Make build products depend on their target directories.

This is an attempt to address Issue #3326 by adding [*order-only*][1]
prerequsites of each build product on the directory where it is to go.
It is important that the prerequisites be order-only, since the
timestamp on a parent directory is not relevant to whether a product
is out of date; the parent directory merely needs to exist.

(This use case of generating target directories was provided as an
[example][2] of how order-only prequisites are used.)

[1]: http://www.gnu.org/software/make/manual/html_node/Prerequisite-Types.html

[2]: http://www.kolpackov.net/pipermail/notes/2004-January/000001.html

2 files changed, 45 insertions, 19 deletions

diff --git a/mk/host.mk b/mk/host.mk
index 13a8a540117..54e7e7ca096 100644
--- a/mk/host.mk
+++ b/mk/host.mk
@@ -29,7 +29,9 @@ $$(HBIN$(2)_H_$(4))/rustc$$(X_$(4)): \
 	$$(HLIB$(2)_H_$(4))/$(CFG_RUSTLLVM_$(4)) \
 	$$(HLIB$(2)_H_$(4))/$(CFG_LIBRUSTC_$(4)) \
 	$$(HCORELIB_DEFAULT$(2)_H_$(4)) \
-	$$(HSTDLIB_DEFAULT$(2)_H_$(4))
+	$$(HSTDLIB_DEFAULT$(2)_H_$(4)) \
+	| $$(HBIN$(2)_H_$(4))/
+
 	@$$(call E, cp: $$@)
 	$$(Q)cp $$< $$@
 
@@ -39,7 +41,9 @@ $$(HLIB$(2)_H_$(4))/$(CFG_LIBRUSTC_$(4)): \
 	$$(HLIB$(2)_H_$(4))/$(CFG_RUNTIME_$(4)) \
 	$$(HLIB$(2)_H_$(4))/$(CFG_RUSTLLVM_$(4)) \
 	$$(HCORELIB_DEFAULT$(2)_H_$(4)) \
-	$$(HSTDLIB_DEFAULT$(2)_H_$(4))
+	$$(HSTDLIB_DEFAULT$(2)_H_$(4)) \
+	| $$(HBIN$(2)_H_$(4))/
+
 	@$$(call E, cp: $$@)
 	$$(Q)cp $$< $$@
 	$$(Q)cp -R $$(TLIB$(1)_T_$(4)_H_$(3))/$(LIBRUSTC_GLOB_$(4)) \
@@ -51,7 +55,8 @@ $$(HLIB$(2)_H_$(4))/$(CFG_LIBSYNTAX_$(4)): \
 	$$(HLIB$(2)_H_$(4))/$(CFG_RUNTIME_$(4)) \
 	$$(HLIB$(2)_H_$(4))/$(CFG_RUSTLLVM_$(4)) \
 	$$(HCORELIB_DEFAULT$(2)_H_$(4)) \
-	$$(HSTDLIB_DEFAULT$(2)_H_$(4))
+	$$(HSTDLIB_DEFAULT$(2)_H_$(4)) \
+	| $$(HBIN$(2)_H_$(4))/
 	@$$(call E, cp: $$@)
 	$$(Q)cp $$< $$@
 	$$(Q)cp -R $$(TLIB$(1)_T_$(4)_H_$(3))/$(LIBSYNTAX_GLOB_$(4)) \
@@ -59,13 +64,15 @@ $$(HLIB$(2)_H_$(4))/$(CFG_LIBSYNTAX_$(4)): \
 	        $$(HLIB$(2)_H_$(4))
 
 $$(HLIB$(2)_H_$(4))/$(CFG_RUNTIME_$(4)): \
-	$$(TLIB$(1)_T_$(4)_H_$(3))/$(CFG_RUNTIME_$(4))
+	$$(TLIB$(1)_T_$(4)_H_$(3))/$(CFG_RUNTIME_$(4)) \
+	| $$(HBIN$(2)_H_$(4))/
 	@$$(call E, cp: $$@)
 	$$(Q)cp $$< $$@
 
