$NetBSD: README.mknative,v 1.23 2019/09/30 08:40:20 mrg Exp $

This file describes how to bootstrap the native toolchain on a new NetBSD
platform (and how to update the new toolchain files, if needed).  These
files may be generated on a cross-compile host without problems.

NOTE:  DO NOT RUN "mknative" BY HAND!  It requires the Makefile in this
directory to set up certain environments first.

Since libc's features change over time, the config.h files can change as a
result; thus the instructions below are the same no matter whether
bootstrapping on a cross or native host.  This is important: even on a
"native" host, you should bootstrap the toolchain by building from an
up-to-date source tree to a $DESTDIR using the exact same instructions.

In these notes, MACHINE is the $MACHINE of the target.  These files can be
cross-generated.  Though a $MACHINE_ARCH all uses the same config files, you
must pick a specific $MACHINE so that building the requisite bits below will
work.

0. Note that example paths like src/external/gpl3/gcc/lib/libgcc/arch will
   really be src/external/gpl3/gcc.old/lib/libgcc/arch for the previous GCC.

1. Set MKMAINTAINERTOOLS=yes in mk.conf.  (Needed so that src/tools/gettext
   gets built, eliciting proper HAVE_*GETTEXT* defns in config.h files.)

2. Build and install a cross toolchain (via "build.sh -m MACHINE tools").
   Note that while PR #47353 is not fixed, you can not use the -O option
   to build.sh. Use -M instead. (The differences are in layout and pathname
   prefixes in the object directory pointed to by each option.)

3. In src/tools/gcc, do "nbmake-MACHINE HAVE_GCC=8 bootstrap-libgcc".

   This will create just enough glue in src/external/gpl3/gcc/lib/libgcc/arch
   to make it possible to build, based on the toolchain built in
   ${.OBJDIR}/build.
   Because the files generated in this step contain things like
   -DCROSS_COMPILE, they are not suitable for committing.  Step 8 below
   will regenerate the "proper" libgcc config files.

4. At top level, do
   "nbmake-MACHINE obj do-distrib-dirs MKGCC=no MKBINUTILS=no HAVE_GCC=8", and
   "nbmake-MACHINE includes HAVE_GCC= MKGCC=no MKBINUTILS=no HAVE_GCC=8".
   (Note: replace 8 [for GCC 8.x] with the appropriate version you are going
   to mknative-for, the MKGCC=no prevents the standard makefiles from picking
   up any gcc version info automatically)

5. In src/lib/csu, do
   "nbmake-MACHINE dependall". and "nbmake-MACHINE install".

6. In src/external/gpl3/gcc/lib/libgcc, do
   "nbmake-MACHINE obj includes dependall install".

7. In each of src/external/lgpl3/gmp/lib/libgmp,
   src/external/lgpl3/mpfr/lib/libmpfr, src/external/lgpl3/mpc/lib/libmpc
   do "nbmake-MACHINE obj dependall".

8. In src/lib, do
   "nbmake-MACHINE dependall install MKGCC=no HAVE_GCC=8".

   Optionally, all of the following may be set in the environment to reduce
   the amount of code needed to build at this step.  Basically, it must be
   possible for static binaries to build and base system libs to exist so
   that "configure" can do its job for the target--these MK* options omit
   the rest for this stage of the build. 

   MKLINT=no
   MKPROFILE=no
   MKSHARE=no
   MKRUMP=no

9. In src/tools/gcc, do "nbmake-MACHINE native-gcc".

   This will do a full configury in ${.OBJDIR}/.native that is a "Canadian"
   cross toolchain (--build reflects the host platform, but --host and
   --target are the target).  The result is a tree that would build a
   native-to-NetBSD compiler on a cross host, and mknative pulls glue data
   from this.

10. Try out a full build using "nbmake-MACHINE"; the result should include
   a native compiler.

11. If all is well, commit the glue files added to src/gnu/{lib,usr.bin}/*.