Separate implementation from headers

Makefile

@@ -1,28 +1,47 @@
 TARGET := vitaminc
 CXX := g++
-CXXFLAGS = -g3 -std=c++14 -Wall
+CC = $(CXX)
+CXXFLAGS = -g3 -std=c++14 -Wall -MMD -Iinclude
+CFLAGS = $(CXXFLAGS)
 LEX = lex
 # C++ features are used, yacc doesn't suffice
 YACC = bison
 # -d: generate header with default name
 YFLAGS = --verbose --debug -d
 
+# Note that lex.yy.c is excluded deliberately, as "lex.yy.c" is considered a
+# header file (it's included by "y.tab.c").
+OBJS := $(shell find . -name "*.cpp") y.tab.o
+OBJS := $(OBJS:.cpp=.o)
+DEPS = $(OBJS:.o=.d)
+
 .PHONY: all clean test
 
 all: $(TARGET) test
 
 test: $(TARGET)
 	make -C test/
 
-$(TARGET): main.cpp lex.yy.c y.tab.c ast.hpp type.hpp scope.hpp symbol.hpp
-	$(CXX) $(CXXFLAGS) $< y.tab.c -o $@
+$(TARGET): $(OBJS)
+	$(CXX) $(CXXFLAGS) $(OBJS) -o $@
 
 lex.yy.c: lexer.l
-	$(LEX) -o $@ $^
+	$(LEX) -o $@ $<
+
+y.tab.h: y.tab.c
+y.tab.c: parser.y lex.yy.c
+	$(YACC) $(YFLAGS) $< -o $@
 
-y.tab.c: parser.y
-	$(YACC) $(YFLAGS) $^ -o $@
+#
+# Please note that although we're handling dependencies automatically with -MMD,
+# files that includes Flex or Bison-generated files still have to make such
+# dependency explicit to enforce the ordering.
+#
+
+main.o: %.o: %.cpp y.tab.h
 
 clean:
-	rm -rf *.s *.o lex.yy.c y.tab.c y.tab.h *.output *.ssa $(TARGET)
+	rm -rf *.s *.o lex.yy.c y.tab.c y.tab.h *.output *.ssa $(TARGET) $(OBJS) $(DEPS)
 	make -C test/ clean
+
+-include $(DEPS)