diff --git a/py/mkenv.mk b/py/mkenv.mk
new file mode 100644
index 0000000000..ed4e22096d
--- /dev/null
+++ b/py/mkenv.mk
@@ -0,0 +1,52 @@
+ifneq ($(lastword a b),b)
+$(error These Makefiles require make 3.81 or newer)
+endif
+
+# Set TOP to be the path to get from the current directory (where make was
+# invoked) to the top of the tree. $(lastword $(MAKEFILE_LIST)) returns
+# the name of this makefile relative to where make was invoked.
+#
+# We assume that this file is in the py directory so we use $(dir ) twice
+# to get to the top of the tree.
+
+THIS_MAKEFILE := $(lastword $(MAKEFILE_LIST))
+TOP := $(patsubst %/py/mkenv.mk,%,$(THIS_MAKEFILE))
+
+# Turn on increased build verbosity by defining BUILD_VERBOSE in your main
+# Makefile or in your environment. You can also use V=1 on the make command
+# line.
+
+ifeq ("$(origin V)", "command line")
+BUILD_VERBOSE=$(V)
+endif
+ifndef BUILD_VERBOSE
+BUILD_VERBOSE = 0
+endif
+ifeq ($(BUILD_VERBOSE),0)
+Q = @
+else
+Q =
+endif
+# Since this is a new feature, advertise it
+ifeq ($(BUILD_VERBOSE),0)
+$(info Use make V=1 or set BUILD_VERBOSE in your environment to increase build verbosity.)
+endif
+
+# default settings; can be overriden in main Makefile
+
+PY_SRC ?= $(TOP)/py
+BUILD ?= build
+
+RM = rm
+ECHO = @echo
+
+AS = $(CROSS_COMPILE)as
+CC = $(CROSS_COMPILE)gcc
+LD = $(CROSS_COMPILE)ld
+OBJCOPY = $(CROSS_COMPILE)objcopy
+SIZE = $(CROSS_COMPILE)size
+
+all:
+.PHONY: all
+
+MKENV_INCLUDED = 1
diff --git a/py/mkrules.mk b/py/mkrules.mk
new file mode 100644
index 0000000000..4c1ea08332
--- /dev/null
+++ b/py/mkrules.mk
@@ -0,0 +1,92 @@
+ifneq ($(MKENV_INCLUDED),1)
+# We assume that mkenv is in the same directory as this file.
+THIS_MAKEFILE = $(lastword $(MAKEFILE_LIST))
+include $(dir $(THIS_MAKEFILE))mkenv.mk
+endif
+
+# This file expects that OBJ contains a list of all of the object files.
+# The directory portion of each object file is used to locate the source
+# and should not contain any ..'s but rather be relative to the top of the 
+# tree.
+#
+# So for example, py/map.c would have an object file name py/map.o
+# The object files will go into the build directory and mantain the same
+# directory structure as the source tree. So the final dependency will look
+# like this:
+#
+# build/py/map.o: py/map.c
+#
+# We set vpath to point to the top of the tree so that the source files
+# can be located. By following this scheme, it allows a single build rule
+# to be used to compile all .c files.
+
+vpath %.S . $(TOP)
+$(BUILD)/%.o: %.S
+	$(ECHO) "CC $<"
+	$(Q)$(CC) $(CFLAGS) -c -o $@ $<
+
+vpath %.s . $(TOP)
+$(BUILD)/%.o: %.s
+	$(ECHO) "AS $<"
+	$(Q)$(AS) -o $@ $<
+
+define compile_c
+$(ECHO) "CC $<"
+$(Q)$(CC) $(CFLAGS) -c -MD -o $@ $<
+@# The following fixes the dependency file.
+@# See http://make.paulandlesley.org/autodep.html for details.
+@cp $(@:.o=.d) $(@:.o=.P); \
+  sed -e 's/#.*//' -e 's/^[^:]*: *//' -e 's/ *\\$$//' \
+      -e '/^$$/ d' -e 's/$$/ :/' < $(@:.o=.d) >> $(@:.o=.P); \
+  rm -f $(@:.o=.d)
+endef
+
+vpath %.c . $(TOP)
+$(BUILD)/%.o: %.c
+	$(call compile_c)
+
+# The following rule uses | to create an order only prereuisite. Order only
+# prerequisites only get built if they don't exist. They don't cause timestamp
+# checkng to be performed.
+#
+# $(sort $(var)) removes duplicates
+#
+# The net effect of this, is it causes the objects to depend on the
+# object directories (but only for existance), and the object directories
+# will be created if they don't exist.
+OBJ_DIRS = $(sort $(dir $(OBJ)))
+$(OBJ): | $(OBJ_DIRS)
+$(OBJ_DIRS):
+	mkdir -p $@
+
+ifneq ($(PROG),)
+# Build a standalone executable (unix and unix-cpy do this)
+
+all: $(PROG)
+
+$(PROG): $(OBJ)
+	$(ECHO) "LINK $<"
+	$(Q)$(CC) -o $@ $(OBJ) $(LIB) $(LDFLAGS)
+ifndef DEBUG
+	$(Q)strip $(PROG)
+endif
+	$(Q)size $(PROG)
+
+clean: clean-prog
+clean-prog:
+	$(RM) -f $(PROG)
+
+.PHONY: clean-prog
+endif
+
+clean:
+	$(RM) -rf $(BUILD)
+.PHONY: clean
+
+print-cfg:
+	$(ECHO) "PY_SRC = $(PY_SRC)"
+	$(ECHO) "BUILD  = $(BUILD)"
+	$(ECHO) "OBJ    = $(OBJ)"
+.PHONY: print-cfg
+
+-include $(OBJ:.o=.P)
diff --git a/py/py.mk b/py/py.mk
index 75394b3615..d4946e2838 100644
--- a/py/py.mk
+++ b/py/py.mk
@@ -1,48 +1,11 @@
-##########
-# The following should eventually go into a more central location
-# when a reorg is done.
-#
-# Turn on increased build verbosity by defining BUILD_VERBOSE in your main
-# Makefile or in your environment. You can also use V=1 on the make command
-# line.
-ifeq ("$(origin V)", "command line")
-BUILD_VERBOSE=$(V)
-endif
-ifndef BUILD_VERBOSE
-BUILD_VERBOSE = 0
-endif
-ifeq ($(BUILD_VERBOSE),0)
-Q = @
-else
-Q =
-endif
-# Since this is a new feature, advertise it
-ifeq ($(BUILD_VERBOSE),0)
-$(info Use make V=1 or set BUILD_VERBOSE in your environment to increase build verbosity.)
-endif
-#
-#########
-
-# default settings; can be overriden in main Makefile
-
-PY_SRC ?= ../py
-BUILD ?= build
-
-# to create the build directory
-
-$(BUILD):
-	$(Q)mkdir -p $@
-
 # where py object files go (they have a name prefix to prevent filename clashes)
-
-PY_BUILD = $(BUILD)/py.
+PY_BUILD = $(BUILD)/py
 
