build: remove mkdir commands from build steps.

* Makefile (COMPILE_C_WITH_DEPS, WINDRES): Do not call mkdir.
(win/%.res): Express dependency on existence of win
subdirectory in the build directory. We use an order-only
prerequisite, so that timestamps are not compared.
We don't want to be rebuilding objects if the directory
they are in has a newer timestamp, which is often the case.
(OBJS): Extract the relative directory paths from $(OBJS),
and make each directory the target of a rule which creates it.
Then, make each target in $(OBJS) dependent (order-only) on
the directory into which it will be placed, so before that
object is built, the directory gets created with mkdir -p.

1 files changed, 8 insertions, 3 deletions

diff --git a/Makefile b/Makefile
index 350703ad..283b46cc 100644
--- a/Makefile
+++ b/Makefile
@@ -131,7 +131,6 @@ endef
 
 define COMPILE_C_WITH_DEPS
 $(call ABBREV,CC)
-$(call SH,mkdir -p $(dir $@))
 $(call SH,$(TXR_CC) -MMD -MT $@ $(1) $(TXR_CFLAGS) -c -o $@ $<)
 endef
 
@@ -142,7 +141,6 @@ endef
 
 define WINDRES
 $(call ABBREV,RES)
-$(call SH,mkdir -p $(dir $@))
 $(call SH,windres -O coff -DTXR_VER=$(txr_ver) $< $@)
 endef
 
@@ -187,7 +185,7 @@ dbg/%-win.o: $(top_srcdir)%.c
 opt/%-win.o: $(top_srcdir)%.c
 	$(call COMPILE_C_WITH_DEPS, $(OPT_FLAGS))
 
-win/%.res: $(top_srcdir)win/%.rc $(top_srcdir)win/%.ico
+win/%.res: $(top_srcdir)win/%.rc $(top_srcdir)win/%.ico | win
 	$(call WINDRES)
 
 %.tlo: %.tl | $(PROG)
@@ -249,6 +247,13 @@ dbg/lex.yy.o: lex.yy.c
 opt/y.tab.o: y.tab.c
 dbg/y.tab.o: y.tab.c
 
+# Turn each directory in the object file tree into target built by mkdir -p
+$(sort $(foreach name,$(OBJS),$(dir $(name)))) win:
+	$(call SH,mkdir -p $@)
+
+# Make each object file depend on its own directory, so that it's created.
+$(foreach obj,$(OBJS),$(eval $(obj): | $(dir $(obj))))
+
 ifeq ($(maintainer),y)
 
 lex.yy.c: $(top_srcdir)parser.l