Gcc+binutils+libc cross-compiling: path to libc.so.6 malformed in "ld".

Kai Ruottu karuottu@mbnet.fi
Thu Aug 24 09:30:00 GMT 2006


Kaz Kylheku wrote:
> GCC is version 4.1.1
> Binutils 2.17
> Glibc is CVS head.
>
> When configuring gcc, I used --with-sysroot=/path/to/sysroot,
> where glibc is installed under usr/. The header files are
> found correctly.
>   
 What about the binutils, was the same '--with-sysroot='
given in their configure?

 Finding the headers happens with the built-in 'cpp' in the
'cc1', 'cc1plus' etc. real compilers, so only the GCC config
options will have any influence to this.

> When the linker is invoked, it is given
>
>   --sysroot=/path/to/sysroot.
>   
 Maybe this option is aimed for a 'ld' which was NOT configured
using the '--with-sysroot='...
> The linker resolves  -lc  to the absolute name
> /path/to/sysroot/usr/lib/libc.so.6. But then it catenates that
> to the sysroot, resulting in
>
>   /path/to/sysroot/path/to/sysroot/usr/lib/libc.so.6 which is nonsense.
>
> I can see using strace that it's actually trying to access that path.
> And so it dies with "cannot find /path/to/sysroot/lib/libc.so.6
> inside /path/to/sysroot".
>
> So, what's the /right/ way to coordinate the location of the
> target headers and libraries between gcc and binutils when
> cross-compiling?
>   
 My guess after seeing this "behaviour" would be to NOT use the
'--with-sysroot=' in the binutils configure with the newer binutils like
the '2.17'....  The GCC configured with it then giving that necessary
'--sysroot=/path/to/sysroot' to the linker. And the older GCCs which
didn't have the '--with-sysroot=' of course not giving that...

 Meanwhile any binutils configured using '--with-sysroot=', would add
the necessary 'offsets' automatically, so also the older GCCs could be
capable to use the 'sysroot'ed C library...

 I myself haven't used the '--with-sysroot=', only made symlinks like :

     $prefix/$target/include  ->  $sysroot/usr/include
     $prefix/$target/lib  ->  $sysroot/usr/lib

because the 'usr/lib' already has symlinks to '../../lib' for the majority
of its shared '.so' files, only symlinks to the '../../lib/libc.so.6' 
and to the
'../../ld-linux.so.2' (or '../../lib/ld.so.1' or something) must be manually
added just as editing the 'libc.so' script to not have any absolute paths
in its 'libc.so.6 libc_nonshared.a' or something GROUP row...  This has
been the "right" way for me because of using GCCs BEFORE the new
'--with-sysroot=' appeared, and still having those pre-gcc-3.3.3 or what
was the GCC version where this option appeared...  The Robert Heinlein's
"By-Law of Time": "If At Last You Do Succeed, Never Try Again", which
is so common among the most crosscompiler builders - they really seem
to build their crosscompilers only once, or if being obliged to do that
again, then starting everything from scratch again -  is not understood
by me :-(

 Using 5 or so GCC versions with the same $target binutils in $prefix/bin
and in $prefix/$target/bin, would cause me problems if trying to use the
'--with-sysroot'...  So things are easier with using only the idea, not 
really
using the full implementation...






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