Experimental new redoconf C/C++ build/autoconfiguration system.

To test it out, try this:
	./do -j10 build
	cd docs/cookbook/c
	redo -j10 test

It should detect all the compilers on your system and make three
separate builds for each one: normal, debug, and optimized.  Then it
tries to run a test program under each one.

If there are windows cross compilers and you also have 'wine'
installed, it'll try running the test program under wine as well.

redoconf currently has no documentation other than the example program.
We'll fix that later.

redoconf/default.do.sh

@@ -0,0 +1,181 @@
+# This script starts with $PWD=output dir, $S=input dir.
+read -r S <src
+REDOCONF="$S/redoconf"
+if [ ! -d "$S" ] || [ ! -f "$REDOCONF/default.do.sh" ]; then
+	echo "default.do.sh: \$S is not set correctly." >&2
+	exit 99
+fi
+
+NL="
+"
+
+_mkdir_of() {
+	local dir="${1%/*}"
+	[ "$dir" = "$1" ] ||
+	[ -z "$dir" ] ||
+	[ -d "$dir" ] ||
+	mkdir -p "$dir"
+}
+
+# Delegate to .od files specifically for this target, if any.
+_base1=${1##*/}
+_dir1=${1%"$_base1"}
+_missing=""
+for d in "$S/$1.od" \
+         "$S/${_dir1}default.${_base1#*.}.od" \
+         "$REDOCONF/$1.od" \
+         "$REDOCONF/${_dir1}default.${_base1#*.}.od"; do
+	if [ -e "$d" ]; then
+		redo-ifchange "$d"
+		_mkdir_of "$3"
+		( PS4="$PS4[$d] "; . "$d" )
+		exit
+	else
+		missing="$missing$NL$d"
+	fi
+done
+
+_add_missing() {
+	[ -n "$missing" ] && (IFS="$NL"; set -f; redo-ifcreate $missing)
+	missing=
+}
+
+_pick_src() {
+	# Look for the source file corresponding to a given .o file.
+	# If the source file is missing, we can also build it from
+	# eg. a .c.do script.
+	#
+	# Returns the matching source file in $src, the compiler
+	# mode in $lang, and appends any redo-ifcreate targets to
+	# $missing.
+	lang=cc
+	for src in "$1.c"; do
+		[ -e "$src" ] && return
+		[ -e "$src.do" ] && return
+		missing="$missing$NL$src"
+	done
+	lang=cxx
+	for src in "$1.cc" "$1.cpp" "$1.cxx" "$1.C" "$1.c++"; do
+		[ -e "$src" ] && return
+		[ -e "$src.do" ] && return
+		missing="$missing$NL$src"
+	done
+	echo "default.do.sh: _pick_src: no source file found for '$1.*'" >&2
+	return 1
+}
+
+_objlist() {
+	local suffix="$1" list="$2" base="${2##*/}"
+	local dir="${2%"$base"}"
+	sed -Ee 's/\.(c|cc|cpp|cxx|C|c\+\+)$/'"$suffix/" <"$2" |
+	while read -r d; do
+		[ "$d" = "${d#-}" ] || continue
+		echo "$dir$d"
+	done
+}
+
+_flaglist() {
+	while read -r d; do
+		[ "$d" != "${d#-}" ] || continue
+		echo "$d"
+	done <"$1"
+}
+
+compile() {
+	redo-ifchange compile "$src" $dep
+	rm -f "$1.deps"
+	_mkdir_of "$3"
+	xCFLAGS="$xCFLAGS" PCH="$PCH" ./compile "$3" "$1.deps" "$src"
+	# TODO: make work with dependency filenames containing whitespace.
+	#   gcc writes whitespace-containing filenames with spaces
+	#   prefixed by backslash.  read (without -r) will remove the
+	#   backslashes but still use spaces for word splitting, so
+	#   it loses the distinction.  rc_splitwords() is the right
+	#   function, but currently has a max word limit.
+	read deps <"$2.deps"
+	redo-ifchange ${deps#*:}
+}
+
+case $1 in
+    *.fpic.o)
+	_pick_src "$S/${1%.fpic.o}"
+	_add_missing
+	xCFLAGS="-fPIC" PCH="2" dep="$lang-fpic.precompile" compile "$@"
+	exit  # fast path: exit as early as possible
+	;;
+    *.o)
+	_pick_src "$S/${1%.o}"
+	_add_missing
+	xCFLAGS="" PCH="1" dep="$lang.precompile" compile "$@"
+	exit  # fast path: exit as early as possible
+	;;
+    *.h.fpic.gch|*.hpp.fpic.gch)
+	src="$S/${1%.fpic.gch}"
+	xCFLAGS="-fPIC" PCH="" dep="" compile "$@"
+	# precompiled header is "unchanged" if its component
+	# headers are unchanged.
+	cat ${deps#*:} | tee $1.stamp | redo-stamp
+	;;
+    *.h.gch|*.hpp.gch)
+	src="$S/${1%.gch}"
+	xCFLAGS="" PCH="" dep="" compile "$@"
+	# precompiled header is "unchanged" if its component
+	# headers are unchanged.
+	cat ${deps#*:} | tee $1.stamp | redo-stamp
+	;;
+    *.a)
+	listf="${1%.a}.list"
+	redo-ifchange "$listf"
+	files=$(_objlist .o "$listf")
+	IFS="$NL"
+	redo-ifchange $files
+	ar q "$3" $files
+	;;
+    *.so)
+	verf="${1%.so}.ver"
+	listf="${1%.so}.list"
+	redo-ifchange link-shlib "$verf" "$listf"
+	read ver <"$verf"
+	files=$(_objlist .fpic.o "$listf")
+	xLIBS=$(_flaglist "$listf")
+	IFS="$NL"
+	redo-ifchange $files
+	xLIBS="$xLIBS" ./link-shlib "$1.$ver" $files
+	ln -s "$(basename "$1.$ver")" "$3"
+	ln -sf "$1.$ver" .
+	;;
+    *.list|*.ver)
+	if [ -e "$S/$1" ]; then
+		redo-ifchange "$S/$1"
+		_mkdir_of "$3"
+		cp "$S/$1" "$3"
+	else
+		echo "default.do.sh: no rule to build '$1'" >&2
+		exit 99
+	fi
+	;;
+    *)
+	# In unix, binary names typically don't have any special filename
+	# pattern, so we have to handle them in a catch-all here.
+	# We detect that it's intended as a binary, and not just a typo,
+	# by the existence of a .list or .list.od file with the same name,
+	# defining the list of input files.
+	#
+	# Some people like to name their binaries *.exe, eg. on Windows,
+	# even though that doesn't matter anymore, even on Windows.
+	# So use the same rules for generating a .exe as a non-.exe.
+	bin="${1%.exe}"
+	if [ -e "$S/$bin.list" -o -e "$S/$bin.list.od" ]; then
+		# a final program binary
+		redo-ifchange link "$bin.list"
+		files=$(_objlist .o "$bin.list")
+		xLIBS=$(_flaglist "$bin.list")
+		IFS="$NL"
+		redo-ifchange $files
+		xLIBS="$xLIBS" ./link "$3" $files
+	else
+		echo "default.do.sh: no rule to build '$1' or '$1.list'" >&2
+		exit 99
+	fi
+	;;
+esac