Currently, without hacking toolchain.eclass, it is not possible to build a crossdev GCC and give it custom *FLAGS. Regardless of the custom-cflags useflag, or whatever the environment *FLAGS are, the block at toolchain.eclass:1482 forcibly resets CFLAGS and other *FLAGS to "-O2 -pipe". Reproducible: Always Steps to Reproduce: 1. Add -g to CFLAGS and CXXFLAGS somehow (env/ and package.env/ is an option) when building a gcc cross compiler with crossdev, and enable FEATURES splitdebug and installsources 2. Try to debug said cross compiler using GDB Actual Results: No debugging symbols found Expected Results: Debugging symbols found Specifically, this is the check in the toolchain.eclass: # these are set here so we have something sane at configure time if is_crosscompile ; then # Set this to something sane for both native and target CFLAGS="-O2 -pipe" FFLAGS=${CFLAGS} FCFLAGS=${CFLAGS} # "hppa2.0-unknown-linux-gnu" -> hppa2_0_unknown_linux_gnu local VAR="CFLAGS_"${CTARGET//[-.]/_} CXXFLAGS=${!VAR-${CFLAGS}} fi If I edit the line where CFLAGS is set to include -g, debugging symbols are properly added and I can debug GCC properly (In fact, this is how I was able to find the problem for bug #792291). Here's my emerge --info: Portage 3.0.18 (python 3.8.10-final-0, default/linux/amd64/17.1/desktop/plasma, gcc-11.1.0, glibc-2.33, 5.12.2-gentoo x86_64) ================================================================= System uname: Linux-5.12.2-gentoo-x86_64-Intel-R-_Core-TM-_i7-3770K_CPU_@_3.50GHz-with-glibc2.2.5 KiB Mem: 16350004 total, 373476 free KiB Swap: 16776192 total, 11893496 free Timestamp of repository gentoo: Wed, 26 May 2021 20:20:09 +0000 Head commit of repository gentoo: 3b346c4b56d42f859216f8740f719cbd4bcf4926 sh bash 5.1_p8 ld GNU ld (Gentoo 2.36.1 p3) 2.36.1 distcc 3.4 x86_64-pc-linux-gnu [disabled] ccache version 4.3 [disabled] app-shells/bash: 5.1_p8::gentoo dev-java/java-config: 2.3.1::gentoo dev-lang/perl: 5.32.1::gentoo dev-lang/python: 2.7.18_p10::gentoo, 3.7.10_p3::gentoo, 3.8.10_p1::gentoo, 3.9.5_p1::gentoo, 3.10.0_beta1::gentoo dev-lang/rust: 1.52.1::gentoo dev-util/ccache: 4.3::gentoo dev-util/cmake: 3.20.2::gentoo dev-util/pkgconfig: 0.29.2::gentoo sys-apps/baselayout: 2.7-r2::gentoo sys-apps/openrc: 0.43.3::gentoo sys-apps/sandbox: 2.24::gentoo sys-devel/autoconf: 2.13-r1::gentoo, 2.69-r5::gentoo sys-devel/automake: 1.16.3-r1::gentoo sys-devel/binutils: 2.36.1-r1::gentoo sys-devel/gcc: 10.3.0::gentoo, 11.1.0::gentoo sys-devel/gcc-config: 2.4::gentoo sys-devel/libtool: 2.4.6-r6::gentoo sys-devel/make: 4.3::gentoo sys-kernel/linux-headers: 5.12::gentoo (virtual/os-headers) sys-libs/glibc: 2.33::gentoo Repositories: gentoo location: /var/db/repos/gentoo sync-type: git sync-uri: git://github.com/gentoo-mirror/gentoo priority: -1000 sync-git-verify-commit-signature: true Local_Overlay location: /var/db/repos/local masters: gentoo eclass-overrides: gentoo Local_Overlay crossdev location: /var/db/repos/crossdev masters: gentoo eclass-overrides: gentoo crossdev brother-overlay location: /var/lib/layman/brother-overlay masters: gentoo priority: 50 guru location: /var/lib/layman/guru sync-type: laymansync sync-uri: https://anongit.gentoo.org/git/repo/proj/guru.git masters: gentoo priority: 50 ACCEPT_KEYWORDS="amd64 ~amd64" ACCEPT_LICENSE="@FREE" CBUILD="x86_64-pc-linux-gnu" CFLAGS="-march=ivybridge -pipe -fomit-frame-pointer -O3 -flto" CHOST="x86_64-pc-linux-gnu" CONFIG_PROTECT="/etc /opt/brother/scanner/brscan4/brsanenetdevice4.cfg /usr/lib64/libreoffice/program/sofficerc /usr/share/config /usr/share/gnupg/qualified.txt" CONFIG_PROTECT_MASK="/etc/ca-certificates.conf /etc/dconf /etc/env.d /etc/fonts/fonts.conf /etc/gconf /etc/gentoo-release /etc/revdep-rebuild /etc/sandbox.d /etc/terminfo /etc/texmf/language.dat.d /etc/texmf/language.def.d /etc/texmf/updmap.d /etc/texmf/web2c" CXXFLAGS="-march=ivybridge -pipe -fomit-frame-pointer -O3 -flto" DISTDIR="/var/cache/distfiles" ENV_UNSET="CARGO_HOME DBUS_SESSION_BUS_ADDRESS DISPLAY GOBIN GOPATH PERL5LIB PERL5OPT PERLPREFIX PERL_CORE PERL_MB_OPT PERL_MM_OPT XAUTHORITY XDG_CACHE_HOME XDG_CONFIG_HOME XDG_DATA_HOME XDG_RUNTIME_DIR" FCFLAGS="-march=ivybridge -pipe -fomit-frame-pointer -O3 -flto" FEATURES="assume-digests binpkg-docompress binpkg-dostrip binpkg-logs binpkg-multi-instance clean-logs config-protect-if-modified distlocks ebuild-locks fixlafiles ipc-sandbox merge-sync multilib-strict network-sandbox news parallel-fetch pid-sandbox preserve-libs protect-owned qa-unresolved-soname-deps sandbox sfperms split-log strict unknown-features-warn unmerge-logs unmerge-orphans userfetch userpriv usersandbox usersync xattr" FFLAGS="-march=ivybridge -pipe -fomit-frame-pointer -O3 -flto" GENTOO_MIRRORS="http://distfiles.gentoo.org" LANG="en_US.utf8" LDFLAGS="-Wl,-O1 -Wl,--as-needed" LINGUAS="en es" MAKEOPTS="-j9" PKGDIR="/var/cache/binpkgs" PORTAGE_CONFIGROOT="/" 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="/tmp" USE="=-ppp X a52 aac acl acpi activities alsa amd64 avx bash-completion berkdb bluetooth branding bzip2 cairo cdda cdr cli crypt cups dbus declarative dri dts dvd dvdr elogind emboss encode exif flac fortran gdbm gif gpm gtk gui iconv icu ipv6 jpeg kde kipi kwallet lcms libglvnd libnotify libtirpc lm-sensors lto mad mmx mng mp3 mp4 mpeg mtp multilib ncurses nls nptl nvidia ogg opengl openmp pam pango pcre pdf phonon plasma png policykit ppds pulseaudio qml qt qt5 readline sdl seccomp semantic-desktop spell split-usr sse sse2 sse3 sse4 ssl startup-notification svg tcpd tiff truetype udev udisks unicode upower usb vdpau vorbis widgets wxwidgets x264 xattr xcb xml xv xvid zeroconf zlib" ABI_X86="64" ADA_TARGET="gnat_2018" 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="karbon sheets words" COLLECTD_PLUGINS="df interface irq load memory rrdtool swap syslog" CPU_FLAGS_X86="mmx mmxext sse sse2 aes avx f16c pclmul popcnt rdrand sse3 sse4_1 sse4_2 ssse3" ELIBC="glibc" GPSD_PROTOCOLS="ashtech aivdm earthmate evermore fv18 garmin garmintxt gpsclock greis isync itrax mtk3301 nmea ntrip navcom oceanserver oldstyle oncore rtcm104v2 rtcm104v3 sirf skytraq superstar2 timing tsip tripmate tnt ublox ubx" GRUB_PLATFORMS="efi-64 emu" INPUT_DEVICES="evdev roccat_tyon" KERNEL="linux" L10N="en es" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" LIBREOFFICE_EXTENSIONS="presenter-console presenter-minimizer" LLVM_TARGETS="AArch64 ARM RISCV WebAssembly" LUA_SINGLE_TARGET="lua5-1" LUA_TARGETS="lua5-1" OFFICE_IMPLEMENTATION="libreoffice" PHP_TARGETS="php7-3 php7-4" POSTGRES_TARGETS="postgres10 postgres11" PYTHON_SINGLE_TARGET="python3_8" PYTHON_TARGETS="python3_8" RUBY_TARGETS="ruby27 ruby30" SANE_BACKENDS="test" USERLAND="GNU" VIDEO_CARDS="nvidia" XTABLES_ADDONS="quota2 psd pknock lscan length2 ipv4options ipset ipp2p iface geoip fuzzy condition tee tarpit sysrq proto steal rawnat logmark ipmark dhcpmac delude chaos account" Unset: CC, CPPFLAGS, CTARGET, CXX, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LC_ALL, PORTAGE_BINHOST, PORTAGE_BUNZIP2_COMMAND, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS, PORTAGE_RSYNC_EXTRA_OPTS, RUSTFLAGS
Given that gcc is a multistage cross-compiler we need to have a way to distinguish CFLAGS_FOR_BUILD, CFLAGS_FOR_HOST and CFLAGS_FOR_TARGET. As we don't have a canonical way to do it eclass falls back to a set of safe values.