 # file containing qstr defs for the core Python bit
 
 PY_QSTR_DEFS = $(PY_SRC)/qstrdefs.h
 
 # py object files
-
 PY_O_BASENAME = \
 	nlrx86.o \
 	nlrx64.o \
@@ -108,50 +71,37 @@ PY_O_BASENAME = \
 	repl.o \
 
 # prepend the build destination prefix to the py object files
-
-PY_O = $(addprefix $(PY_BUILD), $(PY_O_BASENAME))
+PY_O = $(addprefix $(PY_BUILD)/, $(PY_O_BASENAME))
 
 # qstr data
 
-$(PY_BUILD)qstr.o: $(PY_BUILD)qstrdefs.generated.h
-
-$(PY_BUILD)qstrdefs.generated.h: $(PY_QSTR_DEFS) $(QSTR_DEFS) $(PY_SRC)/makeqstrdata.py
+# Adding an order only dependency on $(PY_BUILD) causes $(PY_BUILD) to get
+# created before we run the script to generate the .h
+$(PY_BUILD)/qstrdefs.generated.h: | $(PY_BUILD)
+$(PY_BUILD)/qstrdefs.generated.h: $(PY_QSTR_DEFS) $(QSTR_DEFS) $(PY_SRC)/makeqstrdata.py
 	$(ECHO) "makeqstrdata $(PY_QSTR_DEFS) $(QSTR_DEFS)"
 	$(Q)python $(PY_SRC)/makeqstrdata.py $(PY_QSTR_DEFS) $(QSTR_DEFS) > $@
 
