Fix/improve depdendency handling. Deps are autogenerated on the first compile pass and consumed on subsequent builds. This helps work around the difficulty of building the 'clean' target with Eclipse.

libraries/AP_Common/Arduino.mk

@@ -146,15 +146,16 @@ endif
 #
 DEFINES			=	-DF_CPU=$(F_CPU) -DARDUINO=$(ARDUINO_VERS)
 OPTFLAGS		=	-Os
+DEPFLAGS		=	-MD -MT $@
 
 # XXX warning options TBD
 CXXOPTS			= 	-mcall-prologues -ffunction-sections -fdata-sections -fno-exceptions
 COPTS			=	-mcall-prologues -ffunction-sections -fdata-sections
 ASOPTS			=	-assembler-with-cpp 
 
-CXXFLAGS		=	-g -mmcu=$(MCU) $(DEFINES) $(OPTFLAGS) $(CXXOPTS)
-CFLAGS			=	-g -mmcu=$(MCU) $(DEFINES) $(OPTFLAGS) $(COPTS)
-ASFLAGS			=	-g -mmcu=$(MCU) $(DEFINES) $(ASOPTS)
+CXXFLAGS		=	-g -mmcu=$(MCU) $(DEFINES) $(OPTFLAGS) $(DEPFLAGS) $(CXXOPTS)
+CFLAGS			=	-g -mmcu=$(MCU) $(DEFINES) $(OPTFLAGS) $(DEPFLAGS) $(COPTS)
+ASFLAGS			=	-g -mmcu=$(MCU) $(DEFINES) $(DEPFLAGS) $(ASOPTS)
 LDFLAGS			=	-g -mmcu=$(MCU) $(OPTFLAGS) -Wl,--gc-sections
 
 LIBS			=	-lm
@@ -291,6 +292,12 @@ SKETCHEEP		=	$(BUILDROOT)/$(SKETCH).eep
 # The core library
 CORELIB			=	$(BUILDROOT)/$(HARDWARE)/core.a
 
+# All of the objects that may be built
+ALLOBJS			=	$(SKETCHOBJS) $(LIBOBJS) $(CORELIBOBJS)
+
+# All of the dependency files that may be generated
+ALLDEPS			=	$(ALLOBJS:%.o=%.d)
+
 ################################################################################
 # Targets
 #
@@ -306,6 +313,9 @@ clean:
 # Rules
 #
 
+# fetch dependency info from a previous build if any of it exists
+-include $(ALLDEPS)
+
 # common header for rules, prints what is being built
 define RULEHDR
 	@echo %% $(subst $(BUILDROOT)/,,$@)
@@ -327,10 +337,6 @@ $(SKETCHEEP):	$(SKETCHELF)
 	$(RULEHDR)
 	$(v)$(OBJCOPY) -O ihex -j.eeprom --set-section-flags=.eeprom=alloc,load --no-change-warnings --change-section-lma .eeprom=0 $< $@
 
-# Make the buildroot
-$(BUILDROOT):
-	@mkdir -p $(BUILDROOT)
-
 #
 # Build sketch objects
 #
@@ -425,7 +431,7 @@ $(CORELIB): $(CORELIBOBJS)
 # In addition, we add #line directives wherever the originating file changes
 # to help backtrack from compiler messages and in the debugger.
 #
-$(SKETCHCPP):	$(SKETCHCPP_SRC) $(BUILDROOT)
+$(SKETCHCPP):	$(SKETCHCPP_SRC)
 	$(RULEHDR)
 	$(v)$(AWK) -v mode=header '$(SKETCH_SPLITTER)'   $(SKETCHCPP_SRC) >  $@
 	$(v)echo "#line 1 \"autogenerated\""                              >> $@