Re: Use of objcopy prevents prelink to work on Linux

From: Markus Schöpflin (markus.schoepflin_at_[hidden])
Date: 2005-07-14 11:25:13

Rene Rivera wrote:

> Markus Schöpflin wrote:
> 
>>I just discovered that I cannot prelink a dynamic library produced by bbv1. 
>>The system I tried this on was RHEL 3. The error message I got was:
>>
>>prelink: ... section file offsets not monotonically increasing
>>
>>After a lot of head scratching, I decided to disable the use of objcopy in 
>>gcc-tools.jam, et voila, now prelink works.
>>
>>This leaves me wondering why objcopy is used at all. I found some reference 
>>on this ML to a linker performance problem that this should fix, but I 
>>wasn't successful in digging up more info.

[snip explanation]

>>Is objcopy still needed?

> It may be that the "bug" in the linker is no longer there, and I 
> remember some discussion on the binutils crowd about it getting 
> addressed. So it's possible it's no longer needed. But that would apply 
> to new distributions as old one would still use the slower binutils.

The distro used is RHEL3, rpm -q binutils gives binutils-2.14.90.0.4-35.

>>I don't seem to get any noticable speed benefit 
>>when it's used.

> Try linking many, more than 10, object files that all use template 
> heavily. Of course it could be that your system has a binutils that 
> doesn't have the "bug" ;-)

I'm using it to create boost.python and some extension modules. But I have 
to admit I didn't really time it, it has just been my personal impression.

>>Is there some way to disable the use of objcopy, besides 
>>creating a new tools file?

> Hm, it doesn't look like it :-( It hadn't come up until now, it's easy 
> enough to check for some option (--no-objcopy) on the invocation. Of 
> course I wonder why is it that the link doesn't work for you given that 
> all BBv1 does with objcopy is remove the 'readonly' flag from debug_str 
> sections.

Nono, it's _pre_link not working. It seems that objcopy disturbs some order 
prelink expects to find in the object file.

> So one question I have; What is the version of binutils you are using?

-> objcopy --version
GNU objcopy 2.14.90.0.4 20030523
Copyright 2002 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License. This program has absolutely no warranty.

-> rpm -q prelink
prelink-0.3.2-2.EL
-> prelink --version
prelink 1.0

BTW, I need prelink to relocate my python extension module, to allow it to 
cooperate with an external library that has a fixed location for a shared 
memory segment, which unfortunately collides with the standard location 
where the module is mapped when loaded by the python interpreter.

Markus