Refine build system for efficient configurations

This addresses build system inefficiencies and compatibility issues:
1. Configuration change detection: Use cmp-based comparison to avoid
   unnecessary rebuilds when configuration hasn't actually changed.
   Previously, every make run would touch .config and trigger full
   rebuilds.
2. Directory creation optimization: Replace runtime mkdir -p $(shell dirname)
   calls with order-only prerequisites (|).
3. Configuration dependency tracking: Add $(CONFIG_FILE) as explicit
   prerequisite to all compilation rules. This ensures object files
   rebuild when feature flags change (e.g., ENABLE_JIT=1 -> 0).
4. Build system hygiene: Remove duplicate .PHONY declarations, fix shell
   script indentation in riscv-arch-test.mk, and add .PHONY coverage for
   all target declarations.

Author: jserv

Makefile

@@ -1,6 +1,11 @@
 include mk/common.mk
 include mk/toolchain.mk
 
+# Verify GNU make version (3.80+ required for order-only prerequisites)
+ifeq ($(filter 3.80 3.81 3.82 3.83 3.84 4.% 5.%,$(MAKE_VERSION)),)
+$(error GNU make 3.80 or higher is required. Current version: $(MAKE_VERSION))
+endif
+
 OUT ?= build
 BIN := $(OUT)/rv32emu
 
@@ -46,6 +51,7 @@ endif
 #   Device Tree(initrd, memory range)
 #   src/io.c(memory init)
 #   src/riscv.c(system emulation layout init)
+# Note: These memory settings are for SYSTEM mode only (when ELF_LOADER=0)
 ifeq ($(call has, SYSTEM), 1)
 ifeq ($(call has, ELF_LOADER), 0)
 MiB = 1024*1024
@@ -66,6 +72,7 @@ CFLAGS_dt += -DMEM_START=0x$(MEM_START) \
              -DINITRD_END=0x$(shell echo "obase=16; ibase=16; \
                             $(REAL_MEM_SIZE) - $(call compute_size, $(DTB_SIZE)) - 1" | bc)
 
+# Memory size for SYSTEM mode (may be overridden by FULL4G if ENABLE_ELF_LOADER=1)
 CFLAGS += -DMEM_SIZE=0x$(REAL_MEM_SIZE) -DDTB_SIZE=0x$(REAL_DTB_SIZE) -DINITRD_SIZE=0x$(REAL_INITRD_SIZE)
 endif
 endif
@@ -206,7 +213,22 @@ endif
 # Full access to a 4 GiB address space, necessitating more memory mapping
 # during emulator initialization.
 $(call set-feature, FULL4G)
+
+# Configuration validation and conflict detection
+ifeq ($(call has, SDL), 1)
+ifeq ($(call has, SYSTEM), 1)
+ifeq ($(call has, ELF_LOADER), 0)
+ifeq ($(call has, FULL4G), 0)
+    $(warning SDL requires FULL4G=1 but SYSTEM forces FULL4G=0. Set ENABLE_ELF_LOADER=1 or disable SDL/SYSTEM)
+endif
+endif
+endif
+endif
+
 ifeq ($(call has, FULL4G), 1)
+# Note: If both SYSTEM and FULL4G are enabled with ELF_LOADER=1,
+# this MEM_SIZE definition will override the SYSTEM mode definition.
+# This is intentional for ELF loader use cases.
 CFLAGS += -DMEM_SIZE=0xFFFFFFFFULL # 2^{32} - 1
 endif
 
@@ -259,6 +281,8 @@ ifeq ($(call has, JIT), 1)
         else
             $(error No llvm-config-18 installed. Check llvm-config-18 installation in advance, or use "ENABLE_T2C=0" to disable tier-2 LLVM compiler)
         endif
+    else
+        $(warning T2C (tier-2 compiler) is disabled. Using tier-1 JIT only.)
     endif
     ifneq ($(processor),$(filter $(processor),x86_64 aarch64 arm64))
         $(error JIT mode only supports for x64 and arm64 target currently.)
@@ -292,7 +316,7 @@ include mk/artifact.mk
 include mk/system.mk
 include mk/wasm.mk
 
