3534

Streamline the build process.

It's safest to always:
  a) check if each output is `older_than` the inputs necessary to
  construct it, and
  b) update the output only if something changed.

However:

  i) We don't yet have helpers to do b) in all situations, and
  ii) combining a) and b) can cause `older_than` to spuriously report
  files being updated.

So we'll always run exactly one of a) and b) and err on the side of
keeping the output reliable, at the risk of occasionally updating a file
unnecessarily and triggering unnecessary work downstream. Cross that
bridge when we run into it.

1 files changed, 22 insertions, 33 deletions

diff --git a/build b/build
index d3dc4b0a..dfd0fd81 100755
--- a/build
+++ b/build
@@ -11,6 +11,14 @@ set -e  # stop immediately on error
 # non-zero exit status only on error during building
 UNTIL_LAYER=${2:-zzz}
 
+# there's two mechanisms for fast builds here:
+# - if a command is quick to run, always run it but update the result only on any change
+# - otherwise run it only if the output is 'older_than' the inputs
+#
+# avoid combining both mechanisms for 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 $CC || export CC=cc
 test $CFLAGS || export CFLAGS="-g -O3"
@@ -71,22 +79,14 @@ older_than enumerate/enumerate enumerate/enumerate.cc && {
 (
   older_than tangle/tangle tangle/*.cc && {
     noisy_cd tangle
-      older_than type_list [0-9]*.cc && {
+      {
         grep -h "^struct .* {" [0-9]*.cc |sed 's/\(struct *[^ ]*\).*/\1;/'
         grep -h "^typedef " [0-9]*.cc
       } |update type_list
-      older_than function_list [0-9]*.cc && {
-        grep -h "^[^ #].*) {" [0-9]*.cc |sed 's/ {.*/;/' |update function_list
-      }
-      older_than file_list [0-9]*.cc && {
-        ls [0-9]*.cc |grep -v "\.test\.cc$" |sed 's/.*/#include "&"/' |update file_list
-      }
-      older_than test_file_list [0-9]*.test.cc && {
-        ls [0-9]*.test.cc |sed 's/.*/#include "&"/' |update test_file_list
-      }
-      older_than test_list [0-9]*.cc && {
-        grep -h "^[[:space:]]*void test_" [0-9]*.cc |sed 's/^\s*void \(.*\)() {$/\1,/' |update test_list
-      }
+      grep -h "^[^ #].*) {" [0-9]*.cc |sed 's/ {.*/;/' |update function_list
+      ls [0-9]*.cc |grep -v "\.test\.cc$" |sed 's/.*/#include "&"/' |update file_list
+      ls [0-9]*.test.cc |sed 's/.*/#include "&"/' |update test_file_list
+      grep -h "^[[:space:]]*void test_" [0-9]*.cc |sed 's/^\s*void \(.*\)() {$/\1,/' |update test_list
       $CXX $CFLAGS boot.cc -o tangle
     noisy_cd ..  # no effect; just to show us returning to the parent directory
   }
@@ -94,32 +94,23 @@ older_than enumerate/enumerate enumerate/enumerate.cc && {
 )
 
 LAYERS=$(./enumerate/enumerate --until $UNTIL_LAYER |grep -v '.mu$')
-older_than mu.cc $LAYERS enumerate/enumerate tangle/tangle && {
-  ./tangle/tangle $LAYERS |update mu.cc
-}
-older_than function_list mu.cc && {
-  grep -h "^[^[:space:]#].*) {$" mu.cc |grep -v ":.*(" |sed 's/ {.*/;/' |update function_list
-}
-older_than test_list mu.cc && {
-  grep -h "^\s*void test_" mu.cc |sed 's/^\s*void \(.*\)() {.*/\1,/' |update test_list
-}
+./tangle/tangle $LAYERS |update mu.cc
 
 older_than cleave/cleave cleave/cleave.cc && {
   $CXX -O3 -Wall -Wextra -fno-strict-aliasing cleave/cleave.cc -o cleave/cleave
   rm -rf .build
 }
 
+mkdir -p .build
+grep -h "^[^[:space:]#].*) {$" mu.cc |grep -v ":.*(" |sed 's/ {.*/;/' |update .build/function_list
+grep -h "^\s*void test_" mu.cc |sed 's/^\s*void \(.*\)() {.*/\1,/' |update .build/test_list
+mkdir -p .build/termbox
+update_cp termbox/termbox.h .build/termbox
+
 older_than mu_bin mu.cc *_list cleave/cleave termbox/* && {
-  mkdir -p .build
-  update_cp function_list .build
-  update_cp test_list .build
-  mkdir -p .build/termbox
-  cp termbox/termbox.h .build/termbox
   ./cleave/cleave mu.cc .build
   noisy_cd .build
-    older_than global_declarations_list global_definitions_list && {
-      grep ';' global_definitions_list |sed 's/[=(].*/;/' |sed 's/^[^\/# ]/extern &/' |sed 's/^extern extern /extern /' |update global_declarations_list
-    }
+    grep ';' global_definitions_list |sed 's/[=(].*/;/' |sed 's/^[^\/# ]/extern &/' |sed 's/^extern extern /extern /' |update global_declarations_list
     for f in mu_*.cc
     do
       older_than `echo $f |sed 's/\.cc$/.o/'` $f header global_declarations_list function_list test_list && {
@@ -144,8 +135,6 @@ older_than mu_bin mu.cc *_list cleave/cleave termbox/* && {
 ## [0-9]*.mu -> core.mu
 
 MU_LAYERS=$(./enumerate/enumerate --until $UNTIL_LAYER |grep '.mu$') || exit 0  # ok if no .mu files
-older_than core.mu $MU_LAYERS enumerate/enumerate && {
-  cat $MU_LAYERS |update core.mu
-}
+cat $MU_LAYERS |update core.mu
 
 exit 0