-# emitters
-
-$(PY_BUILD)emitnx64.o: $(PY_SRC)/emitnative.c $(PY_SRC)/emit.h mpconfigport.h
-	$(ECHO) "CC $<"
-	$(Q)$(CC) $(CFLAGS) -DN_X64 -c -o $@ $<
+# We don't know which source files actually need the generated.h (since
+# it is #included from str.h). The compiler generated dependencies will cause
+# the right .o's to get recompiled if the generated.h file changes. Adding
+# an order-only dependendency to all of the .o's will cause the generated .h
+# to get built before we try to compile any of them.
+$(PY_O): | $(PY_BUILD)/qstrdefs.generated.h
 
-$(PY_BUILD)emitnthumb.o: $(PY_SRC)/emitnative.c $(PY_SRC)/emit.h mpconfigport.h
-	$(ECHO) "CC $<"
-	$(Q)$(CC) $(CFLAGS) -DN_THUMB -c -o $@ $<
-
-# general source files
+# emitters
 
-$(PY_BUILD)%.o: $(PY_SRC)/%.S
-	$(ECHO) "CC $<"
-	$(Q)$(CC) $(CFLAGS) -c -o $@ $<
+$(PY_BUILD)/emitnx64.o: CFLAGS += -DN_X64
+$(PY_BUILD)/emitnx64.o: py/emitnative.c
+	$(call compile_c)
 
-$(PY_BUILD)%.o: $(PY_SRC)/%.c mpconfigport.h $(PY_SRC)/qstr.h $(PY_QSTR_DEFS) $(QSTR_DEFS)
-	$(ECHO) "CC $<"
-	$(Q)$(CC) $(CFLAGS) -c -o $@ $<
+$(PY_BUILD)/emitnthumb.o: CFLAGS += -DN_THUMB
+$(PY_BUILD)/emitnthumb.o: py/emitnative.c
+	$(call compile_c)
 
 # optimising gc for speed; 5ms down to 4ms on pybv2
-$(PY_BUILD)gc.o: $(PY_SRC)/gc.c
-	$(ECHO) "CC $<"
-	$(Q)$(CC) $(CFLAGS) -O3 -c -o $@ $<
+$(PY_BUILD)gc.o: CFLAGS += -O3
 
 # optimising vm for speed, adds only a small amount to code size but makes a huge difference to speed (20% faster)
-$(PY_BUILD)vm.o: $(PY_SRC)/vm.c
-	$(ECHO) "CC $<"
-	$(Q)$(CC) $(CFLAGS) -O3 -c -o $@ $<
-
-# header dependencies
+$(PY_BUILD)vm.o: CFLAGS += -O3
 
-$(PY_BUILD)parse.o: $(PY_SRC)/grammar.h
-$(PY_BUILD)compile.o: $(PY_SRC)/grammar.h
-$(PY_BUILD)emitcpy.o: $(PY_SRC)/emit.h
-$(PY_BUILD)emitbc.o: $(PY_SRC)/emit.h
diff --git a/py/qstr.c b/py/qstr.c
index 268b3bafc9..f12cbceff6 100644
--- a/py/qstr.c
+++ b/py/qstr.c
@@ -55,7 +55,7 @@ const static qstr_pool_t const_pool = {
         (const byte*) "\0\0\0\0", // empty qstr
 #define Q(id, str) str,
 // TODO having 'build/' here is a bit of a hack, should take config variable from Makefile
-#include "build/py.qstrdefs.generated.h"
+#include "build/py/qstrdefs.generated.h"
 #undef Q
     },
 };
diff --git a/py/qstr.h b/py/qstr.h
index 271e2117c9..9224d48a19 100644
--- a/py/qstr.h
+++ b/py/qstr.h
@@ -9,7 +9,7 @@ enum {
     MP_QSTR_ = 1, // the empty qstr
 #define Q(id, str) MP_QSTR_##id,
 // TODO having 'build/py.' here is a bit of a hack, should take config variable from Makefile
-#include "build/py.qstrdefs.generated.h"
+#include "build/py/qstrdefs.generated.h"
 #undef Q
     MP_QSTR_number_of,
 } category_t;
diff --git a/stm/Makefile b/stm/Makefile
index 497fffa996..b3483e089d 100644
--- a/stm/Makefile
+++ b/stm/Makefile
@@ -1,5 +1,4 @@
-# define main target
-all: all2
+include ../py/mkenv.mk
 
