Q6: A better makefile and code organization

Q6-cache/Makefile

@@ -1,32 +1,120 @@
-SHELL := /bin/bash
+#
+# Makefile
+#
+# Copyright (C) 2020 Christos Choutouridis <cchoutou@ece.auth.gr>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as
+# published by the Free Software Foundation, either version 3
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
 
-######################################################################
-### EXECUTABLES
+# ========== Project settings ==========
+TARGET      := matmul
+SRC_DIR     := src
+INC_DIR     := 
+EXC_FILE    := 
 
-CC    = gcc
-FLAGS = -O3 -Wall -std=gnu99
-RM    = rm -rf
-LINK  = -lm
+# build directories
+BUILD_DIR   := bin
+OBJ_DIR     := $(BUILD_DIR)/obj
+DEP_DIR     := $(BUILD_DIR)/.dep
 
-######################################################################
-### TARGET FILES
+# ========== Compiler settings ==========
+CXX         := gcc
+CPP         := gcc -E
+CSIZE       := size
 
-MAIN = matmul
+CFLAGS      := -std=gnu99 -Wall -Wextra
+DEB_FLAGS   := -DDEBUG -g3
+REL_FLAGS   := -O3
+LDFLAGS     := -lm
 
-######################################################################
-### CLEAN-UP FILES
+PRE_DEFS    := 
 
-FILES_CLEAN = $(MAIN) *~
+#
+# =========== Main body and Patterns ===========
+#
+INC         := $(foreach dir,$(INC_DIR),-I$(dir))
+DEF         := $(foreach def,$(PRE_DEFS),-D$(def))
 
-######################################################################
-### COMMANDS -- ! DO NOT CHANGE BELOW !
+# source files
+# recursive search into current and source directories
+SRC         := $(wildcard *.c)
+SRC         += $(foreach dir,$(SRC_DIR),$(wildcard $(dir)/*.c))
+SRC         += $(foreach dir,$(SRC_DIR),$(wildcard $(dir)/**/*.c))
+# exclude every file from the exclude file list
+SRC         := $(filter-out $(wildcard $(EXC_FILE)),$(SRC))
 
-all: $(MAIN)
+OBJ         := $(foreach file,$(SRC:%.c=%.o),$(OBJ_DIR)/$(file))
+DEP         := $(foreach file,$(SRC:%.c=%.d),$(DEP_DIR)/$(file))
 
-$(MAIN): $(MAIN).c
-	$(CC) $(FLAGS) $(DEFS) $^ -o $@ $(LINK)
 
+# Make Dependencies pattern.
+# This little trick enables recompilation only when dependencies change
+# and it does so for changes both in source AND header files ;)
+# 
+# It is based on Tom Tromey's method.
+# 
+# Invoke cpp to create makefile rules with dependencies for each source file
+$(DEP_DIR)/%.d: %.c
+	@mkdir -p $(@D)
+	@$(CPP) $(CFLAGS) $(INC) $(DEF) -MM -MT $(OBJ_DIR)/$(<:.c=.o) -MF $@ $<
+
+
+# objects depent on .c AND dependency files, which have an empty recipe 
+$(OBJ_DIR)/%.o: %.c $(DEP_DIR)/%.d
+	@mkdir -p $(@D)
+	$(CXX) -c $(CFLAGS) $(INC) $(DEF) -o $@ $<
+
+# empty recipe for dependency files. This prevents make errors
+$(DEP):
+
+# now include all dependencies
+# After all they are makefile dependency rules ;)
+include $(wildcard $(DEP))
+
+# main target rule
+$(BUILD_DIR)/$(TARGET): $(OBJ)
+	@mkdir -p $(@D)
+	@echo Linking to target: $(TARGET)
+	@echo $(CXX) $(LDFLAGS) -o $(@D)/$(TARGET) '$$(OBJ)'
+	@$(CXX) $(LDFLAGS) -o $(@D)/$(TARGET) $(OBJ)
+	@echo
+	@echo Print size information
+	@$(CSIZE) $(@D)/$(TARGET)
+	@echo Done
+
+
+.PHONY: clean
 clean:
-	$(RM) $(FILES_CLEAN) *.o *~
+	@echo Cleaning build directories
+	@rm -rf $(OBJ_DIR)
+	@rm -rf $(DEP_DIR)
+	@rm -rf $(BUILD_DIR)
+
+#
+# ============ User Rules =============
+#
+
+.PHONY: debug
+debug: CFLAGS += $(DEB_FLAGS)
+debug: $(BUILD_DIR)/$(TARGET)
+
+
+.PHONY: release
+release: CFLAGS += $(REL_FLAGS)
+release: clean $(BUILD_DIR)/$(TARGET)
+
+
+.PHONY: all
+all: clean release
 
-.PHONY: $(MAIN)