Re: [RFC] ld sysroot prefix handling

[Sven Rebhan <odinshorse at googlemail dot com>]

2009/5/27 Daniel Jacobowitz <drow@false.org>:
> You didn't say how you configured the linker, or how you invoked it,
> so it's hard to answer you.

As Mike said, in Gentoo the sysroot for cross-compile toolchains is
always set to /usr/$CTARGET.

So the settings are the following:

ld and gcc sysroot prefix:    /usr/armv4tl-softfloat-linux-gnueabi

test C program:                     /tmp/test.c
int main(void)
{
    return 0;
}

linker script:
/usr/armv4tl-softfloat-linux-gnueabi/usr/lib/libusb.so
/* GNU ld script
   Since Gentoo has critical dynamic libraries in /lib, and the static versions
   in /usr/lib, we need to have a "fake" dynamic lib in /usr/lib, otherwise we
   run into linking problems.  This "fake" dynamic lib is a linker script that
   redirects the linker to the real lib.  And yes, this works in the cross-
   compiling scenario as the sysroot-ed linker will prepend the real path.

   See bug http://bugs.gentoo.org/4411 for more info.
 */
OUTPUT_FORMAT ( elf32-littlearm )
GROUP ( /lib/libusb.so )

When compiling the test C program with:

armv4tl-softfloat-linux-gnueabi-gcc test.c

I get entry->sysrooted == TRUE and entry->filename == "/lib/libc.so.6" and the
program compiles.

When I try to do an

armv4tl-softfloat-linux-gnueabi-ld --verbose -T
/usr/armv4tl-softfloat-linux-gnueabi/usr/lib/libusb.so

I get entry->sysrooted == FALSE and entry->filename ==
"/lib/libusb.so" and the file is not found as libusb.so is not
installed on host but installed in
 /usr/armv4tl-softfloat-linux-gnueabi/lib/libusb.so.

> I believe that library search directories have the sysroot in their name
> field, but files initially don't. ?Then ldfile_open_file_search adds it.

The problem is _not_ the search path, but only the case where an
absolute path to a library is specified (as it is often done by
libtool for example). Btw, in the ldfile_open_file_search function,
the path is prepended to entry->filename IIRC and entry->sysrooted is
set to TRUE. So either you use the sysrooted field inconsistently or
libc should have /usr/armv4tl-softfloat-linux-gnueabi prepened. With
the change in the patch, both examples compile for me and fixes a
whole bunch of cross-compile problems...

> This script is only going to work if it's linked to from *inside* the
> sysroot. ?If it is, sysrooted should be TRUE already.
I dunno if it is relevant, but gentoo builds its packages in
/tmp/portage/$PACKAGENAME/work/PACKAGENAME in my case.

Best regards,

    Sven