Update Makefile to produce dependencies & objects

Makefile

@@ -1,19 +1,48 @@
+# Executable
+TARGET := main.out
 
+# Paths to source, dependency, object files
+SPATH = src
+IPATH = inc
+DPATH = dep
+OPATH = obj
+
+VPATH = $(SPATH) $(OPATH) $(IPATH) $(DPATH)
+
+# compiler and compiler flags
 CC = g++
-CFLAGS = -Iinc -pthread -lrt
-VPATH = src
+CFLAGS = -MMD -I$(IPATH) -pthread -lrt
 
-OBJECTS := %.o list.o producer.o transformer.o consumer.o
-EXECUTE := main.out #test.out
+# list of object files
+SOURCES = $(wildcard $(SPATH)/*.cpp)
+OBJECTS = $(addprefix $(OPATH)/,$(notdir $(SOURCES:.cpp=.o)))
 
-.PHONY: all clean
+.PHONY: all clean dump
 
-all: $(EXECUTE)
+all: $(DPATH) $(OPATH) $(TARGET)
+
+dump:
+	@echo SOURCES: $(SOURCES)
+	@echo OBJECTS: $(OBJECTS)
+	@echo TARGET:  $(TARGET)
+	@echo VPATH:   $(VPATH)
 
 clean:
-	rm $(EXECUTE)
+	-rm $(TARGET)
+	-rm -r dep obj
 
+$(DPATH) $(OPATH):
+	mkdir -p $@
+
+# Make the executable(s)
 %.out: $(OBJECTS)
 	$(CC) $(CFLAGS) -o $@ $^
-%.o: %.cpp
-	$(CC) $(CFLAGS) -c $<
+# Make the object and dependency files
+$(OPATH)/%.o $(DPATH)/%.d: $(SPATH)/%.cpp
+	$(CC) $(CFLAGS) -MF $(DPATH)/$(@F:.o=.d) -o $@ -c $<
+
+# Don't delete object files:
+.PRECIOUS: $(OPATH)/%.o $(DPATH)/%.d
+
+# use dependencies when rebuilding
+-include $(addprefix $(DPATH)/,$(wildcard *.d))