What is gcc-config?

gcc-config allows Gentoo users to switch active gcc safely and allows querying facts about installed toolchains.

Usage

To switch active gcc while system runs:

    $ gcc-config x86_64-pc-linux-gnu-8.1.0
    $ gcc-config x86_64-pc-linux-gnu-7.2.0

Ideally changes should be visible instantly and atomically without shell restart.

To query where the real gcc binaries are hiding:

    $ gcc-config -B $(gcc-config -c)

To parse a profile into TARGET and toolchain version:

    $ gcc-config -S sparc64-unknown-linux-gnu-9.2.0

Files, variables, things.

• Wrappers (symlinks to compiler binary like /usr/${CTARGET}/gcc-bin/${GCC_VERSION}/gcc)

  /usr/bin/gcc (native)

  /usr/bin/g++ (native)

  /usr/bin/${CTARGET}-gcc (native and cross)

  ...

  (all files from /usr/${CTARGET}/gcc-bin/$GCC_VERSION/*)

  See gcc-config script for wrapping details.

  /usr/bin/c89 (native)

  /usr/bin/c99 (native)

• private gcc configs (provided by toolchain.eclass, gcc ebuilds)

  /etc/env.d/gcc/x86_64-pc-linux-gnu-8.1.0

Contains variables that describe toolchain layout:

          LDPATH="/usr/lib/gcc/x86_64-pc-linux-gnu/8.1.0"
          MANPATH="/usr/share/gcc-data/x86_64-pc-linux-gnu/8.1.0/man"
          INFOPATH="/usr/share/gcc-data/x86_64-pc-linux-gnu/8.1.0/info"
          STDCXX_INCDIR="g++-v8"
          CTARGET="x86_64-pc-linux-gnu"
          GCC_SPECS=""
          MULTIOSDIRS="../lib64"
          GCC_PATH="/usr/x86_64-pc-linux-gnu/gcc-bin/8.1.0"

  Used by `gcc-config` to generate wrappers and `05gcc-` `env.d` files.

• gcc env.d compiler entries (provided by gcc-config)

  /etc/env.d/04gcc-${CTARGET} (native)

  Populates paths for native-compilers
  

        GCC_SPECS=""
        MANPATH="/usr/share/gcc-data/x86_64-pc-linux-gnu/8.2.0/man"
        INFOPATH="/usr/share/gcc-data/x86_64-pc-linux-gnu/8.2.0/info"

Used by env-update to populate $PATH and more (TODO: remove $PATH population).

TODOs

• Write proper gcc-config manpage based on this readme to be more discoverable.

• Figure out symlink ownership story. Right now, symlinks don't belong to any package.

  See bug 626606.

Releasing

  $ release=2.3.1; git tag -a -s -m "release ${release}" v${release}; make dist PV=${release}
  $ git push --tags origin