Box is using distcc, because of this CFLAGS has -march=native inlined (a.k.a. the expanded flags are set in /etc/porage/make.conf). My CPU has the -msahf option enabled which breaks configure for this package. Issue is present with both 2.0.3 and 2.0.4 versions.
Created attachment 452490 [details] Build log
Created attachment 452492 [details] config log
Same build log here with both inline & -march=native in then following environment: emerge --info Portage 2.3.0 (python 2.7.12-final-0, default/linux/amd64/13.0, gcc-5.4.0, glibc-2.22-r4, 4.8.15-gentoo-krnlschd x86_64) ================================================================= System uname: Linux-4.8.15-gentoo-krnlschd-x86_64-Intel-R-_Core-TM-_i3-3217U_CPU_@_1.80GHz-with-gentoo-2.3 KiB Mem: 8051408 total, 6795728 free KiB Swap: 8048528 total, 8048528 free Timestamp of repository gentoo: Fri, 30 Dec 2016 09:45:02 +0000 sh bash 4.3_p48-r1 ld GNU ld (Gentoo 2.27 p1.0) 2.27 distcc[5457] (dcc_trace_version) distcc 3.2rc1 x86_64-pc-linux-gnu; built Dec 23 2016 17:08:13 [disabled] ccache version 3.2.4 [disabled] app-shells/bash: 4.3_p48-r1::gentoo dev-java/java-config: 2.2.0-r3::gentoo dev-lang/perl: 5.22.3_rc4::gentoo dev-lang/python: 2.7.12::gentoo, 3.4.5::gentoo, 3.5.2::gentoo dev-util/ccache: 3.2.4::gentoo dev-util/cmake: 3.6.3::gentoo dev-util/pkgconfig: 0.28-r2::gentoo sys-apps/baselayout: 2.3::gentoo sys-apps/openrc: 0.22.4::gentoo sys-apps/sandbox: 2.10-r1::gentoo sys-devel/autoconf: 2.13::gentoo, 2.69::gentoo sys-devel/automake: 1.11.6-r1::gentoo, 1.12.6::gentoo, 1.14.1::gentoo, 1.15::gentoo sys-devel/binutils: 2.25.1-r1::gentoo, 2.26.1::gentoo, 2.27::gentoo sys-devel/gcc: 5.4.0::gentoo sys-devel/gcc-config: 1.7.3::gentoo sys-devel/libtool: 2.4.6-r2::gentoo sys-devel/make: 4.1-r1::gentoo sys-kernel/linux-headers: 4.9::gentoo (virtual/os-headers) sys-libs/glibc: 2.22-r4::gentoo Repositories: c2p-overlay location: /var/lib/layman/c2p-overlay masters: gentoo priority: -10001 jorgicio location: /var/lib/layman/jorgicio masters: gentoo priority: -10001 rindeal location: /var/lib/layman/rindeal masters: gentoo priority: -10001 sublime-text location: /var/lib/layman/sublime-text masters: gentoo priority: -10001 gentoo location: /usr/portage sync-type: rsync sync-uri: rsync://rsync.europe.gentoo.org/gentoo-portage priority: -1000 sync-rsync-extra-opts: --timeout=600 x-portage location: /usr/local/portage masters: gentoo priority: 0 bar location: /var/lib/layman/bar masters: gentoo priority: 50 Installed sets: @gcc-toolchain ACCEPT_KEYWORDS="amd64" ACCEPT_LICENSE="* -@EULA" CBUILD="x86_64-pc-linux-gnu" CFLAGS="-march=ivybridge -mmmx -mno-3dnow -msse -msse2 -msse3 -mssse3 -mno-sse4a -mcx16 -msahf -mno-movbe -mno-aes -mno-sha -mpclmul -mpopcnt -mno-abm -mno-lwp -mno-fma -mno-fma4 -mno-xop -mno-bmi -mno-bmi2 -mno-tbm -mavx -mno-avx2 -msse4.2 -msse4.1 -mno-lzcnt -mno-rtm -mno-hle -mno-rdrnd -mf16c -mfsgsbase -mno-rdseed -mno-prfchw -mno-adx -mfxsr -mxsave -mxsaveopt -mno-avx512f -mno-avx512er -mno-avx512cd -mno-avx512pf -mno-prefetchwt1 --param l1-cache-size=32 --param l1-cache-line-size=64 --param l2-cache-size=3072 -mtune=ivybridge -O2 -pipe -fgraphite -flto=4 -flto-compression-level=9 -fopenmp -floop-block -floop-interchange -floop-strip-mine -ftree-loop-distribution -ftree-loop-linear -ftree-vectorize" CHOST="x86_64-pc-linux-gnu" CONFIG_PROTECT="/etc /usr/share/config /usr/share/gnupg/qualified.txt /usr/share/maven-bin-3.3/conf /var/lib/hsqldb" CONFIG_PROTECT_MASK="/etc/ca-certificates.conf /etc/dconf /etc/env.d /etc/fonts/fonts.conf /etc/gconf /etc/gentoo-release /etc/php/apache2-php5.6/ext-active/ /etc/php/cgi-php5.6/ext-active/ /etc/php/cli-php5.6/ext-active/ /etc/revdep-rebuild /etc/sandbox.d /etc/splash /etc/terminfo" CXXFLAGS="-march=ivybridge -mmmx -mno-3dnow -msse -msse2 -msse3 -mssse3 -mno-sse4a -mcx16 -msahf -mno-movbe -mno-aes -mno-sha -mpclmul -mpopcnt -mno-abm -mno-lwp -mno-fma -mno-fma4 -mno-xop -mno-bmi -mno-bmi2 -mno-tbm -mavx -mno-avx2 -msse4.2 -msse4.1 -mno-lzcnt -mno-rtm -mno-hle -mno-rdrnd -mf16c -mfsgsbase -mno-rdseed -mno-prfchw -mno-adx -mfxsr -mxsave -mxsaveopt -mno-avx512f -mno-avx512er -mno-avx512cd -mno-avx512pf -mno-prefetchwt1 --param l1-cache-size=32 --param l1-cache-line-size=64 --param l2-cache-size=3072 -mtune=ivybridge -O2 -pipe -fgraphite -flto=4 -flto-compression-level=9 -fopenmp -floop-block -floop-interchange -floop-strip-mine -ftree-loop-distribution -ftree-loop-linear -ftree-vectorize" DISTDIR="/usr/distfiles" EMERGE_DEFAULT_OPTS="--autounmask=n --misspell-suggestions=n --nospinner --tree --with-bdeps=y" FCFLAGS="-O2 -pipe" FEATURES="assume-digests binpkg-logs config-protect-if-modified distlocks ebuild-locks fixlafiles merge-sync news parallel-fetch preserve-libs protect-owned sandbox sfperms strict unknown-features-warn unmerge-logs unmerge-orphans userfetch userpriv usersandbox usersync" FFLAGS="-O2 -pipe" GENTOO_MIRRORS="http://gentoo.mirrors.ovh.net/gentoo-distfiles/ http://mirrors.linuxant.fr/distfiles.gentoo.org/ http://mirrors.stuhome.net/gentoo/ rsync://ftp.df.lth.se/pub/gentoo/ http://gentoo.mirrors.easynews.com/linux/gentoo/ ftp://mirror.neolabs.kz/gentoo/pub http://mirror.usu.edu/mirrors/gentoo/ http://mirror.iawnet.sandia.gov/gentoo/ rsync://gentoo.c3sl.ufpr.br/gentoo/ ftp://gentoo.c3sl.ufpr.br/gentoo/ http://ftp.swin.edu.au/gentoo ftp://ftp.swin.edu.au/gentoo" LANG="fr_FR.utf8" LDFLAGS="-Wl,-O2 -Wl,--enable-new-dtags -Wl,--as-needed -Wl,--sort-common -s -flto=4" MAKEOPTS="-j4 -l4" PKGDIR="/usr/portage/packages" PORTAGE_COMPRESS="lzma" PORTAGE_COMPRESS_FLAGS="-9" PORTAGE_CONFIGROOT="/" PORTAGE_RSYNC_EXTRA_OPTS="--timeout=600" PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --omit-dir-times --compress --force --whole-file --delete --stats --human-readable --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages --exclude=/.git" PORTAGE_TMPDIR="/var/tmp" USE="X acl amd64 bluetooth bzip2 cli consolekit cracklib crypt cxx dbus dri egl fftw fortran gdbm gif gles gles1 gles2 iconv icu jack jpeg2k mmx mmxext modules multilib multislot ncurses nls nptl openal opengl openmp pam pch pcre png policykit pulseaudio qt5 readline seccomp session sndfile sse sse2 sse4_1 ssl ssse3 svg system-icu tcpd threads tiff truetype udev udisks unicode upower v4l vaapi vdpau xinerama xvmc zlib" ABI_X86="64" ALSA_CARDS="ali5451 als4000 atiixp atiixp-modem bt87x ca0106 cmipci emu10k1x ens1370 ens1371 es1938 es1968 fm801 hda-intel intel8x0 intel8x0m maestro3 trident usb-audio via82xx via82xx-modem ymfpci" APACHE2_MODULES="authn_core authz_core socache_shmcb unixd actions alias auth_basic authn_alias authn_anon authn_dbm authn_default authn_file authz_dbm authz_default authz_groupfile authz_host authz_owner authz_user autoindex cache cgi cgid dav dav_fs dav_lock deflate dir disk_cache env expires ext_filter file_cache filter headers include info log_config logio mem_cache mime mime_magic negotiation rewrite setenvif speling status unique_id userdir usertrack vhost_alias" CALLIGRA_FEATURES="kexi words flow plan sheets stage tables krita karbon braindump author" CAMERAS="ptp2" COLLECTD_PLUGINS="df interface irq load memory rrdtool swap syslog" CPU_FLAGS_X86="avx mmx mmxext popcnt sse sse2 sse3 sse4_1 sse4_2 ssse3" ELIBC="glibc" GPSD_PROTOCOLS="ashtech aivdm earthmate evermore fv18 garmin garmintxt gpsclock itrax mtk3301 nmea ntrip navcom oceanserver oldstyle oncore rtcm104v2 rtcm104v3 sirf superstar2 timing tsip tripmate tnt ublox ubx" INPUT_DEVICES="evdev synaptics" KERNEL="linux" L10N="fr" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" LIBREOFFICE_EXTENSIONS="presenter-console presenter-minimizer" LINGUAS="fr" OFFICE_IMPLEMENTATION="libreoffice" PHP_TARGETS="php5-6" PYTHON_SINGLE_TARGET="python2_7" PYTHON_TARGETS="python2_7 python3_4 python3_5" RUBY_TARGETS="ruby21" SANE_BACKENDS="artec_eplus48u" USERLAND="GNU" VIDEO_CARDS="intel i965" XTABLES_ADDONS="quota2 psd pknock lscan length2 ipv4options ipset ipp2p iface geoip fuzzy condition tee tarpit sysrq steal rawnat logmark ipmark dhcpmac delude chaos account" USE_PYTHON="2.7 3.4 3.5" Unset: CC, CPPFLAGS, CTARGET, CXX, INSTALL_MASK, LC_ALL, PORTAGE_BUNZIP2_COMMAND
The problem isn't your CFLAGS, it's that CC isn't respected. This package is using clang by default (which isn't even listed as a dep). It also chokes on CFLAGS="-frecord-gcc-switches" and even LDFLAGS="-Wl,--hash-style=gnu", things recommended for gentoo developers....
commit 2dd28e7d847aca22cd0901f482a0c3c97b73ef5e Author: Alexis Ballier <aballier@gentoo.org> Date: Thu Feb 9 14:27:19 2017 +0100 media-video/guvcview: Bump to 2.0.5. Export CC/CXX to avoid its autoconf script picking up clang, bug #599030.