 # qstr definitions (must come before including py.mk)
 QSTR_DEFS = qstrdefsport.h
@@ -7,10 +6,6 @@ QSTR_DEFS = qstrdefsport.h
 # include py core make definitions
 include ../py/py.mk
 
-# program for deletion
-RM = /bin/rm
-ECHO = @echo
-
 CMSIS=cmsis
 STMSRC=lib
 #STMOTGSRC=usbhost
@@ -18,11 +13,7 @@ FATFSSRC=fatfs
 CC3KSRC=cc3k
 DFU=../tools/dfu.py
 
-AS = arm-none-eabi-as
-CC = arm-none-eabi-gcc
-LD = arm-none-eabi-ld
-OBJCOPY = arm-none-eabi-objcopy
-SIZE = arm-none-eabi-size
+CROSS_COMPILE = arm-none-eabi-
 
 CFLAGS_CORTEX_M4 = -mthumb -mtune=cortex-m4 -mabi=aapcs-linux -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard -fsingle-precision-constant -Wdouble-promotion
 CFLAGS = -I. -I$(PY_SRC) -I$(FATFSSRC) -I$(CMSIS) -I$(STMSRC) -Wall -ansi -std=gnu99 $(CFLAGS_CORTEX_M4)
@@ -72,11 +63,12 @@ SRC_S = \
 	startup_stm32f40xx.s \
 	gchelper.s \
 
-SRC_FATFS = \
+SRC_FATFS = $(addprefix $(FATFSSRC)/,\
 	ff.c \
 	diskio.c \
+	)
 
-SRC_STM = \
+SRC_STM = $(addprefix $(STMSRC)/,\
 	stm32f4xx_rcc.c \
 	stm32f4xx_syscfg.c \
 	stm_misc.c \
@@ -112,8 +104,9 @@ SRC_STM = \
 	usbd_msc_data.c \
 	usbd_msc_scsi.c \
 	usbd_storage_msd.c \
+	)
 
-#SRC_STM_OTG = \
+#SRC_STM_OTG = $(addprefix $(STMSRC)/,\
 	usb_hcd.c \
 	usb_hcd_int.c \
 	usbh_core.c \
@@ -125,8 +118,9 @@ SRC_STM = \
 	usbh_hid_mouse.c \
 	usbh_hid_keybd.c \
 #	usb_otg.c \
+	)
 
-SRC_CC3K = \
+SRC_CC3K = $(addprefix $(CC3KSRC)/,\
 	cc3000_common.c \
 	evnt_handler.c \
 	hci.c \
@@ -137,11 +131,12 @@ SRC_CC3K = \
 	wlan.c \
 	ccspi.c \
 	pybcc3k.c \
+	)
 
 OBJ = $(PY_O) $(addprefix $(BUILD)/, $(SRC_C:.c=.o) $(SRC_S:.s=.o) $(SRC_FATFS:.c=.o) $(SRC_STM:.c=.o)) # $(SRC_CC3K:.c=.o))
 #OBJ += $(addprefix $(BUILD)/, $(SRC_STM_OTG:.c=.o))
 
-all2: $(BUILD) $(BUILD)/flash.dfu
+all: $(BUILD) $(BUILD)/flash.dfu
 
 $(BUILD)/flash.dfu: $(BUILD)/flash0.bin $(BUILD)/flash1.bin
 	$(ECHO) "Create $@"
@@ -158,31 +153,5 @@ $(BUILD)/flash.elf: $(OBJ)
 	$(Q)$(LD) $(LDFLAGS) -o $@ $(OBJ) $(LIBS)
 	$(Q)$(SIZE) $@
 
