Multiarch Cross-toolchains : "-rpath-link" mandatory ?

[Sébastien NOEL <sebastien@twolife.be>]

Hi,

After reading the "Debian's Google Summer of Code 2012 wrap-up"
on debian-devel-announce, i did want to test a Multiarch
Cross-toolchains, so i did rebuild gcc with patches
from http://emdebian.org/~thibg/patches/gcc-4.7/
and it almost works :-)

But i'm wondering if i did something wrong, because i can't
trivially link with other libs :(

~/trivial-test# cat 1.c
#include <stdio.h>
int main(void)
{
  printf("Hello world\n");
  return 0;
}

a simple "arm-linux-gnueabihf-gcc 1.c" works perfectly,
but...

# arm-linux-gnueabihf-gcc 1.c -lasound
/usr/lib/gcc/arm-linux-gnueabihf/4.7/../../../../arm-linux-gnueabihf/bin/ld: 
warning: libm.so.6, needed by 
/usr/lib/arm-linux-gnueabihf/libasound.so, not found (try using -rpath 
or -rpath-link)
/usr/lib/gcc/arm-linux-gnueabihf/4.7/../../../../arm-linux-gnueabihf/bin/ld: 
warning: libdl.so.2, needed by 
/usr/lib/arm-linux-gnueabihf/libasound.so, not found (try using -rpath 
or -rpath-link)
/usr/lib/gcc/arm-linux-gnueabihf/4.7/../../../../arm-linux-gnueabihf/bin/ld: 
warning: libpthread.so.0, needed by 
/usr/lib/arm-linux-gnueabihf/libasound.so, not found (try using -rpath 
or -rpath-link)
/usr/lib/gcc/arm-linux-gnueabihf/4.7/../../../../arm-linux-gnueabihf/bin/ld: 
warning: librt.so.1, needed by 
/usr/lib/arm-linux-gnueabihf/libasound.so, not found (try using -rpath 
or -rpath-link)
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`clock_gettime@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`log@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`pthread_join@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`fmod@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`ceil@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`rintf@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`floor@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`dladdr@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`pthread_mutex_trylock@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`sqrtf@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`exp@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`sqrt@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`pow@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`dlsym@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`dlclose@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`log10@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`pthread_create@GLIBC_2.4'
/usr/lib/arm-linux-gnueabihf/libasound.so: undefined reference to 
`dlopen@GLIBC_2.4'
collect2: error: ld returned 1 exit status

if i add 1) all the needed libs ; or 2) "-rpath-link"
it works.

# arm-linux-gnueabihf-gcc 1.c -lasound -lm -lpthread -ldl -lrt
# arm-linux-gnueabihf-gcc 1.c -lasound 
-Wl,-rpath-link=/lib/arm-linux-gnueabihf:/usr/lib/arm-linux-gnueabihf

so, my questions are:
- is it normal ?
- if it's the expected behavior, is there any environment variables
that need to be set to tell gcc where to find the libs ?
- did i miss something else ?

Thanks,

Sébastien