Re: libc.so GROUP Statement

[Doug Kehn <rdkehn@yahoo.com>]

Hi Yann,

--- On Tue, 12/29/09, Yann E. MORIN <yann.morin.1998@anciens.enib.fr> wrote:

> From: Yann E. MORIN <yann.morin.1998@anciens.enib.fr>
> Subject: Re: libc.so GROUP Statement
> To: crossgcc@sourceware.org
> Cc: "Doug Kehn" <rdkehn@yahoo.com>
> Date: Tuesday, December 29, 2009, 1:12 PM
> Hello Doug!
> Hello All!
> 
> On Tuesday 29 December 2009 18:28:10 Doug Kehn wrote:
> > I'm building arm-cortex_a8-linux-gnueabi with
> crosstool-ng-1.5.2.
> > The resulting libc.so contains: 
> > 
> > /* GNU ld script
> >    Use the shared library, but some
> functions are only in
> >    the static library, so try that
> secondarily.  */
> > OUTPUT_FORMAT(elf32-littlearm)
> > GROUP ( /lib/libc.so.6 /usr/lib/libc_nonshared.a 
> AS_NEEDED ( /lib/ld-linux.so.3 ) )
> 
> This is (should be!) black magic used by glibc, and is to
> be interpreted
> relative to the sysroot.
> 
> > Cross compiling some applications I receive the
> following error:
> > .../arm-cortex_a8-linux-gnueabi/bin/ld: cannot find
> /usr/lib/libc_nonshared.a
> > collect2: ld returned 1 exit status
> 
> How do you call your compiler? If you did set CT_PREFIX_DIR
> to (eg.):
>   /opt/toolchain
> 
> Then you call the compiler with :
>   /opt/toolchain/bin/arm-cortex_a8-linux-gnueabi-gcc
> 
> Ot you set PATH="${PATH}:/opt/toolchain/bin" and you call:
>   arm-cortex_a8-linux-gnueabi-gcc
> 
> Do *not* call gcc like that:
>   /opt/toolchain/arm-cortex_a8-linux-gnueabi/bin/gcc
> 

I use the PATH method: PATH=/opt/toolchain/bin:$PATH.  Then set CC=arm-cortex_a8-linux-gnueabi-gcc

> > If I manually change the GROUP statement in libc.so
> to:
> > GROUP ( libc.so.6 libc_nonshared.a  AS_NEEDED (
> ld-linux.so.3 ) )
> > the applications cross compile without error.
> 
> This is an error. As I said, the paths in GROUP are
> relative to the
> sysroot, and gcc should find them (if called as above).
> 
> > Am I doing something wrong when cross compiling the
> applications?
> > 
> > The arm-cortex_a8-linux-gnueabi crosstool.config has
> CT_USE_SYSROOT=y
> > (and CT_SYSROOT_DIR_PREFIX=""). I thought the path in
> the libc.so GROUP
> > statement would be pointing to the toolchain's sysroot
> directory.
> 
> Hehe! glibc's black magic. See:
>   http://www.gnu.org/software/libc/manual/html_node/Linux.html
> around the end of the page.
> 
> > I'm basing this on glibc.sh running make with
> install_root=$(CT_SYSROOT_DIR).
> > Am I not reading the script correctly?
> 
> Yes, that in the end is telling glibc to strip
> 'install_root' from the
> paths, so that when you move the toolchain around, the
> sysroot stuff
> continues to work. The toolchain is thus relocatable.
> 

Ah ... I was interpreting install_root as a prefix instead of a strip.  Thanks.

> > Is there a way to configure the toolchain to alter the
> paths in the
> > libc.so GROUP statement?
> 
> I never needed to do that, and most important, in my
> understanding, that
> would break glibc.
> 
> Please, confirm the way you are calling the compiler, and
> if you indeed
> call it the way I explained above, then we'll see for a
> proper fix.
> 

I'll keep investigating.

Thanks,
...doug





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