🔨 add dependency management

Author: csrohit

cpp/Makefile

@@ -48,13 +48,12 @@ INC_FLAGS 	= $(addprefix -I,$(INC_DIRS))
 # Target-specific flags
 CPU_FLAGS	?= -mfloat-abi=$(FLOAT_ABI) -m$(INSTR_SET) -mcpu=$(CPU)
 
-CPPFLAGS	?=$(DEFS) $(INC_FLAGS)
+CPPFLAGS	?= -MMD $(DEFS) $(INC_FLAGS)
 CFLAGS		?=$(CPU_FLAGS) $(OPT)
 CXXFLAGS 	:=$(CFLAGS) -fno-exceptions -fno-rtti
 LDFLAGS		?=$(CPU_FLAGS)
 
-# dependency
-CXXFLAGS += -M
+
 
 # Do not link stdlib with executable
 CFLAGS		+= -nostdlib -fno-tree-loop-distribute-patterns -fdata-sections -ffunction-sections
@@ -93,10 +92,10 @@ $(BUILD_DIR)/%.s:%.cpp
 	@echo "AS" $< " ==> " $@
 	$(CXX) $(CPPFLAGS) $(CXXLAGS) -o $@ -S $<
 
-# $(BUILD_DIR)/%.o:%.c
-# 	@mkdir -p $(dir $@)
-# 	@echo "CC" $< " ==> " $@
-# 	$(CC) $(CPPFLAGS) $(CFLAGS) -o $@ -c $<
+$(BUILD_DIR)/%.o:%.c
+	@mkdir -p $(dir $@)
+	@echo "CC" $< " ==> " $@
+	$(CC) $(CPPFLAGS) $(CFLAGS) -o $@ -c $<
 
 $(BUILD_DIR)/%.o:%.cpp
 	@mkdir -p $(dir $@)
@@ -105,7 +104,7 @@ $(BUILD_DIR)/%.o:%.cpp
 
 $(BUILD_DIR)/$(TARGET).elf: $(OBJS)
 	@echo "Linking sources into "$@
-	@$(CC) $(LDFLAGS) -o $@ $^
+	$(CC) $(LDFLAGS) -o $@ $^
 
 
 flash: bin
@@ -117,3 +116,6 @@ debug: all
 
 clean:
 	rm -rf build
+
+
+-include $(OBJS:%.o=%.d)

cpp/README.md

@@ -135,3 +135,22 @@ make flash
 3. Click in Run and Debug option in VsCode sidebar. Then launch Cortex Debug target.
 
 Happy debugging....
+
+### Dependency option
+-M
+    Outputs a rule suitable for makefile, does not compile the file
+    The generated rule does not have a command
+
+-MM
+    Outputs a rule suitable for makefile, does not compile the file.
+    In the dependencies only include user files, do not include system header files
+
+-MT/-MQ (-MM -MT abc.o) => change the target
+    This changes the name of the target
+-MT => generates the same string as provided
+-MQ => replaces value of the make variable in the target (expansation)
+
+-MD => D represents that the preprocessor output should be generated as a side effect and the main compilation happens
+    If -o options is specified then it is taken as name for the preprocessor output with .d
+    else name of input file is taken with extensions as .d
+    To override the name of the pre-processor output file -MF option should be used

cpp/main.s

@@ -0,0 +1,13 @@
+	.cpu arm7tdmi
+	.arch armv4t
+	.fpu softvfp
+	.eabi_attribute 20, 1
+	.eabi_attribute 21, 1
+	.eabi_attribute 23, 3
+	.eabi_attribute 24, 1
+	.eabi_attribute 25, 1
+	.eabi_attribute 26, 1
+	.eabi_attribute 30, 6
+	.eabi_attribute 34, 0
+	.eabi_attribute 18, 4
+	.file	"main.cpp"