-all: config $(BUILD_DTB) $(BUILD_DTB2C) $(BIN)
+all: $(BUILD_DTB) $(BUILD_DTB2C) $(BIN)
 
 OBJS := \
     map.o \
@@ -327,19 +351,30 @@ ifeq ($(call has, GDBSTUB), 1)
 $(OBJS): $(GDBSTUB_LIB)
 endif
 
-$(OUT)/%.o: src/%.c $(deps_emcc)
-	$(Q)mkdir -p $(shell dirname $@)
+$(OUT)/%.o: src/%.c $(CONFIG_FILE) $(deps_emcc) | $(OUT)
 	$(VECHO) "  CC\t$@\n"
 	$(Q)$(CC) -o $@ $(CFLAGS) $(CFLAGS_emcc) -c -MMD -MF $@.d $<
 
-$(BIN): $(OBJS) $(DEV_OBJS)
+$(OUT):
+	$(Q)mkdir -p $@
+
+$(BIN): $(OBJS) $(DEV_OBJS) | $(OUT)
 	$(VECHO) "  LD\t$@\n"
 	$(Q)$(CC) -o $@ $(CFLAGS_emcc) $^ $(LDFLAGS)
 
+$(CONFIG_FILE): FORCE
+	$(Q)mkdir -p $(OUT)
+	$(Q)echo "$(CFLAGS)" | xargs -n1 | sort | sed -n 's/^RV32_FEATURE/ENABLE/p' > $@.tmp
+	$(Q)if ! cmp -s $@ $@.tmp 2>/dev/null; then \
+		mv $@.tmp $@; \
+		$(PRINTF) "Configuration updated. Check $(OUT)/.config for configured items.\n"; \
+	else \
+		$(RM) $@.tmp; \
+	fi
+
+.PHONY: FORCE config
+FORCE:
 config: $(CONFIG_FILE)
-$(CONFIG_FILE):
-	$(Q)echo "$(CFLAGS)" | xargs -n1 | sort | sed -n 's/^RV32_FEATURE/ENABLE/p' > $@
-	$(VECHO) "Check the file $(OUT)/.config for configured items.\n"
 
 # Tools
 include mk/tools.mk
@@ -434,4 +469,7 @@ distclean: clean
 	$(Q)-$(RM) -r $(SOFTFLOAT_DUMMY_PLAT) $(OUT)/softfloat
 	$(Q)$(call notice, [OK])
 
+.PHONY: all config tool check check-hello misalign misalign-in-blk-emu mmu-test
+.PHONY: gdbstub-test doom quake clean distclean artifact
+
 -include $(deps)

mk/artifact.mk

@@ -41,7 +41,7 @@ SHELL_HACK := $(shell mkdir -p $(BIN_DIR)/linux-x86-softfp $(BIN_DIR)/riscv32 $(
 # $(3): name showing in terminal
 define fetch-releases-tag
     $(if $(wildcard $(BIN_DIR)/$(2)), \
-        $(info $(call warnx, $(3) is found. Skipping downloading.)), \
+        $(warning $(3) is found. Skipping downloading.), \
         $(eval LATEST_RELEASE := $(shell wget -q https://api.github.com/repos/sysprog21/rv32emu-prebuilt/releases -O- \
                                          | grep '"tag_name"' \
                                          | grep "$(1)" \

mk/external.mk

@@ -4,20 +4,19 @@ COMPRESSED_IS_DIR :=
 EXTRACTOR :=
 VERIFIER :=
 
-# temporarily files to store correct SHA value and computed SHA value
+# Temporary files to store correct SHA value and computed SHA value
 # respectively for verification of directory source
-$(eval SHA_FILE1 := $(shell mktemp))
-$(eval SHA_FILE2 := $(shell mktemp))
+SHA_FILE1 := $(shell mktemp)
+SHA_FILE2 := $(shell mktemp)
 
 # $(1): compressed source
 define prologue
-    $(eval _ := $(shell echo "  GET\t$(1)\n"))
-    $(info $(_))
+    $(warning GET	$(1))
 endef
 
