From 5d511948cddee415c2f0f1103bda0468a193f2d6 Mon Sep 17 00:00:00 2001
From: Maria Matejka <mq@ucw.cz>
Date: Fri, 15 Mar 2019 15:07:00 +0100
Subject: [PATCH] Build: Automatic dependency tracking for generated files

---
 Makefile.in     | 44 +++++++++++++++++++++++++-------------------
 client/Makefile |  2 --
 conf/Makefile   |  3 ++-
 3 files changed, 27 insertions(+), 22 deletions(-)

diff --git a/Makefile.in b/Makefile.in
index 0ecd6811..98047e0c 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -65,7 +65,8 @@ endif
 docgoals := docs userdocs progdocs
 testgoals := check test tests tests_run
 cleangoals := clean distclean testsclean
-.PHONY: all daemon cli $(docgoals) $(testgoals) $(cleangoals) tags cscope
+.PHONY: all daemon cli $(docgoals) $(testgoals) $(cleangoals) tags cscope prepare
+
 all: daemon cli
 
 daemon: $(daemon)
@@ -103,35 +104,50 @@ include $(addsuffix /Makefile,$(addprefix $(srcdir)/,$(dirs)))
 
 # Generic rules
 # Object file rules
-$(objdir)/%.o: $(srcdir)/%.c $(objdir)/.dir-stamp $(objdir)/sysdep/paths.h
+$(objdir)/%.o: $(srcdir)/%.c | prepare
 	$(E)echo CC -o $@ -c $<
 	$(Q)$(CC) $(CFLAGS) -MMD -MP -o $@ -c $<
 
-$(objdir)/%.o: $(objdir)/%.c $(objdir)/.dir-stamp $(objdir)/sysdep/paths.h
+$(objdir)/%.o: $(objdir)/%.c | prepare
 	$(E)echo CC -o $@ -c $<
 	$(Q)$(CC) $(CFLAGS) -MMD -MP -o $@ -c $<
 
 # Debug: Preprocessed source rules
-$(objdir)/%.E: $(srcdir)/%.c $(objdir)/.dir-stamp $(objdir)/sysdep/paths.h
+$(objdir)/%.E: $(srcdir)/%.c | prepare
 	$(E)echo CC -o $@ -E $<
 	$(Q)$(CC) $(CFLAGS) -MMD -MP -o $@ -E $<
 
-$(objdir)/%.E: $(objdir)/%.c $(objdir)/.dir-stamp $(objdir)/sysdep/paths.h
+$(objdir)/%.E: $(objdir)/%.c | prepare
 	$(E)echo CC -o $@ -E $<
 	$(Q)$(CC) $(CFLAGS) -MMD -MP -o $@ -E $<
 
 # Debug: Assembler object rules
-$(objdir)/%.S: $(srcdir)/%.c $(objdir)/.dir-stamp $(objdir)/sysdep/paths.h
+$(objdir)/%.S: $(srcdir)/%.c | prepare
 	$(E)echo CC -o $@ -S $<
 	$(Q)$(CC) $(CFLAGS) -MMD -MP -o $@ -S $<
 
-$(objdir)/%.S: $(objdir)/%.c $(objdir)/.dir-stamp $(objdir)/sysdep/paths.h
+$(objdir)/%.S: $(objdir)/%.c | prepare
 	$(E)echo CC -o $@ -S $<
 	$(Q)$(CC) $(CFLAGS) -MMD -MP -o $@ -S $<
 
+# Finally include the computed dependencies:
+DEPS = $(shell find $(objdir) -name '*.d')
 
+# ## if there is at least one non-clean goal
+ifneq ($(filter-out $(cleangoals),$(MAKECMDGOALS)),)
+-include $(DEPS)
+endif
 
-$(objdir)/.dir-stamp:
+# ## if the implicit goal is called
+ifeq ($(MAKECMDGOALS),)
+-include $(DEPS)
+endif
+
+# Rule for pre-generating all generated includables
+# before compiling any C file
+prepare: $(objdir)/sysdep/paths.h | $(objdir)/.dir-stamp
+
+$(objdir)/.dir-stamp: Makefile
 	$(E)echo MKDIR -p $(addprefix $(objdir)/,$(dirs) doc)
 	$(Q)mkdir -p $(addprefix $(objdir)/,$(dirs) doc)
 	$(Q)touch $@
@@ -150,7 +166,7 @@ $(objdir)/sysdep/paths.h: Makefile
 
 tests_targets_ok = $(addsuffix .ok,$(tests_targets))
 
-$(tests_targets): %: %.o $(tests_objs)
+$(tests_targets): %: %.o $(tests_objs) | prepare
 	$(E)echo LD $(LDFLAGS) -o $@ $< "..." $(LIBS)
 	$(Q)$(CC) $(LDFLAGS) -o $@ $^ $(LIBS)
 
@@ -165,16 +181,6 @@ check: tests tests_run
 tests: $(tests_targets)
 tests_run: $(tests_targets_ok)
 
-# Finally include the computed dependencies
-
-ifneq ($(filter-out $(cleangoals),$(MAKECMDGOALS)),)
--include $(shell find $(objdir) -name "*.d")
-endif
-
-ifeq ($(MAKECMDGOALS),)
--include $(shell find $(objdir) -name "*.d")
-endif
-
 tags:
 	cd $(srcdir) ; etags -lc `find $(dirs) -name *.[chY]`
 
diff --git a/client/Makefile b/client/Makefile
index fccb8346..933ae9de 100644
--- a/client/Makefile
+++ b/client/Makefile
@@ -3,8 +3,6 @@ obj := $(src-o-files)
 
 $(all-client)
 
-$(o)commands.o: $(objdir)/conf/commands.h
-
 $(exedir)/birdc: $(o)birdc.o
 $(exedir)/birdc: LIBS += $(CLIENT_LIBS)
 
diff --git a/conf/Makefile b/conf/Makefile
index 984624b4..5c10bbcb 100644
--- a/conf/Makefile
+++ b/conf/Makefile
@@ -25,9 +25,10 @@ $(o)cf-parse.tab.c: $(o)cf-parse.y
 $(o)cf-lex.c: $(s)cf-lex.l
 	$(FLEX) $(FLEX_DEBUG) -f -s -B -8 -Pcf_ -o$@ $<
 
-$(o)cf-lex.o: $(o)cf-parse.tab.h $(o)keywords.h
 $(o)cf-lex.o: CFLAGS+=-Wno-sign-compare -Wno-unused-function
 
+prepare: $(o)keywords.h $(o)commands.h $(o)cf-parse.tab.h
+
 $(addprefix $(o), cf-parse.y keywords.h commands.h cf-parse.tab.h cf-parse.tab.c cf-lex.c): $(objdir)/.dir-stamp
 
 $(call clean,cf-parse.tab.h cf-parse.tab.c cf-parse.y keywords.h commands.h cf-lex.c cf-parse.output)