What is easiest way to build a BSD 8 binary on a BSD 7 box?

[Peter Steele]

Okay, that looks doable. I'll see how this works out. Thanks very much for the info!

-----Original Message-----
From: Pieter de Goeje [mailto:pieter at degoeje.nl] 
Sent: Saturday, February 06, 2010 5:28 PM
To: freebsd-questions at freebsd.org
Cc: Peter Steele
Subject: Re: What is easiest way to build a BSD 8 binary on a BSD 7 box?

On Saturday 06 February 2010 20:22:13 Peter Steele wrote:
> I have a BSD 7 system with the full BSD 8 sources loaded on it, and we 
> use this box to build our custom BSD 8 kernel and tools. We do not 
> install the custom code on the BSD 7 box but simply collect the 
> artifacts as a basis for our custom BSD 8 image. I have a standalone 
> tool that has previously been built on this same BSD 7 system, but it 
> just uses gcc and links against the normal BSD 7 libraries that are located on this box.
>
> When we run this tool on a BSD 7 box it works fine. However, we've 
> discovered one function it performs doesn't work properly. It uses 
> kvm_read to collect network statistics and apparently applications 
> that use this function have to be linked against the libraries of the actual target OS.
> One easy solution of course is to build our tool on a BSD 8 box, and 
> in the long run we'll likely go that route as we move away from BSD 7. 
> Right now though our build server is BSD 7 and we need to build this 
> tool against BSD
> 8 libraries. This obviously can be done since "make world" does 
> exactly that-it builds everything against 8.0 objects even if the 
> build is done on a BSD 7 box.
>
> Without dissecting the magic going on in "make world", can any explain 
> how I could do the same thing with my standalone tool? Specifically, 
> build it on a BSD 7 box but link it against BSD 8 libraries.

The easiest way would probably be the following.

# SOMEDIR=/path/to/fbsd8buildenv
# mkdir -p ${SOMEDIR}
# cd /path/to/FreeBSD-8.0/src
# make buildworld
# make installworld DESTDIR=${SOMEDIR}

Then adding --sysroot=${SOMEDIR} to all invocations of gcc/ld and/or liberal use of -I and -L gcc options should do the trick.

For example:
# export CFLAGS="-I${SOMEDIR}/usr/include -L${SOMEDIR}/lib -L${SOMEDIR}/usr/lib # make

Regards,

Pieter de Goeje