Bugzilla Bug 142395

../../Archive/7z/../../Compress/Deflate/DeflateDecoder.h:50: error: extra
qualification 'NCompress::
NDeflate::NDecoder::CCoder::' on member 'ReleaseStreams'
...

../../Archive/7z/../../Compress/Deflate/DeflateEncoder.h:119: error: extra
qualification 'NCompress:
:NDeflate::NEncoder::CCoder::' on member 'ReleaseStreams'

make[1]: *** [7zEncode.o] Error 1
make[1]: Leaving directory
`/var/tmp/portage/p7zip-4.20/work/p7zip_4.20/7zip/Bundles/Alone'
make: *** [7za] Error 2

!!! ERROR: app-arch/p7zip-4.20 failed.
Call stack:
  ebuild.sh, line 1539:   Called dyn_compile
  ebuild.sh, line 939:   Called src_compile
  p7zip-4.20.ebuild, line 30:   Called die


emerge --info

Portage 2.1-r1 (default-linux/amd64/2006.0, gcc-4.1.1, glibc-2.4-r3,
2.6.17-gentoo-r2 x86_64)
=================================================================
System uname: 2.6.17-gentoo-r2 x86_64 Intel(R) Pentium(R) D  CPU 2.66GHz
Gentoo Base System version 1.6.15
distcc 2.18.3 x86_64-pc-linux-gnu (protocols 1 and 2) (default port 3632)
[disabled]
app-admin/eselect-compiler: [Not Present]
dev-lang/python:     2.4.2
dev-python/pycrypto: 2.0.1-r5
dev-util/ccache:     [Not Present]
dev-util/confcache:  [Not Present]
sys-apps/sandbox:    1.2.12
sys-devel/autoconf:  2.13, 2.59-r6
sys-devel/automake:  1.4_p6, 1.5, 1.6.3, 1.7.9-r1, 1.8.5-r3, 1.9.6-r1
sys-devel/binutils:  2.16.1-r3
sys-devel/gcc-config: 1.3.12-r6
sys-devel/libtool:   1.5.22
virtual/os-headers:  2.6.11-r2
ACCEPT_KEYWORDS="amd64"
AUTOCLEAN="yes"
CBUILD="x86_64-pc-linux-gnu"
CFLAGS="-march=nocona -O2 -fomit-frame-pointer -pipe"
CHOST="x86_64-pc-linux-gnu"
CONFIG_PROTECT="/etc /usr/share/X11/xkb"
CONFIG_PROTECT_MASK="/etc/env.d /etc/gconf /etc/terminfo"
CXXFLAGS="-march=nocona -O2 -fomit-frame-pointer -pipe"
DISTDIR="/usr/portage/distfiles"
FEATURES="autoconfig distlocks metadata-transfer sandbox sfperms strict"
GENTOO_MIRRORS="ftp://ftp.linux.ee/pub/gentoo/distfiles/
ftp://ftp.du.se/pub/os/gentoo http://trumpetti.atm.tut.fi/gentoo/"
LINGUAS="en en_GB ru"
MAKEOPTS="-j3"
PKGDIR="/usr/portage/packages"
PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --compress
--force --whole-file --delete --delete-after --stats --timeout=180
--exclude='/distfiles' --exclude='/local' --exclude='/packages'"
PORTAGE_TMPDIR="/var/tmp"
PORTDIR="/usr/portage"
SYNC="rsync://rsync.gentoo.org/gentoo-portage"
USE="amd64 X acpi alsa avi bash-completion bitmap-fonts bittorrent cjk cli
crypt cups dlloader dri eds emboss encode exif fbcon ffmpeg firefox flac fltk
foomaticdb gif gimp gpm gs gstreamer gtk gtk2 h323 hddtemp imagemagick imlib
innodb isdnlog java jpeg jpeg2k lm_sensors lzw lzw-tiff mad matroska mime mjpeg
mozsvg mp3 mpeg mplayer ncurses nls nptl nptlonly nsplugin nvidia ogg opengl
pam pcre pdflib perl png pppd python qt qt3 qt4 quicktime readline reflection
samba scanner sdl session slp sndfile snmp spell spl ssl svg tcpd tiff truetype
truetype-fonts type1-fonts unicode usb video_cards_nv vorbis xmms xorg xpm xv
xvid xvmc zlib elibc_glibc input_devices_keyboard input_devices_mouse
input_devices_evdev kernel_linux linguas_en linguas_en_GB linguas_ru
userland_GNU video_cards_vesa"
Unset:  CTARGET, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LANG, LC_ALL, LDFLAGS,
PORTAGE_RSYNC_EXTRA_OPTS, PORTDIR_OVERLAY

You need a newer version for gcc-4.1, been fixed quite some time ago.

stable on amd64.