 $$(HLIB$(2)_H_$(4))/$(CFG_CORELIB_$(4)): \
 	$$(TLIB$(1)_T_$(4)_H_$(3))/$(CFG_CORELIB_$(4)) \
-	$$(HLIB$(2)_H_$(4))/$(CFG_RUNTIME_$(4))
+	$$(HLIB$(2)_H_$(4))/$(CFG_RUNTIME_$(4)) \
+	| $$(HBIN$(2)_H_$(4))/
 	@$$(call E, cp: $$@)
 	$$(Q)cp $$< $$@
 # Subtle: We do not let the shell expand $(CORELIB_DSYM_GLOB) directly rather
@@ -82,7 +89,8 @@ $$(HLIB$(2)_H_$(4))/$(CFG_CORELIB_$(4)): \
 $$(HLIB$(2)_H_$(4))/$(CFG_STDLIB_$(4)): \
 	$$(TLIB$(1)_T_$(4)_H_$(3))/$(CFG_STDLIB_$(4)) \
 	$$(HLIB$(2)_H_$(4))/$(CFG_CORELIB_$(4)) \
-	$$(HLIB$(2)_H_$(4))/$(CFG_RUNTIME_$(4))
+	$$(HLIB$(2)_H_$(4))/$(CFG_RUNTIME_$(4)) \
+	| $$(HBIN$(2)_H_$(4))/
 	@$$(call E, cp: $$@)
 	$$(Q)cp $$< $$@
 	$$(Q)cp -R $$(TLIB$(1)_T_$(4)_H_$(3))/$(STDLIB_GLOB_$(4)) \
@@ -91,14 +99,16 @@ $$(HLIB$(2)_H_$(4))/$(CFG_STDLIB_$(4)): \
 
 $$(HLIB$(2)_H_$(4))/libcore.rlib: \
 	$$(TLIB$(1)_T_$(4)_H_$(3))/libcore.rlib \
-	$$(HLIB$(2)_H_$(4))/$$(CFG_RUNTIME_$(4))
+	$$(HLIB$(2)_H_$(4))/$$(CFG_RUNTIME_$(4)) \
+	| $$(HBIN$(2)_H_$(4))/
 	@$$(call E, cp: $$@)
 	$$(Q)cp $$< $$@
 
 $$(HLIB$(2)_H_$(4))/libstd.rlib: \
 	$$(TLIB$(1)_T_$(4)_H_$(3))/libstd.rlib \
 	$$(HLIB$(2)_H_$(4))/libcore.rlib \
-	$$(HLIB$(2)_H_$(4))/$$(CFG_RUNTIME_$(4))
+	$$(HLIB$(2)_H_$(4))/$$(CFG_RUNTIME_$(4)) \
+	| $$(HBIN$(2)_H_$(4))/
 	@$$(call E, cp: $$@)
 	$$(Q)cp $$< $$@
 
@@ -106,15 +116,20 @@ $$(HLIB$(2)_H_$(4))/librustc.rlib: \
 	$$(TLIB$(1)_T_$(4)_H_$(3))/librustc.rlib \
 	$$(HLIB$(2)_H_$(4))/libcore.rlib \
 	$$(HLIB$(2)_H_$(4))/libstd.rlib \
-	$$(HLIB$(2)_H_$(4))/$$(CFG_RUNTIME_$(4))
+	$$(HLIB$(2)_H_$(4))/$$(CFG_RUNTIME_$(4)) \
+	| $$(HBIN$(2)_H_$(4))/
 	@$$(call E, cp: $$@)
 	$$(Q)cp $$< $$@
 
 $$(HLIB$(2)_H_$(4))/$(CFG_RUSTLLVM_$(4)): \
-	$$(TLIB$(1)_T_$(4)_H_$(3))/$(CFG_RUSTLLVM_$(4))
+	$$(TLIB$(1)_T_$(4)_H_$(3))/$(CFG_RUSTLLVM_$(4)) \
+	| $$(HBIN$(2)_H_$(4))/
 	@$$(call E, cp: $$@)
 	$$(Q)cp $$< $$@
 
+$$(HBIN$(2)_H_$(4))/:
+	mkdir -p $@
+
 endef
 
 $(foreach t,$(CFG_HOST_TRIPLES),					\
diff --git a/mk/target.mk b/mk/target.mk
index fba1a6e0ee5..a3e5a5caff1 100644
--- a/mk/target.mk
+++ b/mk/target.mk
@@ -18,25 +18,29 @@
 define TARGET_STAGE_N
 
 $$(TLIB$(1)_T_$(2)_H_$(3))/libmorestack.a: \
-		rt/$(2)/arch/$$(HOST_$(2))/libmorestack.a
+		rt/$(2)/arch/$$(HOST_$(2))/libmorestack.a \
+		| $$(TLIB$(1)_T_$(2)_H_$(3))/
 	@$$(call E, cp: $$@)
 	$$(Q)cp $$< $$@
 
 $$(TLIB$(1)_T_$(2)_H_$(3))/$(CFG_RUNTIME_$(2)): \
-		rt/$(2)/$(CFG_RUNTIME_$(2))
+		rt/$(2)/$(CFG_RUNTIME_$(2)) \
+		| $$(TLIB$(1)_T_$(2)_H_$(3))/
 	@$$(call E, cp: $$@)
 	$$(Q)cp $$< $$@
 