-$(BUILD)/%.o: %.s
-	$(ECHO) "AS $<"
-	$(Q)$(AS) -o $@ $<
-
-$(BUILD)/%.o: %.c $(QSTR_DEFS)
-	$(ECHO) "CC $<"
-	$(Q)$(CC) $(CFLAGS) -c -o $@ $<
-
-$(BUILD)/%.o: $(FATFSSRC)/%.c
-	$(ECHO) "CC $<"
-	$(Q)$(CC) $(CFLAGS) -c -o $@ $<
-
-$(BUILD)/%.o: $(STMSRC)/%.c
-	$(ECHO) "CC $<"
-	$(Q)$(CC) $(CFLAGS) -c -o $@ $<
-
-#$(BUILD)/%.o: $(STMOTGSRC)/%.c
-#	$(ECHO) "CC $<"
-#	$(Q)$(CC) $(CFLAGS) -c -o $@ $<
-
-$(BUILD)/%.o: $(CC3KSRC)/%.c
-	$(ECHO) "CC $<"
-	$(Q)$(CC) $(CFLAGS) -c -o $@ $<
-
-clean:
-	$(RM) -rf $(BUILD)
+include ../py/mkrules.mk
 
-.PHONY: all all2 clean
diff --git a/teensy/Makefile b/teensy/Makefile
index e25f81481f..0cd7272e71 100644
--- a/teensy/Makefile
+++ b/teensy/Makefile
@@ -1,30 +1,20 @@
-# define main target
-all: all2
+include ../py/mkenv.mk
 
 # include py core make definitions
 include ../py/py.mk
 
-# program for deletion
-RM = /bin/rm
-ECHO = @echo
-
 ifeq ($(ARDUINO),)
 $(error Please define ARDUINO (where TeensyDuino is installed))
 endif
 TOOLS_PATH = $(ARDUINO)/hardware/tools
 COMPILER_PATH = $(TOOLS_PATH)/arm-none-eabi/bin
 CORE_PATH = $(ARDUINO)/hardware/teensy/cores/teensy3
-TARGET=TEENSY
 
-AS = $(COMPILER_PATH)/arm-none-eabi-as
-CC = $(COMPILER_PATH)/arm-none-eabi-gcc
-LD = $(COMPILER_PATH)/arm-none-eabi-ld
-OBJCOPY = $(COMPILER_PATH)/arm-none-eabi-objcopy
-SIZE = $(COMPILER_PATH)/arm-none-eabi-size
+CROSS_COMPILE = $(COMPILER_PATH)/arm-none-eabi-
 
 CFLAGS_TEENSY = -DF_CPU=96000000 -DUSB_SERIAL -D__MK20DX256__
 CFLAGS_CORTEX_M4 = -mthumb -mtune=cortex-m4 -mcpu=cortex-m4 -fsingle-precision-constant -Wdouble-promotion $(CFLAGS_TEENSY)
-CFLAGS = -I. -I$(PY_SRC) -I$(CORE_PATH) -Wall -ansi -std=gnu99
+CFLAGS = -I. -I$(PY_SRC) -I$(CORE_PATH) -Wall -ansi -std=gnu99 $(CFLAGS_CORTEX_M4)
 LDFLAGS = -nostdlib -T mk20dx256.ld
 LIBS = -L $(COMPILER_PATH)/../lib/gcc/arm-none-eabi/4.7.2/thumb2 -lgcc
 
@@ -35,9 +25,6 @@ else
 CFLAGS += -Os #-DNDEBUG
 endif
 
-# if order is not important for these, move them up
-CFLAGS += $(CFLAGS_CORTEX_M4) -D$(TARGET)
-
 SRC_C = \
 	main.c \
 	lcd.c \
@@ -47,13 +34,15 @@ SRC_C = \
 	memzip.c \
 	usb.c \
 
-STM_SRC_C = \
+STM_SRC_C = $(addprefix stm/,\
 	malloc0.c \
 	printf.c \
 	string0.c \
+	)
 
-STM_SRC_S = \
+STM_SRC_S = $(addprefix stm/,\
 	gchelper.s \
+	)
 
 SRC_TEENSY = \
 	mk20dx128.c \
@@ -70,7 +59,7 @@ OBJ = $(addprefix $(BUILD)/, $(SRC_C:.c=.o) $(STM_SRC_C:.c=.o) $(STM_SRC_S:.s=.o
 # the following is needed for BSD
 #LIB += -ltermcap
 
-all2: $(BUILD) hex
+all: hex
 hex: $(BUILD)/micropython-mz.hex
 
 post_compile: $(BUILD)/micropython-mz.hex
@@ -100,25 +89,7 @@ $(BUILD)/%.hex: $(BUILD)/%.elf
 	$(ECHO) "HEX $<"
 	$(Q)$(OBJCOPY) -O ihex -R .eeprom "$<" "$@"
 
