build: track header dependencies and report the RCM size limit

Makefile

@@ -44,11 +44,13 @@ CUSTOMDEFINES += -DGFX_INC=$(GFX_INC) -DFFCFG_INC=$(FFCFG_INC)
 CUSTOMDEFINES += -DVERSION='"$(VERSION)"'
 
 ARCH := -march=armv4t -mtune=arm7tdmi -mthumb -mthumb-interwork
-CFLAGS = $(ARCH) -Os -nostdlib -ffunction-sections -fdata-sections -fomit-frame-pointer -fno-inline -std=gnu11 -Wall -Wno-missing-braces $(CUSTOMDEFINES)
+CFLAGS = $(ARCH) -Os -nostdlib -ffunction-sections -fdata-sections -fomit-frame-pointer -fno-inline -std=gnu11 -Wall -Wno-missing-braces -MMD -MP $(CUSTOMDEFINES)
 LDFLAGS = $(ARCH) -nostartfiles -lgcc -Wl,--nmagic,--gc-sections -Xlinker --defsym=IPL_LOAD_ADDR=$(IPL_LOAD_ADDR)
 
 ################################################################################
 
+MAX_PAYLOAD_SIZE := 126296
+
 RAMTEST_BIN := $(OUTPUTDIR)/RAM-Test.bin
 OBJS_RAMTEST := $(filter-out $(BUILDDIR)/$(TARGET)/main.o,$(OBJS)) \
 	$(BUILDDIR)/$(TARGET)/ram_test_main.o
@@ -57,8 +59,8 @@ OBJS_RAMTEST := $(filter-out $(BUILDDIR)/$(TARGET)/main.o,$(OBJS)) \
 
 all: $(OUTPUTDIR)/$(OUTPUT_NAME)
 	$(eval BIN_SIZE = $(shell wc -c < $(OUTPUTDIR)/$(OUTPUT_NAME)))
-	@echo "Payload size is $(BIN_SIZE) bytes"
-	@echo "Max size is 126296 bytes."
+	@echo "Payload size is $(BIN_SIZE) bytes (max $(MAX_PAYLOAD_SIZE) for RCM)"
+	@if [ $(BIN_SIZE) -gt $(MAX_PAYLOAD_SIZE) ]; then echo "WARNING: payload exceeds the RCM size limit"; fi
 
 clean:
 	@rm -rf $(BUILDDIR)
@@ -105,6 +107,9 @@ $(BUILDDIR)/$(TARGET)/%.o: $(BDKDIR)/%.S
 	@mkdir -p "$(@D)"
 	$(CC) $(CFLAGS) -c $< -o $@
 
+# Header dependencies (generated by -MMD)
+-include $(OBJS:.o=.d) $(BUILDDIR)/$(TARGET)/ram_test_main.d
+
 release: $(OUTPUTDIR)/$(OUTPUT_NAME)
 	@mkdir -p release/bootloader/payloads
 	@cp $(OUTPUTDIR)/$(OUTPUT_NAME) release/bootloader/payloads/$(OUTPUT_NAME)