
After this operation, 0B of additional disk space will be used.
(Reading database ... 143458 files and directories currently installed.)
Preparing to replace libc6-dev 2.12.1-0ubuntu10.1 (using .../libc6-dev_2.12.1-0ubuntu10.1_i386.deb) ...
Unpacking replacement libc6-dev ...
Setting up libc6-dev (2.12.1-0ubuntu10.1) ...
Compile and link again with suggested preprocessor option:
$ gcc -Wall -DLIBICONV_PLUG iconv.c -o iconv
/tmp/ccKAfXNg.o: In function `main':
iconv.c:(.text+0x19): undefined reference to `libiconv_open'
iconv.c:(.text+0x29): undefined reference to `libiconv_close'
collect2: ld returned 1 exit status
Output from gcc -H:
$ gcc -H iconv.c
. /usr/include/iconv.h
.. /usr/include/features.h
... /usr/include/bits/predefs.h
... /usr/include/sys/cdefs.h
.... /usr/include/bits/wordsize.h
... /usr/include/gnu/stubs.h
.... /usr/include/bits/wordsize.h
.... /usr/include/gnu/stubs-32.h
.. /usr/lib/gcc/i686-linux-gnu/4.4.5/include/stddef.h
Multiple include guards may be useful for:
/usr/include/bits/predefs.h
/usr/include/gnu/stubs-32.h
/usr/include/gnu/stubs.h
/usr/lib/gcc/i686-linux-gnu/4.4.5/include/stddef.h
pastbin copy of /usr/include/iconv.h
Fixed: Reboot fixed the issue. I suspect a cached copy of libiconv was causing the conflicts, even though it was deleted from disk.
Answer
Your program seems fine and compiles fine on my system (Mandriva Linux 2010.1).
I find the libiconv_* references in your compile log worrisome, though. Are you sure that the iconv.h version that gets included comes from glibc and not from a separate libiconv implementation, such as GNU libiconv? It sounds as if it adds a lib prefix to all iconv functions to avoid symbol collisions with the iconv implementation of the C library that came with the system.
Having to explicitly link to libiconv points to a separate iconv implementation too - glibc does not need it.
EDIT:
For the record, I just verified that using the iconv.h header file from libiconv without explicitly linking against it will produce exactly the result that you are seeing - it renames all iconv functions by adding a lib prefix to their names.