# clang is built with +default-lld.


$ cd /etc/portage/
$ cat package.env

# clang + thinlto is default.

## Move package downwards in the list until it compiles.
## Bug# is for bugs.gentoo.org

# clang, no lto
media-libs/alsa-lib clang-no-lto.conf #616108 #669086
media-libs/dav1d clang-no-lto.conf #801172
sys-apps/pciutils clang-no-lto.conf #852929
sys-fs/fuse clang-no-lto.conf #853058
sys-libs/libxcrypt clang-no-lto.conf #852917 (doesn't work with lto says upstream)

# gcc, with lto
media-video/pipewire gcc-with-lto.conf #802162
sys-devel/gcc gcc-with-lto.conf
sys-libs/glibc gcc-with-lto.conf

# gcc, no lto
media-libs/x264 gcc-no-lto.conf #497714
media-video/ffmpeg gcc-no-lto.conf #772854
sys-kernel/gentoo-kernel gcc-no-lto.conf # needs some workarounds for clang+thinlto, easier with gentoo-sources

# textrels (https://wiki.gentoo.org/wiki/Hardened/Textrels_Guide)
media-libs/libass clang-lto-textrels.conf
media-libs/openh264 clang-lto-textrels.conf
media-libs/x265 clang-lto-textrels.conf
media-libs/xvid clang-lto-textrels.conf

# misc, package-specific solutions, other env overrides
# mail-client/thunderbird firefox2.conf
# www-client/firefox firefox2.conf




$ cat make.conf

ACCEPT_KEYWORDS="amd64"

CC="clang"
CXX="clang++"
CFLAGS="-march=native -O3 -pipe -flto=thin"
CXXFLAGS="${CFLAGS}"
LDFLAGS="-Wl,-O2 -Wl,--as-needed"

AR="llvm-ar"
NM="llvm-nm"
RANLIB="llvm-ranlib"

MAKEOPTS="-j32"

ACCEPT_LICENSE="*"
EMERGE_DEFAULT_OPTS="--jobs=10"
FEATURES="parallel-fetch parallel-install"
GENTOO_MIRRORS="https://ftp-stud.hs-esslingen.de/pub/Mirrors/gentoo/"
PORTAGE_NICENESS=19
PORTAGE_TMPDIR="/var/tmp"

CPU_FLAGS_X86="aes avx avx2 f16c fma3 mmx mmxext pclmul popcnt sha sse sse2 
sse3 sse4_1 sse4_2 sse4a ssse3"

INPUT_DEVICES="joystick libinput"
SANE_BACKENDS="pixma"
VIDEO_CARDS="amdgpu radeonsi"

L10N="
en 
en_US 
en-US 
fi 
sv
"
LINGUAS="${L10N}"

ABI_X86="64 32"
SYMLINK_LIB=no
LIBDIR_x86=lib

USE="
archive -avahi 
-bluetooth 
-cdda clang -consolekit 
dbus drm -dvd 
elogind -emoji 
ffmpeg fontconfig freetype 
-geolocation -gnome -gnome-online-accounts -gold gstreamer -gtk-doc gtk3 
harfbuzz 
-ibus -ipv6 
jpeg2k 
-ldap libglvnd -libsecret lto 
-networkmanager -nls 
openrc 
pulseaudio 
-qt5 
rar 
-spell -static-libs -systemd 
theora threads 
udev 
vaapi vdpau vim-syntax voikko vulkan 
-weather -wifi -wlan 
xinerama 
-zeroconf
"




$ cat env/clang-no-lto.conf

CC="clang"
CXX="clang++"

CFLAGS="-march=native -O3 -pipe"
CXXFLAGS="${CFLAGS}"
LDFLAGS="-Wl,-O2 -Wl,--as-needed"




$ cat env/clang-lto-textrels.conf

CC="clang"
CXX="clang++"

CFLAGS="-march=native -O3 -pipe -flto=thin"
CXXFLAGS="${CFLAGS}"
LDFLAGS="-Wl,-z,notext"




$ cat env/gcc-no-lto.conf

CC="gcc"
CXX="g++"

CFLAGS="-march=native -O3 -pipe"
CXXFLAGS="${CFLAGS}"
LDFLAGS="-Wl,-O2 -Wl,--as-needed"

AR="gcc-ar"
NM="gcc-nm"
RANLIB="gcc-ranlib"




$ cat env/gcc-with-lto.conf

CC="gcc"
CXX="g++"

CFLAGS="-flto=32 -march=native -O3 -pipe"
CXXFLAGS="${CFLAGS}"
LDFLAGS="-Wl,-O2 -Wl,--as-needed"

AR="gcc-ar"
NM="gcc-nm"
RANLIB="gcc-ranlib"




$ cat env/firefox.conf

CFLAGS="-march=native -O3 -pipe -fno-sized-deallocation -fno-aligned-new -fno-strict-aliasing -fPIC -fno-math-errno -fno-exceptions"
CXXFLAGS="${CFLAGS}"