 $$(TLIB$(1)_T_$(2)_H_$(3))/$(CFG_CORELIB_$(2)): \
 		$$(CORELIB_CRATE) $$(CORELIB_INPUTS) \
-		$$(TSREQ$(1)_T_$(2)_H_$(3))
+		$$(TSREQ$(1)_T_$(2)_H_$(3)) \
+		| $$(TLIB$(1)_T_$(2)_H_$(3))/
 	@$$(call E, compile_and_link: $$@)
 	$$(STAGE$(1)_T_$(2)_H_$(3)) -o $$@ $$< && touch $$@
 
 $$(TLIB$(1)_T_$(2)_H_$(3))/$(CFG_STDLIB_$(2)): \
 		$$(STDLIB_CRATE) $$(STDLIB_INPUTS) \
 	        $$(TLIB$(1)_T_$(2)_H_$(3))/$(CFG_CORELIB_$(2)) \
-		$$(TSREQ$(1)_T_$(2)_H_$(3))
+		$$(TSREQ$(1)_T_$(2)_H_$(3)) \
+		| $$(TLIB$(1)_T_$(2)_H_$(3))/
 	@$$(call E, compile_and_link: $$@)
 	$$(STAGE$(1)_T_$(2)_H_$(3)) -o $$@ $$< && touch $$@
 
@@ -44,7 +48,8 @@ $$(TLIB$(1)_T_$(2)_H_$(3))/$(CFG_LIBSYNTAX_$(3)): \
                 $$(LIBSYNTAX_CRATE) $$(LIBSYNTAX_INPUTS) \
 		$$(TSREQ$(1)_T_$(2)_H_$(3))			\
 		$$(TCORELIB_DEFAULT$(1)_T_$(2)_H_$(3))      \
-		$$(TSTDLIB_DEFAULT$(1)_T_$(2)_H_$(3))
+		$$(TSTDLIB_DEFAULT$(1)_T_$(2)_H_$(3)) \
+		| $$(TLIB$(1)_T_$(2)_H_$(3))/
 	@$$(call E, compile_and_link: $$@)
 	$$(STAGE$(1)_T_$(2)_H_$(3)) $(BORROWCK) -o $$@ $$< && touch $$@
 
@@ -52,20 +57,23 @@ $$(TLIB$(1)_T_$(2)_H_$(3))/$(CFG_LIBSYNTAX_$(3)): \
 ifneq ($$(findstring $(2),$$(CFG_HOST_TRIPLES)),)
 
 $$(TLIB$(1)_T_$(2)_H_$(3))/$(CFG_RUSTLLVM_$(3)): \
-		rustllvm/$(2)/$(CFG_RUSTLLVM_$(3))
+		rustllvm/$(2)/$(CFG_RUSTLLVM_$(3)) \
+		| $$(TLIB$(1)_T_$(2)_H_$(3))/
 	@$$(call E, cp: $$@)
 	$$(Q)cp $$< $$@
 
 $$(TLIB$(1)_T_$(2)_H_$(3))/$(CFG_LIBRUSTC_$(3)):		\
 		$$(COMPILER_CRATE) $$(COMPILER_INPUTS)		\
                 $$(TLIB$(1)_T_$(2)_H_$(3))/$(CFG_LIBSYNTAX_$(3)) \
-                $$(TLIB$(1)_T_$(2)_H_$(3))/$(CFG_RUSTLLVM_$(3))
+                $$(TLIB$(1)_T_$(2)_H_$(3))/$(CFG_RUSTLLVM_$(3)) \
+		| $$(TLIB$(1)_T_$(2)_H_$(3))/
 	@$$(call E, compile_and_link: $$@)
 	$$(STAGE$(1)_T_$(2)_H_$(3)) -o $$@ $$< && touch $$@
 
 $$(TBIN$(1)_T_$(2)_H_$(3))/rustc$$(X_$(3)):			\
-		$$(DRIVER_CRATE) 							\
-		$$(TLIB$(1)_T_$(2)_H_$(3))/$(CFG_LIBRUSTC_$(3))
+		$$(DRIVER_CRATE)				\
+		$$(TLIB$(1)_T_$(2)_H_$(3))/$(CFG_LIBRUSTC_$(3)) \
+		| $$(TLIB$(1)_T_$(2)_H_$(3))/
 	@$$(call E, compile_and_link: $$@)
 	$$(STAGE$(1)_T_$(2)_H_$(3)) --cfg rustc -o $$@ $$<
 ifdef CFG_ENABLE_PAX_FLAGS
@@ -75,6 +83,9 @@ endif
 
 endif
 
+$$(TLIB$(1)_T_$(2)_H_$(3))/:
+	mkdir -p $@
+
 endef
 
 # In principle, each host can build each target: