Refactoring: Introduce distinct host and target rpath var setters.

Two line summary: Distinguish HOST_RPATH and TARGET_RPATH; added
RPATH_LINK_SEARCH; skip tests broken in stage1; general cleanup.

`HOST_RPATH_VAR$(1)_T_$(2)_H_$(3)` and `TARGET_RPATH_VAR$(1)_T_$(2)_H_$(3)`
both match the format of the old `RPATH_VAR$(1)_T_$(2)_H_$(3)` (which
is still being set the same way that it was before, to one of either
HOST/TARGET depending on what stage we are building).  Namely, the format
is <XXX>_RPATH_VAR = "<LD_LIB_PATH_ENVVAR>=<COLON_SEP_PATH_ENTRIES>"

What this commit does:

* Pass both of the (newly introduced) HOST and TARGET rpath setup vars
  to `maketest.py`

* Update `maketest.py` to no longer update the LD_LIBRARY_PATH itself
  Instead, it passes along the HOST and TARGET rpath setup vars in
  environment variables `HOST_RPATH_ENV` and `TARGET_RPATH_ENV`

* Also, pass the current stage number to maketest.py; it in turn
  passes it (via an env var) to run-make tests.

  This allows the run-make tests to selectively change behavior
  (e.g. turn themselves off) to deal with incompatibilities with
  e.g. stage1.

* Cleanup: Distinguish in tools.mk between the command to run (`RUN`)
  and the file to generate to drive that command (`RUN_BINFILE`).  The
  main thing this enables is that `RUN` can now setup the
  `TARGET_RPATH_ENV` without having to dirty up the runner code in
  each of the `run-make` Makefiles.

* Cleanup: Factored out commands to delete dylib/rlib into
  REMOVE_DYLIBS/REMOVE_RLIBS.

  There were places where we were only calling `rm $(call DYLIB,foo)`
  even though we really needed to get rid of the whole glob (at least
  based on alex's findings on #13753 that removing the symlink does not
  suffice).

  Therefore rather than peppering the code with the awkward
  `rm $(TMPDIR)/$(call DYLIB_GLOB,foo)`, I instead introduced a common
  `REMOVE_DYLIBS` user function that expands into that when called.
  After I adding an analogous `REMOVE_RLIBS`, I changed all of the
  existing calls that rm dylibs or rlibs to use these routines
  instead.

  Note that the latter is not a true refactoring since I may have
  changed cases where it was our intent to only remove the sym-link.
  (But if that is the case, then we need to more deeply investigate
  alex's findings on #13753 where the system was still dynamically
  loading up the non-symlinked libraries that it finds on the load
  path.)

* Added RPATH_LINK_SEARCH command and use it on Linux.

  On some platforms, namely Linux, when you have libboot.so that has
  its internal rpath set (to e.g. $(ORIGIN)/path/to/HOSTDIR), the
  linker still complains when you do the link step and it does not
  know where to find libraries that libboot.so depends upon that live
  in HOSTDIR (think e.g. librustuv.so).

  As far as I can tell, the GNU linker will consult the
  LD_LIBRARY_PATH as part of the linking process to find such
  libraries.  But if you want to be more careful and not override
  LD_LIBRARY_PATH for the `gcc` invocation, then you need some other
  way to tell the linker where it can find the libraries that
  libboot.so needs.  The solution to this on Linux is the
  `-Wl,-rpath-link` command line option.

  However, this command line option does not exist on Mac OS X, (which
  appears to be figuring out how to resolve the libboot.dylib
  dependency by some other means, perhaps by consulting the rpath
  setting within libboot.dylib).

  So, in order to abstract over this distinction, I added the
  RPATH_LINK_SEARCH macro to the run-make infrastructure and added
  calls to it where necessary to get Linux working.  On architectures
  other than Linux, the macro expands to nothing.

* Disable miscellaneous tests atop stage1.

* An especially interesting instance of the previous bullet point:
  Excuse regex from doing rustdoc tests atop stage1.

  This was a (nearly-) final step to get `make check-stage1` working
  again.

  The use of a special-case check for regex here is ugly but is
  analogous other similar checks for regex such as the one that landed
  in PR #13844.

  The way this is written, the user will get a reminder that
  doc-crate-regex is being skipped whenever their rules attempt to do
  the crate documentation tests.  This is deliberate: I want people
  running `make check-stage1` to be reminded about which cases are
  being skipped.  (But if such echo noise is considered offensive, it
  can obviously be removed.)

* Got windows working with the above changes.

  This portion of the commit is a cleanup revision of the (previously
  mentioned on try builds) re-architecting of how the LD_LIBRARY_PATH
  setup and extension is handled in order to accommodate Windows' (1.)
  use of `$PATH` for that purpose and (2.) use of spaces in `$PATH`
  entries (problematic for make and for interoperation with tools at
  the shell).

* In addition, since the code has been rearchitected to pass the
  HOST_RPATH_DIR/TARGET_RPATH_DIR rather than a whole sh
  environment-variable setting command, there is no need to for the
  convert_path_spec calls in maketest.py, which in fact were put in
  place to placate Windows but were now causing the Windows builds to
  fail.  Instead we just convert the paths to absolute paths just like
  all of the other path arguments.

Also, note for makefile hackers: apparently you cannot quote operands
to `ifeq` in Makefile (or at least, you need to be careful about
adding them, e.g. to only one side).

Author: pnkfelix

mk/main.mk

@@ -349,18 +349,45 @@ CFGFLAG$(1)_T_$(2)_H_$(3) = stage$(1)
 endef
 
 # Same macro/variables as above, but defined in a separate loop so it can use
-# all the varibles above for all archs. The RPATH_VAR setup sometimes needs to
+# all the variables above for all archs. The RPATH_VAR setup sometimes needs to
 # reach across triples to get things in order.
+#
+# Defines (with the standard $(1)_T_$(2)_H_$(3) suffix):
+# * `LD_LIBRARY_PATH_ENV_NAME`: the name for the key to use in the OS
+#   environment to access or extend the lookup path for dynamic
+#   libraries.  Note on Windows, that key is `$PATH`, and thus not
+#   only conflates programs with dynamic libraries, but also often
+#   contains spaces which confuse make.
+# * `LD_LIBRARY_PATH_ENV_HOSTDIR`: the entry to add to lookup path for the host
+# * `LD_LIBRARY_PATH_ENV_TARGETDIR`: the entry to add to lookup path for target
+# 
+# Below that, HOST_RPATH_VAR and TARGET_RPATH_VAR are defined in terms of the
+# above settings.
+# 
 define SREQ_CMDS
 
 ifeq ($$(OSTYPE_$(3)),apple-darwin)
-  RPATH_VAR$(1)_T_$(2)_H_$(3) := \
-      DYLD_LIBRARY_PATH="$$$$DYLD_LIBRARY_PATH:$$(CURDIR)/$$(HLIB$(1)_H_$(3))"
+  LD_LIBRARY_PATH_ENV_NAME$(1)_T_$(2)_H_$(3) := DYLD_LIBRARY_PATH
+else
+ifeq ($$(CFG_WINDOWSY_$(2)),1)
+  LD_LIBRARY_PATH_ENV_NAME$(1)_T_$(2)_H_$(3) := PATH
 else
-  RPATH_VAR$(1)_T_$(2)_H_$(3) := \
-      LD_LIBRARY_PATH="$$$$LD_LIBRARY_PATH:$$(CURDIR)/$$(HLIB$(1)_H_$(3))"
+  LD_LIBRARY_PATH_ENV_NAME$(1)_T_$(2)_H_$(3) := LD_LIBRARY_PATH
+endif
 endif
 
+LD_LIBRARY_PATH_ENV_HOSTDIR$(1)_T_$(2)_H_$(3) := \
+    $$(CURDIR)/$$(HLIB$(1)_H_$(3))
+LD_LIBRARY_PATH_ENV_TARGETDIR$(1)_T_$(2)_H_$(3) := \
+    $$(CURDIR)/$$(TLIB1_T_$(2)_H_$(CFG_BUILD))
+
+HOST_RPATH_VAR$(1)_T_$(2)_H_$(3) := \
+  $$(LD_LIBRARY_PATH_ENV_NAME$(1)_T_$(2)_H_$(3))=$$$$$$(LD_LIBRARY_PATH_ENV_NAME$(1)_T_$(2)_H_$(3)):$$(LD_LIBRARY_PATH_ENV_HOSTDIR$(1)_T_$(2)_H_$(3))
+TARGET_RPATH_VAR$(1)_T_$(2)_H_$(3) := \
+  $$(LD_LIBRARY_PATH_ENV_NAME$(1)_T_$(2)_H_$(3))=$$$$$$(LD_LIBRARY_PATH_ENV_NAME$(1)_T_$(2)_H_$(3)):$$(LD_LIBRARY_PATH_ENV_TARGETDIR$(1)_T_$(2)_H_$(3))
+
+RPATH_VAR$(1)_T_$(2)_H_$(3) := $$(HOST_RPATH_VAR$(1)_T_$(2)_H_$(3))
+
 # Pass --cfg stage0 only for the build->host part of stage0;
 # if you're building a cross config, the host->* parts are
 # effectively stage1, since it uses the just-built stage0.
@@ -376,13 +403,7 @@ ifeq ($(1),0)
 ifneq ($(strip $(CFG_BUILD)),$(strip $(3)))
 CFGFLAG$(1)_T_$(2)_H_$(3) = stage1
 
-ifeq ($$(OSTYPE_$(3)),apple-darwin)
-  RPATH_VAR$(1)_T_$(2)_H_$(3) := \
-      DYLD_LIBRARY_PATH="$$$$DYLD_LIBRARY_PATH:$$(CURDIR)/$$(TLIB1_T_$(2)_H_$(CFG_BUILD))"
-else
-  RPATH_VAR$(1)_T_$(2)_H_$(3) := \
-      LD_LIBRARY_PATH="$$$$LD_LIBRARY_PATH:$$(CURDIR)/$$(TLIB1_T_$(2)_H_$(CFG_BUILD))"
-endif
+RPATH_VAR$(1)_T_$(2)_H_$(3) := $$(TARGET_RPATH_VAR$(1)_T_$(2)_H_$(3))
 endif
 endif
 

mk/tests.mk

@@ -793,8 +793,27 @@ else
 CRATEDOCTESTDEP_$(1)_$(2)_$(3)_$(4) = $$(RSINPUTS_$(4))
 endif
 
+# (Issues #13732, #13983, #14000) The doc for the regex crate includes
+# uses of the `regex!` macro from the regex_macros crate.  There is
+# normally a dependence injected that makes the target's regex depend
+# upon the host's regex_macros (see #13845), but that dependency
+# injection is currently skipped for stage1 as a special case.
+#
+# Therefore, as a further special case, this conditional skips
+# attempting to run the doc tests for the regex crate atop stage1,
+# (since there is no regex_macros crate for the stage1 rustc to load).
+#
+# (Another approach for solving this would be to inject the desired
+# dependence for stage1 as well, by setting things up to generate a
+# regex_macros crate that was compatible with the stage1 rustc and
+# thus re-enable our ability to run this test.)
+ifeq (stage$(1)-crate-$(4),stage1-crate-regex)
+check-stage$(1)-T-$(2)-H-$(3)-doc-crate-$(4)-exec:
+	@$$(call E, skipping doc-crate-$(4) as it uses macros and cannot run at stage$(1))
+else
 check-stage$(1)-T-$(2)-H-$(3)-doc-crate-$(4)-exec: \
 	$$(call TEST_OK_FILE,$(1),$(2),$(3),doc-crate-$(4))
+endif
 
 ifeq ($(2),$$(CFG_BUILD))
 $$(call TEST_OK_FILE,$(1),$(2),$(3),doc-crate-$(4)): $$(CRATEDOCTESTDEP_$(1)_$(2)_$(3)_$(4))
@@ -951,7 +970,10 @@ $(3)/test/run-make/%-$(1)-T-$(2)-H-$(3).ok: \
 	    "$$(CC_$(3)) $$(CFG_GCCISH_CFLAGS_$(3))" \
 	    $$(HBIN$(1)_H_$(3))/rustdoc$$(X_$(3)) \
 	    "$$(TESTNAME)" \
-	    "$$(RPATH_VAR$(1)_T_$(2)_H_$(3))"
+	    $$(LD_LIBRARY_PATH_ENV_NAME$(1)_T_$(2)_H_$(3)) \
+	    "$$(LD_LIBRARY_PATH_ENV_HOSTDIR$(1)_T_$(2)_H_$(3))" \
+	    "$$(LD_LIBRARY_PATH_ENV_TARGETDIR$(1)_T_$(2)_H_$(3))" \
+	    $(1)
 	@touch $$@
 else
 # FIXME #11094 - The above rule doesn't work right for multiple targets

src/etc/maketest.py

@@ -30,20 +30,21 @@ def putenv(name, value):
         value = normalize_path(value)
     os.putenv(name, value)
 
+def convert_path_spec(name, value):
+    if os.name == 'nt' and name != 'PATH':
+        value = ":".join(normalize_path(v) for v in value.split(";"))
+    return value
 
 make = sys.argv[2]
 putenv('RUSTC', os.path.abspath(sys.argv[3]))
 putenv('TMPDIR', os.path.abspath(sys.argv[4]))
 putenv('CC', sys.argv[5])
 putenv('RUSTDOC', os.path.abspath(sys.argv[6]))
 filt = sys.argv[7]
-ldpath = sys.argv[8]
-if ldpath != '':
-    name = ldpath.split('=')[0]
-    value = ldpath.split('=')[1]
-    if os.name == 'nt' and name != 'PATH':
-        value = ":".join(normalize_path(v) for v in value.split(";"))
-    os.putenv(name, value)
+putenv('LD_LIB_PATH_ENVVAR', sys.argv[8]);
+putenv('HOST_RPATH_DIR', os.path.abspath(sys.argv[9]));
+putenv('TARGET_RPATH_DIR', os.path.abspath(sys.argv[10]));
+putenv('RUST_BUILD_STAGE', sys.argv[11])
 
 if not filt in sys.argv[1]:
     sys.exit(0)

src/test/run-make/bootstrap-from-c-with-green/Makefile

@@ -1,9 +1,13 @@
 -include ../tools.mk
 
+HOST_LIB_DIR=$(TMPDIR)/../../../stage$(RUST_BUILD_STAGE)/lib
+# This overrides the LD_LIBRARY_PATH for RUN
+TARGET_RPATH_DIR:=$(TARGET_RPATH_DIR):$(TMPDIR)
+
 all:
 	$(RUSTC) lib.rs
 	ln -nsf $(call DYLIB,boot-*) $(call DYLIB,boot)
-	$(CC) main.c -o $(call RUN,main) -lboot
+	$(CC) main.c -o $(call RUN_BINFILE,main) $(call RPATH_LINK_SEARCH,$(HOST_LIB_DIR)) -lboot
 	$(call RUN,main)
-	rm $(call DYLIB,boot)
+	$(call REMOVE_DYLIBS,boot)
 	$(call FAIL,main)

src/test/run-make/bootstrap-from-c-with-native/Makefile

@@ -1,9 +1,13 @@
 -include ../tools.mk
 
+HOST_LIB_DIR=$(TMPDIR)/../../../stage$(RUST_BUILD_STAGE)/lib
+# This overrides the LD_LIBRARY_PATH for RUN
+TARGET_RPATH_DIR:=$(TARGET_RPATH_DIR):$(TMPDIR)
+
 all:
 	$(RUSTC) lib.rs
 	ln -nsf $(call DYLIB,boot-*) $(call DYLIB,boot)
-	$(CC) main.c -o $(call RUN,main) -lboot
+	$(CC) main.c -o $(call RUN_BINFILE,main) $(call RPATH_LINK_SEARCH,$(HOST_LIB_DIR)) -lboot
 	$(call RUN,main)
-	rm $(call DYLIB,boot)
+	$(call REMOVE_DYLIBS,boot)
 	$(call FAIL,main)

src/test/run-make/c-dynamic-dylib/Makefile

@@ -9,6 +9,6 @@ all: $(call DYLIB,cfoo)
 	$(RUSTC) foo.rs
 	$(RUSTC) bar.rs
 	$(call RUN,bar)
-	rm $(TMPDIR)/$(call DYLIB_GLOB,cfoo)
+	$(call REMOVE_DYLIBS,cfoo)
 	$(call FAIL,bar)
 endif

src/test/run-make/c-dynamic-rlib/Makefile

@@ -1,5 +1,8 @@
 -include ../tools.mk
 
+# This overrides the LD_LIBRARY_PATH for RUN
+TARGET_RPATH_DIR:=$(TARGET_RPATH_DIR):$(TMPDIR)
+
 # This hits an assertion in the linker on older versions of osx apparently
 ifeq ($(shell uname),Darwin)
 all:
@@ -8,7 +11,7 @@ else
 all: $(call DYLIB,cfoo)
 	$(RUSTC) foo.rs
 	$(RUSTC) bar.rs
-	LD_LIBRARY_PATH=$(TMPDIR) $(call RUN,bar)
-	rm $(TMPDIR)/$(call DYLIB_GLOB,cfoo)
+	$(call RUN,bar)
+	$(call REMOVE_DYLIBS,cfoo)
 	$(call FAIL,bar)
 endif

src/test/run-make/c-link-to-rust-dylib/Makefile

@@ -1,9 +1,11 @@
 -include ../tools.mk
 
+HOST_LIB_DIR=$(TMPDIR)/../../../stage$(RUST_BUILD_STAGE)/lib
+
 all:
 	$(RUSTC) foo.rs
 	ln -s $(call DYLIB,foo-*) $(call DYLIB,foo)
-	$(CC) bar.c -lfoo -o $(call RUN,bar) -Wl,-rpath,$(TMPDIR)
+	$(CC) bar.c -lfoo -o $(call RUN_BINFILE,bar) $(call RPATH_LINK_SEARCH,$(HOST_LIB_DIR)) -Wl,-rpath,$(TMPDIR)
 	$(call RUN,bar)
-	rm $(call DYLIB,foo)
+	$(call REMOVE_DYLIBS,foo)
 	$(call FAIL,bar)

src/test/run-make/c-link-to-rust-staticlib/Makefile

@@ -11,7 +11,7 @@ ifneq ($(shell uname),FreeBSD)
 all:
 	$(RUSTC) foo.rs
 	ln -s $(call STATICLIB,foo-*) $(call STATICLIB,foo)
-	$(CC) bar.c -lfoo -o $(call RUN,bar) $(EXTRAFLAGS) -lstdc++
+	$(CC) bar.c -lfoo -o $(call RUN_BINFILE,bar) $(EXTRAFLAGS) -lstdc++
 	$(call RUN,bar)
 	rm $(call STATICLIB,foo*)
 	$(call RUN,bar)

src/test/run-make/c-static-dylib/Makefile

@@ -5,5 +5,5 @@ all: $(call STATICLIB,cfoo)
 	$(RUSTC) bar.rs
 	rm $(TMPDIR)/$(call STATICLIB_GLOB,cfoo)
 	$(call RUN,bar)
-	rm $(TMPDIR)/$(call DYLIB_GLOB,foo)
+	$(call REMOVE_DYLIBS,foo)
 	$(call FAIL,bar)

src/test/run-make/c-static-rlib/Makefile

@@ -3,6 +3,6 @@
 all: $(call STATICLIB,cfoo)
 	$(RUSTC) foo.rs
 	$(RUSTC) bar.rs
-	rm $(TMPDIR)/$(call RLIB_GLOB,foo)
+	$(call REMOVE_RLIBS,foo)
 	rm $(TMPDIR)/$(call STATICLIB_GLOB,cfoo)
 	$(call RUN,bar)

src/test/run-make/dylib-chain/Makefile

@@ -6,7 +6,7 @@ all:
 	$(RUSTC) m3.rs
 	$(RUSTC) m4.rs
 	$(call RUN,m4)
-	rm $(TMPDIR)/$(call DYLIB_GLOB,m1)
-	rm $(TMPDIR)/$(call DYLIB_GLOB,m2)
-	rm $(TMPDIR)/$(call DYLIB_GLOB,m3)
+	$(call REMOVE_DYLIBS,m1)
+	$(call REMOVE_DYLIBS,m2)
+	$(call REMOVE_DYLIBS,m3)
 	$(call FAIL,m4)

src/test/run-make/extern-fn-reachable/Makefile

@@ -1,5 +1,8 @@
 -include ../tools.mk
 
+# This overrides the LD_LIBRARY_PATH for RUN
+TARGET_RPATH_DIR:=$(TARGET_RPATH_DIR):$(TMPDIR)
+
 all:
 	$(RUSTC) dylib.rs -o $(TMPDIR)/libdylib.so
 	$(RUSTC) main.rs

src/test/run-make/lto-smoke-c/Makefile

@@ -19,5 +19,5 @@ CC := $(CC:-g=)
 all:
 	$(RUSTC) foo.rs -Z lto
 	ln -s $(call STATICLIB,foo-*) $(call STATICLIB,foo)
-	$(CC) bar.c -lfoo -o $(call RUN,bar) $(EXTRAFLAGS) -lstdc++
+	$(CC) bar.c -lfoo -o $(call RUN_BINFILE,bar) $(EXTRAFLAGS) -lstdc++
 	$(call RUN,bar)

src/test/run-make/lto-syntax-extension/Makefile

@@ -1,6 +1,18 @@
 -include ../tools.mk
 
-all:
+# This test attempts to use syntax extensions, which are known to be
+# incompatible with stage1 at the moment.
+
+ifeq ($(RUST_BUILD_STAGE),1)
+DOTEST=
+else
+DOTEST=dotest
+endif
+
+all: $(DOTEST)
+
+dotest:
+	env
 	$(RUSTC) lib.rs
 	$(RUSTC) main.rs -Z lto
 	$(call RUN,main)

src/test/run-make/missing-crate-dependency/Makefile

@@ -3,7 +3,7 @@
 all: 
 	$(RUSTC) --crate-type=rlib crateA.rs
 	$(RUSTC) --crate-type=rlib crateB.rs
-	rm $(TMPDIR)/$(call RLIB_GLOB,crateA)
+	$(call REMOVE_RLIBS,crateA)
 	# Ensure crateC fails to compile since dependency crateA is missing
 	$(RUSTC) crateC.rs 2>&1 | \
 		grep "error: can't find crate for \`crateA\` which \`crateB\` depends on"

src/test/run-make/mixing-libs/Makefile

@@ -5,5 +5,5 @@ all:
 	$(RUSTC) dylib.rs
 	$(RUSTC) rlib.rs --crate-type=dylib
 	$(RUSTC) dylib.rs
-	rm $(call DYLIB,rlib-*)
+	$(call REMOVE_DYLIBS,rlib)
 	$(RUSTC) prog.rs && exit 1 || exit 0

src/test/run-make/obey-crate-type-flag/Makefile

@@ -7,7 +7,7 @@
 # fail if an rlib was built
 all:
 	$(RUSTC) test.rs
-	rm $(TMPDIR)/$(call RLIB_GLOB,test)
-	rm $(TMPDIR)/$(call DYLIB_GLOB,test)
+	$(call REMOVE_RLIBS,test)
+	$(call REMOVE_DYLIBS,test)
 	$(RUSTC) --crate-type dylib test.rs
-	rm $(TMPDIR)/$(call RLIB_GLOB,test) && exit 1 || exit 0
+	$(call REMOVE_RLIBS,test) && exit 1 || exit 0

src/test/run-make/output-type-permutations/Makefile

@@ -2,8 +2,8 @@
 
 all:
 	$(RUSTC) foo.rs --crate-type=rlib,dylib,staticlib
-	rm $(TMPDIR)/$(call RLIB_GLOB,bar)
-	rm $(TMPDIR)/$(call DYLIB_GLOB,bar)
+	$(call REMOVE_RLIBS,bar)
+	$(call REMOVE_DYLIBS,bar)
 	rm $(TMPDIR)/$(call STATICLIB_GLOB,bar)
 	$(RUSTC) foo.rs --crate-type=bin
 	rm $(TMPDIR)/$(call BIN,bar)
@@ -41,4 +41,4 @@ all:
 	cmp $(TMPDIR)/foo.bc $(TMPDIR)/bar.bc
 	rm $(TMPDIR)/bar.bc
 	rm $(TMPDIR)/foo.bc
-	rm $(TMPDIR)/$(call RLIB_GLOB,bar)
+	$(call REMOVE_RLIBS,bar)

src/test/run-make/prefer-dylib/Makefile

@@ -5,4 +5,4 @@ all:
 	$(RUSTC) foo.rs -C prefer-dynamic
 	$(call RUN,foo)
 	rm $(TMPDIR)/*bar*
-	$(call FAILS,foo)
+	$(call FAIL,foo)

src/test/run-make/tools.mk

@@ -4,8 +4,20 @@ export DYLD_LIBRARY_PATH:=$(TMPDIR):$(DYLD_LIBRARY_PATH)
 RUSTC := $(RUSTC) --out-dir $(TMPDIR) -L $(TMPDIR)
 CC := $(CC) -L $(TMPDIR)
 
-RUN = $(TMPDIR)/$(1)
-FAILS = $(TMPDIR)/$(1) && exit 1 || exit 0
+# These deliberately use `=` and not `:=` so that client makefiles can
+# augment HOST_RPATH_DIR / TARGET_RPATH_DIR.
+HOST_RPATH_ENV = \
+    $(LD_LIB_PATH_ENVVAR)=$$$(LD_LIB_PATH_ENVVAR):$(HOST_RPATH_DIR)
+TARGET_RPATH_ENV = \
+    $(LD_LIB_PATH_ENVVAR)=$$$(LD_LIB_PATH_ENVVAR):$(TARGET_RPATH_DIR)
+
+# This is the name of the binary we will generate and run; use this
+# e.g. for `$(CC) -o $(RUN_BINFILE)`.
+RUN_BINFILE = $(TMPDIR)/$(1)
+
+# RUN and FAIL are basic way we will invoke the generated binary.  On
+# non-windows platforms, they set the LD_LIBRARY_PATH environment
+# variable before running the binary.
 
 RLIB_GLOB = lib$(1)*.rlib
 STATICLIB = $(TMPDIR)/lib$(1).a
@@ -18,20 +30,32 @@ IS_WINDOWS=1
 endif
 
 ifeq ($(UNAME),Darwin)
+RUN = $(TARGET_RPATH_ENV) $(RUN_BINFILE)
+FAIL = $(TARGET_RPATH_ENV) $(RUN_BINFILE) && exit 1 || exit 0
 DYLIB_GLOB = lib$(1)*.dylib
 DYLIB = $(TMPDIR)/lib$(1).dylib
+RPATH_LINK_SEARCH =
 else
 ifdef IS_WINDOWS
+RUN = PATH="$(PATH):$(TARGET_RPATH_DIR)" $(RUN_BINFILE)
+FAIL = PATH="$(PATH):$(TARGET_RPATH_DIR)" $(RUN_BINFILE) && exit 1 || exit 0
 DYLIB_GLOB = $(1)*.dll
 DYLIB = $(TMPDIR)/$(1).dll
 BIN = $(1).exe
-export PATH := $(PATH):$(LD_LIBRARY_PATH)
+RPATH_LINK_SEARCH =
+RUSTC := PATH="$(PATH):$(LD_LIBRARY_PATH)" $(RUSTC)
 else
+RUN = $(TARGET_RPATH_ENV) $(RUN_BINFILE)
+FAIL = $(TARGET_RPATH_ENV) $(RUN_BINFILE) && exit 1 || exit 0
 DYLIB_GLOB = lib$(1)*.so
 DYLIB = $(TMPDIR)/lib$(1).so
+RPATH_LINK_SEARCH = -Wl,-rpath-link=$(1)
 endif
 endif
 
+REMOVE_DYLIBS     = rm $(TMPDIR)/$(call DYLIB_GLOB,$(1))
+REMOVE_RLIBS      = rm $(TMPDIR)/$(call RLIB_GLOB,$(1))
+
 %.a: %.o
 	ar crus $@ $<
 %.dylib: %.o