[gentoo-embedded] crossdev, alternate root, and build dependencies

[Dustin C. Hatch]

(Originally posted on gentoo-user, but may be more appropriate here)

I am trying to understand and use crossdev to build Gentoo for my 
Raspberry Pi, and I have a couple of questions. I was able to 
successfully build a toolchain::

     crossdev -S -t armv6j-hardfloat-linux-gnueabi

This correctly installed binutils, gcc, glibc, and linux-headers::

     equery list cross-armv6j-hardfloat-linux-gnueabi/*
      * Searching for * in cross-armv6j-hardfloat-linux-gnueabi ...
     [I-O] [  ] cross-armv6j-hardfloat-linux-gnueabi/binutils-2.22-r1:0
     [I-O] [  ] cross-armv6j-hardfloat-linux-gnueabi/gcc-4.5.4:4.5
     [I-O] [  ] cross-armv6j-hardfloat-linux-gnueabi/glibc-2.15-r3:2.2
     [I-O] [  ] cross-armv6j-hardfloat-linux-gnueabi/linux-headers-3.6:0

I then copied the configuration from 
/usr/armv6j-hardfloat-linux-gnueabi/etc/portage to an alternate 
location, so I could modify it without impacting the crossdev toolchain. 
Next, I started to emerge some ebuilds into a staging directory using 
the following commands::

     export CBUILD=$(portageq envvar CHOST)
     export PORTAGE_CONFIGROOT=/home/dustin/rpi-build/configroot
     export ROOT=/home/dustin/rpi-build/buildroot/
     export PORTAGE_TMPDIR=/home/dusitn/rpi-build/tmp
     emerge --nodeps baselayout
     emerge --onlydeps baselayout

The first pass completed successfully, but the second failed to build 
psmisc::

     checking for tgetent in -ltinfo... no
     checking for tgetent in -lncurses... no
     checking for tgetent in -ltermcap... no
     configure: error: Cannot find tinfo, ncurses or termcap libraries

config.log shows this::

     configure:3970: checking for tgetent in -lncurses
     configure:3995: armv6j-hardfloat-linux-gnueabi-gcc -o conftest -O4
     -pipe -mfpu=vfp -mfloat-abi=hard -march=armv6zk -mtune=arm1176jzf-s
     -fomit-frame-pointer   conftest.c -lncurses   >&5
     /usr/libexec/gcc/armv6j-hardfloat-linux-gnueabi/ld: cannot find
     -lncurses
     collect2: ld returned 1 exit status
     configure:3995: $? = 1

ncurses did get installed in the alternate root::

     ls -1 ${ROOT}lib/libncurses*
     /home/dustin/rpi-build/buildroot/lib/libncurses.so.5
     /home/dustin/rpi-build/buildroot/lib/libncurses.so.5.9
     /home/dustin/rpi-build/buildroot/lib/libncursesw.so.5
     /home/dustin/rpi-build/buildroot/lib/libncursesw.so.5.9

Now, I've found that if I install ncurses in /usr/${CHOST} instead of 
${ROOT}, psmisc will build successfully. I am thus confused on where 
things are supposed to be built. The Cross Development Guide says not to 
install pieces of the toolchain in /usr/${CHOST}, but some ebuilds, like 
openrc, have explicit RDEPENDs on them, so emerge pulls them in. I'm not 
sure how to resolve this seeming catch-22 where I can't install runtime 
dependencies in /usr/${CHOST}, but I also can't install build 
dependencies in in ${ROOT}.

I am hoping to have this process scriptable, so my current method of 
just installing missing build dependencies in /usr/${CHOST} after 
something fails won't work. Any pointers would be appreciated.

Thanks,

-- 
♫Dustin