7842 - new directory organization

Baremetal is now the default build target and therefore has its sources
at the top-level. Baremetal programs build using the phase-2 Mu toolchain
that requires a Linux kernel. This phase-2 codebase which used to be at
the top-level is now under the linux/ directory. Finally, the phase-2 toolchain,
while self-hosting, has a way to bootstrap from a C implementation, which
is now stored in linux/bootstrap. The bootstrap C implementation uses some
literate programming tools that are now in linux/bootstrap/tools.

So the whole thing has gotten inverted. Each directory should build one
artifact and include the main sources (along with standard library). Tools
used for building it are relegated to sub-directories, even though those
tools are often useful in their own right, and have had lots of interesting
programs written using them.

A couple of things have gotten dropped in this process:
  - I had old ways to run on just a Linux kernel, or with a Soso kernel.
    No more.
  - I had some old tooling for running a single test at the cursor. I haven't
    used that lately. Maybe I'll bring it back one day.

The reorg isn't done yet. Still to do:
  - redo documentation everywhere. All the README files, all other markdown,
    particularly vocabulary.md.
  - clean up how-to-run comments at the start of programs everywhere
  - rethink what to do with the html/ directory. Do we even want to keep
    supporting it?

In spite of these shortcomings, all the scripts at the top-level, linux/
and linux/bootstrap are working. The names of the scripts also feel reasonable.
This is a good milestone to take stock at.

1 files changed, 105 insertions, 0 deletions

diff --git a/linux/bootstrap/build b/linux/bootstrap/build
new file mode 100755
index 00000000..de5b432d
--- /dev/null
+++ b/linux/bootstrap/build
@@ -0,0 +1,105 @@
+#!/bin/sh
+# returns 0 on successful build or nothing to build
+# non-zero exit status only on error during building
+set -e  # stop immediately on error
+
+cd $(dirname $0)
+
+# [0-9]*.cc -> bootstrap.cc -> bootstrap_bin
+# (layers)   |               |
+#          tangle           $CXX
+
+# can also be called with a layer to only build until
+#   $ ./build --until 050
+UNTIL_LAYER=${2:-zzz}
+
+# we use two mechanisms to speed up rebuilds:
+# - older_than: run a command if the output is older than any of the inputs
+# - update: if a command is quick to run, always run it but update the result only on any change
+#
+# avoid combining both mechanisms to generate a single file
+# otherwise you'll see spurious messages about files being updated
+# risk: a file may unnecessarily update without changes, causing unnecessary work downstream
+
+test "$CXX" || export CXX=c++
+test "$CXXFLAGS" || export CXXFLAGS="-g -O3 -std=c++98"  # CI has an ancient version; don't expect recent dialects
+export CXXFLAGS="$CXXFLAGS -Wall -Wextra -fno-strict-aliasing"
+
+# return 1 if $1 is older than _any_ of the remaining args
+older_than() {
+  local target=$1
+  shift
+  if [ ! -e $target ]
+  then
+#?     echo "$target doesn't exist"
+    echo "updating $target" >&2
+    return 0  # success
+  fi
+  local f
+  for f in $*
+  do
+    if [ $f -nt $target ]
+    then
+      echo "updating $target" >&2
+      return 0  # success
+    fi
+  done
+  return 1  # failure
+}
+
+# redirect to $1, unless it's already identical
+update() {
+  if [ ! -e $1 ]
+  then
+    cat > $1
+  else
+    cat > $1.tmp
+    diff -q $1 $1.tmp >/dev/null  &&  rm $1.tmp  ||  mv $1.tmp $1
+  fi
+}
+
+update_cp() {
+  if [ ! -e $2/$1 ]
+  then
+    cp $1 $2
+  elif [ $1 -nt $2/$1 ]
+  then
+    cp $1 $2
+  fi
+}
+
+noisy_cd() {
+  cd $1
+  echo "-- `pwd`" >&2
+}
+
+older_than tools/enumerate tools/enumerate.cc && {
+  $CXX $CXXFLAGS tools/enumerate.cc -o tools/enumerate
+}
+
+older_than tools/tangle tools/tangle.cc && {
+  noisy_cd tools
+    grep -h "^[^ #].*) {" tangle.cc  |sed 's/ {.*/;/'  |update tangle.function_list
+    grep -h "^[[:space:]]*void test_" tangle.cc  |sed 's/^\s*void \(.*\)() {$/\1,/'  |update tangle.test_list
+    grep -h "^\s*void test_" tangle.cc  |sed 's/^\s*void \(.*\)() {.*/"\1",/'  |update tangle.test_name_list
+    $CXX $CXXFLAGS tangle.cc -o tangle
+    ./tangle test
+  noisy_cd ..  # no effect; just to show us returning to the parent directory
+}
+
+LAYERS=$(tools/enumerate --until $UNTIL_LAYER  |grep '.cc$')
+older_than bootstrap.cc $LAYERS tools/enumerate tools/tangle && {
+  # no update here; rely on 'update' calls downstream
+  tools/tangle $LAYERS  > bootstrap.cc
+}
+
+grep -h "^[^[:space:]#].*) {$" bootstrap.cc  |grep -v ":.*("  |sed 's/ {.*/;/'  |update function_list
+grep -h "^\s*void test_" bootstrap.cc  |sed 's/^\s*void \(.*\)() {.*/\1,/'  |update test_list
+grep -h "^\s*void test_" bootstrap.cc  |sed 's/^\s*void \(.*\)() {.*/"\1",/'  |update test_name_list
+
+older_than bootstrap_bin bootstrap.cc *_list && {
+  $CXX $CXXFLAGS bootstrap.cc -o bootstrap_bin
+  echo
+}
+
+exit 0