Update ab.

build/ab.mk

@@ -10,8 +10,12 @@ AR ?= ar
 CFLAGS ?= -g -Og
 LDFLAGS ?= -g
 PKG_CONFIG ?= pkg-config
+HOST_PKG_CONFIG ?= $(PKG_CONFIG)
 ECHO ?= echo
-TARGETS ?= +all
+CP ?= cp
+
+export PKG_CONFIG
+export HOST_PKG_CONFIG
 
 ifdef VERBOSE
 	hide =
@@ -23,11 +27,44 @@ else
 	endif
 endif
 
+WINDOWS := no
+OSX := no
+LINUX := no
+ifeq ($(OS),Windows_NT)
+    WINDOWS := yes
+else
+    UNAME_S := $(shell uname -s)
+    ifeq ($(UNAME_S),Linux)
+		LINUX := yes
+    endif
+    ifeq ($(UNAME_S),Darwin)
+		OSX := yes
+    endif
+endif
+
 ifeq ($(OS), Windows_NT)
 	EXT ?= .exe
 endif
 EXT ?=
 
+ifeq ($(PROGRESSINFO),)
+# The first make invocation here has to have its output discarded or else it
+# produces spurious 'Leaving directory' messages... don't know why.
+rulecount := $(strip $(shell $(MAKE) --no-print-directory -q $(OBJ)/build.mk PROGRESSINFO=1 > /dev/null \
+	&& $(MAKE) --no-print-directory -n $(MAKECMDGOALS) PROGRESSINFO=XXXPROGRESSINFOXXX | grep XXXPROGRESSINFOXXX | wc -l))
+ruleindex := 1
+PROGRESSINFO = "[$(ruleindex)/$(rulecount)]$(eval ruleindex := $(shell expr $(ruleindex) + 1))"
+endif
+
+PKG_CONFIG_HASHES = $(OBJ)/.pkg-config-hashes/target-$(word 1, $(shell $(PKG_CONFIG) --list-all | md5sum))
+HOST_PKG_CONFIG_HASHES = $(OBJ)/.pkg-config-hashes/host-$(word 1, $(shell $(HOST_PKG_CONFIG) --list-all | md5sum))
+
+$(OBJ)/build.mk : $(PKG_CONFIG_HASHES) $(HOST_PKG_CONFIG_HASHES)
+$(PKG_CONFIG_HASHES) $(HOST_PKG_CONFIG_HASHES) &:
+	$(hide) rm -rf $(OBJ)/.pkg-config-hashes
+	$(hide) mkdir -p $(OBJ)/.pkg-config-hashes
+	$(hide) touch $(PKG_CONFIG_HASHES) $(HOST_PKG_CONFIG_HASHES)
+
 include $(OBJ)/build.mk
 
 MAKEFLAGS += -r -j$(shell nproc)
@@ -47,8 +84,8 @@ clean::
 
 export PYTHONHASHSEED = 1
 build-files = $(shell find . -name 'build.py') $(wildcard build/*.py) $(wildcard config.py)
-$(OBJ)/build.mk: Makefile $(build-files)
+$(OBJ)/build.mk: Makefile $(build-files) build/ab.mk
 	@echo "AB"
 	@mkdir -p $(OBJ)
-	$(hide) $(PYTHON) -X pycache_prefix=$(OBJ) build/ab.py -o $@ build.py \
+	$(hide) $(PYTHON) -X pycache_prefix=$(OBJ)/__pycache__ build/ab.py -o $@ build.py \
 		|| rm -f $@

build/ab.py

@@ -16,6 +16,7 @@
 import inspect
 import string
 import sys
+import hashlib
 
 verbose = False
 quiet = False
@@ -147,12 +148,16 @@ def __init__(self, cwd, name):
         self.dir = join("$(OBJ)", name)
         self.ins = []
         self.outs = []
+        self.deps = []
         self.materialised = False
         self.args = {}
 
     def __eq__(self, other):
         return self.name is other.name
 
+    def __lt__(self, other):
+        return self.name < other.name
+
     def __hash__(self):
         return id(self)
 
@@ -313,7 +318,12 @@ def targetof(value, cwd=None):
             # Load the new build file.
 
             path = join(path, "build.py")
-            loadbuildfile(path)
+            try:
+                loadbuildfile(path)
+            except ModuleNotFoundError:
+                error(
+                    f"no such build file '{path}' while trying to resolve '{value}'"
+                )
             assert (
                 value in targets
             ), f"build file at '{path}' doesn't contain '+{target}' when trying to resolve '{value}'"
@@ -387,9 +397,12 @@ def filenameof(x):
     return xs[0]
 
 
-def emit(*args):
-    outputFp.write(" ".join(args))
-    outputFp.write("\n")
+def emit(*args, into=None):
+    s = " ".join(args) + "\n"
+    if into is not None:
+        into += [s]
+    else:
+        outputFp.write(s)
 
 
 def emit_rule(name, ins, outs, cmds=[], label=None):
@@ -398,26 +411,35 @@ def emit_rule(name, ins, outs, cmds=[], label=None):
     nonobjs = [f for f in fouts if not f.startswith("$(OBJ)")]
 
     emit("")
+
+    lines = []
     if nonobjs:
-        emit("clean::")
-        emit("\t$(hide) rm -f", *nonobjs)
+        emit("clean::", into=lines)
+        emit("\t$(hide) rm -f", *nonobjs, into=lines)
 
-    emit(".PHONY:", name)
+    emit(".PHONY:", name, into=lines)
     if outs:
-        emit(name, ":", *fouts)
-        if cmds:
-            emit(*fouts, "&:", *fins)
-        else:
-            emit(*fouts, ":", *fins)
+        emit(name, ":", *fouts, into=lines)
+        emit(*fouts, "&:" if len(fouts) > 1 else ":", *fins, "\x01", into=lines)
 
         if label:
-            emit("\t$(hide)", "$(ECHO)", label)
+            emit("\t$(hide)", "$(ECHO) $(PROGRESSINFO)", label, into=lines)
         for c in cmds:
-            emit("\t$(hide)", c)
+            emit("\t$(hide)", c, into=lines)
     else:
         assert len(cmds) == 0, "rules with no outputs cannot have commands"
-        emit(name, ":", *fins)
+        emit(name, ":", *fins, into=lines)
 
+    cmd = "".join(lines)
+    hash = hashlib.sha1(bytes(cmd, "utf-8")).hexdigest()
+
+    outputFp.write(cmd.replace("\x01", f"$(OBJ)/.hashes/{hash}"))
+
+    if outs:
+        emit(f"$(OBJ)/.hashes/{hash}:")
+        emit(
+            f"\t$(hide) mkdir -p $(OBJ)/.hashes && touch $(OBJ)/.hashes/{hash}"
+        )
     emit("")
 
 
@@ -451,7 +473,7 @@ def simplerule(
         name=self.name,
         ins=ins + deps,
         outs=outs,
-        label=self.templateexpand("{label} {name}"),
+        label=self.templateexpand("{label} {name}") if label else None,
         cmds=cs,
     )
 
@@ -476,8 +498,8 @@ def export(self, name=None, items: TargetsMap = {}, deps: Targets = []):
             cwd=self.cwd,
             ins=[srcs[0]],
             outs=[destf],
-            commands=["cp %s %s" % (srcs[0], destf)],
-            label="CP",
+            commands=["$(CP) %s %s" % (srcs[0], destf)],
+            label="",
         )
         subrule.materialise()