 # $(1), $(2), $(3): files to be deleted
 define epilogue
-    $(eval _ := $(shell $(RM) $(1) $(2) $(3)))
+    $(RM) $(1) $(2) $(3)
 endef
 
 # $(1): compressed source URL

mk/riscv-arch-test.mk

@@ -1,8 +1,8 @@
 riscof-check:
 	$(Q)if [ "$(shell pip show riscof 2>&1 | head -n 1 | cut -d' ' -f1)" = "WARNING:" ]; then \
-	$(PRINTF) "Run 'pip3 install -r requirements.txt to install dependencies.\n"; \
-	exit 1; \
-	fi;
+		$(PRINTF) "Run 'pip3 install -r requirements.txt' to install dependencies.\n"; \
+		exit 1; \
+	fi
 
 ARCH_TEST_DIR ?= tests/riscv-arch-test
 ARCH_TEST_SUITE ?= $(ARCH_TEST_DIR)/riscv-test-suite
@@ -27,3 +27,5 @@ endif
 			--config=$(RISCV_TARGET)/config.ini \
 			--suite=$(ARCH_TEST_SUITE) \
 			--env=$(ARCH_TEST_DIR)/riscv-test-suite/env
+
+.PHONY: riscof-check arch-test

mk/softfloat.mk

@@ -334,11 +334,13 @@ $(SOFTFLOAT_DUMMY_PLAT):
 	$(Q)touch $@
 
 $(SOFTFLOAT_FILES): $(SOFTFLOAT_SENTINEL)
-$(OUT)/softfloat/%.o: $(SOFTFLOAT_DIR)/%.c $(SOFTFLOAT_SENTINEL) $(SOFTFLOAT_DUMMY_PLAT)
-	$(Q)mkdir -p $(shell dirname $@)
+$(OUT)/softfloat/%.o: $(SOFTFLOAT_DIR)/%.c $(CONFIG_FILE) $(SOFTFLOAT_SENTINEL) $(SOFTFLOAT_DUMMY_PLAT) | $(OUT)/softfloat $(OUT)/softfloat/RISCV
 	$(VECHO) "  CC\t$@\n"
 	$(Q)$(CC) -o $@ $(CFLAGS) $(CFLAGS_softfloat) -c -MMD -MF $@.d $<
 
+$(OUT)/softfloat $(OUT)/softfloat/RISCV:
+	$(Q)mkdir -p $@
+
 SOFTFLOAT_LIB := $(OUT)/softfloat/softfloat.a
 $(SOFTFLOAT_LIB): $(SOFTFLOAT_OBJS)
 	$(VECHO) "  AR\t$@\n"

mk/system.mk

@@ -29,10 +29,13 @@ $(BUILD_DTB2C): $(BIN_TO_C) $(BUILD_DTB)
 	$(VECHO) "  BIN2C\t$@\n"
 	$(Q)$(BIN_TO_C) $(BUILD_DTB) > $@
 
-$(DEV_OUT)/%.o: $(DEV_SRC)/%.c $(deps_emcc)
-	$(Q)mkdir -p $(DEV_OUT)
+$(DEV_OUT)/%.o: $(DEV_SRC)/%.c $(CONFIG_FILE) $(deps_emcc) | $(DEV_OUT)
 	$(VECHO) "  CC\t$@\n"
 	$(Q)$(CC) -o $@ $(CFLAGS) $(CFLAGS_emcc) -c -MMD -MF $@.d $<
+
+$(DEV_OUT):
+	$(Q)mkdir -p $@
+
 DEV_OBJS := $(patsubst $(DEV_SRC)/%.c, $(DEV_OUT)/%.o, $(wildcard $(DEV_SRC)/*.c))
 deps := $(DEV_OBJS:%.o=%.o.d)
 
@@ -46,4 +49,6 @@ system_deps += artifact $(BUILD_DTB) $(BUILD_DTB2C) $(BIN)
 system: $(system_deps)
 	$(system_action)
 