-$(BUILD)/%.o: %.c
-	$(ECHO) "CC $<"
-	$(Q)$(CC) $(CFLAGS) -c -o $@ $<
-
-$(BUILD)/%.o: ../stm/%.s
-	$(ECHO) "AS $<"
-	$(Q)$(AS) -o $@ $<
-
-$(BUILD)/%.o: ../stm/%.c
-	$(ECHO) "CC $<"
-	$(Q)$(CC) $(CFLAGS) -c -o $@ $<
-
 $(BUILD)/%.o: $(CORE_PATH)/%.c
-	$(ECHO) "CC $<"
-	$(Q)$(CC) $(CFLAGS) -c -o $@ $<
-
-$(BUILD)/main.o: mpconfigport.h
-
-clean:
-	$(RM) -rf $(BUILD)
+	$(call compile_c)
 
-.PHONY: all all2 clean
+include ../py/mkrules.mk
diff --git a/unix-cpy/Makefile b/unix-cpy/Makefile
index f8ab73c354..84fc581e32 100644
--- a/unix-cpy/Makefile
+++ b/unix-cpy/Makefile
@@ -1,16 +1,12 @@
+include ../py/mkenv.mk
+
 # define main target
 PROG = cpy
-all: $(PROG)
 
 # include py core make definitions
 include ../py/py.mk
 
-# program for deletion
-RM = /bin/rm
-ECHO = @echo
-
 # compiler settings
-CC = gcc
 CFLAGS = -I. -I$(PY_SRC) -Wall -Werror -ansi -std=gnu99 -DUNIX
 LDFLAGS = -lm
 
@@ -28,20 +24,5 @@ SRC_C = \
 OBJ = $(PY_O) $(addprefix $(BUILD)/, $(SRC_C:.c=.o))
 LIB =
 
-$(PROG): $(BUILD) $(OBJ)
-	$(ECHO) "LINK $<"
-	$(Q)$(CC) -o $@ $(OBJ) $(LIB) $(LDFLAGS)
-	$(Q)strip $(PROG)
-	$(Q)size $(PROG)
-
-$(BUILD)/%.o: %.c
-	$(ECHO) "CC $<"
-	$(Q)$(CC) $(CFLAGS) -c -o $@ $<
-
-$(BUILD)/main.o: mpconfigport.h
-
-clean:
-	$(RM) -f $(PROG)
-	$(RM) -rf $(BUILD)
+include ../py/mkrules.mk
 
-.PHONY: all clean
diff --git a/unix/Makefile b/unix/Makefile
index 7a4ce3e161..3db6ae9dfd 100644
--- a/unix/Makefile
+++ b/unix/Makefile
@@ -1,6 +1,7 @@
+include ../py/mkenv.mk
+
 # define main target
 PROG = micropython
-all: $(PROG)
 
 # qstr definitions (must come before including py.mk)
 QSTR_DEFS = qstrdefsport.h
@@ -8,12 +9,7 @@ QSTR_DEFS = qstrdefsport.h
 # include py core make definitions
 include ../py/py.mk
 
-# program for deletion
-RM = /bin/rm
-ECHO = @echo
-
 # compiler settings
-CC = gcc
 CFLAGS = -I. -I$(PY_SRC) -Wall -Werror -ansi -std=gnu99 -DUNIX
 LDFLAGS = -lm
 
@@ -35,22 +31,5 @@ LIB = -lreadline
 # the following is needed for BSD
 #LIB += -ltermcap
 
-$(PROG): $(BUILD) $(OBJ)
-	$(ECHO) "LINK $<"
-	$(Q)$(CC) -o $@ $(OBJ) $(LIB) $(LDFLAGS)
-ifndef DEBUG
-	$(Q)strip $(PROG)
-endif
-	$(Q)size $(PROG)
-
-$(BUILD)/%.o: %.c $(QSTR_DEFS)
-	$(ECHO) "CC $<"
-	$(Q)$(CC) $(CFLAGS) -c -o $@ $<
-
-$(BUILD)/main.o: mpconfigport.h
-
-clean:
-	$(RM) -f $(PROG)
-	$(RM) -rf $(BUILD)
+include ../py/mkrules.mk
 
-.PHONY: all clean