binutils_notes...

[Jerry McBride]

On Wed, 04 Sep 2002 20:58:07 -0400 Douglas J Hunley <doug at hunley.homeip.net>
wrote:

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> Jerry McBride spewed electrons into the ether that resembled:
> > Same gcc here and I've been using it.It's a ld enabled switch that appears
> > in binutils 2.12.1 or there
> > abouts. Works.
> 
> how do you turn it on?
> 

Here's a text file I snipped off the inet. Not real long, but should prove to
be good read. Also, pay a visit to http://objprelink.sourceforge.net for an
updated version of objprelink....

--- combreloc.text follows ---


TITLE:		Setting up combreloc on recent binutils
LFS VERSION:	3.3+ (maybe earlier)
AUTHOR:		Zack Winkles <sativa93 at bellsouth.net>

SYNOPSIS:
	Configuring/tricking binutils to use the -z combreloc option

HINT:
Contents

	* Introduction
	* Methods
	* Problems

Introduction

   Recent versions of binutils (actually its ld) include a new option that
   reaps the same loading inprovements as objprelink of KDE fame, but for
   all programs compiled by it. As a general rule you can expect around 20%
   to 30% faster loading times. I personally have had no problems compiling
   *EVERYTHING* on my system with it (including gcc, glibc, etc).

Methods

   Here's the real meat of it all. Even though all you really need to do is
   to link the program with this option, it can be quite hard getting all of
   your options passed down to ld. One particular example is gcc. To get it
   to use the option on its libgcc_s.so binary you have to set about eight
   environmental variables and edit a few Makefiles. But if you want to do it
   that way the proper was is to set the LDFLAGS variable:

	export LDFLAGS='-z combreloc'

   should work. I'd estimate about 50% of packages actually recognize and use
   that variable though. We don't want to stop there do we? Let's take it a
   step further and set the CFLAGS variable too:

	export CFLAGS='**YOUR_CFLAGS** -z combreloc'
	export CXXFLAGS='**YOUR_CFLAGS** -z combreloc'

   If you don't understand why I set CXXFLAGS too you have worse things to
   worry about than loading times on a computer... Onward. Even then programs
   like bzip2 won't be optimized. Let's take it further:

	export CC='gcc -z combreloc'
	export CXX='g++ -z combreloc'

   Think that's good enough of a job? I sure don't. When compiling gcc it
   doesn't care about any of your flags: it ignores them all and uses its
   own tags and compilers. Here's the easiest/most aggressive method to do
   this for your entire system. WARNING: All programs you compile with have
   -z combreloc run on ld. There is no longer a way to use ld without the
   option outside of calling ld.orig or removing the script and moving
   ld.orig to ld (the reverse of the following instructions).

	mv /usr/bin/ld /usr/bin/ld.orig &&
	cat > /usr/bin/ld << "EOF"
	#!/bin/sh
	# Begin /usr/bin/ld
	# Wrapper script to use -z combreloc option on all executables
	# By: Zack Winkles

	exec /usr/bin/ld.orig -z combreloc "$@"

	# End /usr/bin/ld
	EOF
	chmod 755 /usr/bin/ld

   Now you can unset CC, CFLAGS, and all the other stuff we did before in
   the hint. Aren't you glad you read the whole hint ;). There's just one
   last issue to address. When initially compiling the system and you're in
   the static chroot'd environment, how do you get your stuff optimized then?
   its pretty easy actually. Take the above instructions and modify every
   instance of /usr/bin to /static/bin. Then even the static binutils will
   optimize. Pretty easy ay?

Problems

   So far I have never had a single problem with anything I compiled using
   even the most aggressive method listed. The only thing I've noticed is
   better performance. If you have any problems let me know and I'll try to
   help you out.






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