+.PHONY: system
+
 endif

mk/tests.mk

@@ -85,31 +85,39 @@ $(CACHE_TEST_TARGET): $(CACHE_TEST_OBJS)
 	$(VECHO) "  CC\t$@\n"
 	$(Q)$(CC) $^ -o $@ $(LDFLAGS)
 
-$(CACHE_TEST_OUTDIR)/%.o: $(CACHE_TEST_SRCDIR)/%.c
+$(CACHE_TEST_OUTDIR)/%.o: $(CACHE_TEST_SRCDIR)/%.c $(CONFIG_FILE) | $(CACHE_TEST_OUTDIR) $(CACHE_TEST_OUTDIR)/lfu
 	$(VECHO) "  CC\t$@\n"
-	$(Q)mkdir -p $(dir $@)/lfu
 	$(Q)$(CC) -o $@ $(CFLAGS) -I./src -c -MMD -MF $@.d $<
 
+$(CACHE_TEST_OUTDIR) $(CACHE_TEST_OUTDIR)/lfu:
+	$(Q)mkdir -p $@
+
 $(MAP_TEST_OUT): $(MAP_TEST_TARGET)
 	$(Q)touch $@
 
 $(MAP_TEST_TARGET): $(MAP_TEST_OBJS)
 	$(VECHO) "  CC\t$@\n"
 	$(Q)$(CC) $^ -o $@ $(LDFLAGS)
 
-$(MAP_TEST_OUTDIR)/%.o: $(MAP_TEST_SRCDIR)/%.c
+$(MAP_TEST_OUTDIR)/%.o: $(MAP_TEST_SRCDIR)/%.c $(CONFIG_FILE) | $(MAP_TEST_OUTDIR)
 	$(VECHO) "  CC\t$@\n"
-	$(Q)mkdir -p $(dir $@)
 	$(Q)$(CC) -o $@ $(CFLAGS) -I./src -c -MMD -MF $@.d $<
 
+$(MAP_TEST_OUTDIR):
+	$(Q)mkdir -p $@
+
 $(PATH_TEST_OUT): $(PATH_TEST_TARGET)
 	$(Q)touch $@
 
 $(PATH_TEST_TARGET): $(PATH_TEST_OBJS)
 	$(VECHO) "  CC\t$@\n"
 	$(Q)$(CC) $^ -o $@ $(LDFLAGS)
 
-$(PATH_TEST_OUTDIR)/%.o: $(PATH_TEST_SRCDIR)/%.c
+$(PATH_TEST_OUTDIR)/%.o: $(PATH_TEST_SRCDIR)/%.c $(CONFIG_FILE) | $(PATH_TEST_OUTDIR)
 	$(VECHO) "  CC\t$@\n"
-	$(Q)mkdir -p $(dir $@)
 	$(Q)$(CC) -o $@ $(CFLAGS) -I./src -c -MMD -MF $@.d $<
+
+$(PATH_TEST_OUTDIR):
+	$(Q)mkdir -p $@
+
+.PHONY: tests run-test-cache run-test-map run-test-path

mk/tools.mk

@@ -23,7 +23,7 @@ HIST_OBJS := \
 HIST_OBJS := $(addprefix $(OUT)/, $(HIST_OBJS))
 deps += $(HIST_OBJS:%.o=%.o.d)
 
-$(OUT)/%.o: tools/%.c
+$(OUT)/%.o: tools/%.c | $(OUT)
 	$(VECHO) "  CC\t$@\n"
 	$(Q)$(CC) -o $@ $(CFLAGS) -Wno-missing-field-initializers -Isrc -c -MMD -MF $@.d $<
 
@@ -39,3 +39,5 @@ LINUX_IMAGE_SRC = $(BUILDROOT_DATA) $(LINUX_DATA)
 build-linux-image: $(LINUX_IMAGE_SRC)
 	$(Q)./tools/build-linux-image.sh
 	$(Q)$(PRINTF) "Build done.\n"
+
+.PHONY: build-linux-image

mk/wasm.mk

@@ -99,14 +99,14 @@ FIREFOX_MAJOR := $(shell $(FIREFOX_MAJOR_VERSION_CHECK_CMD))
 
 # Chrome
 ifeq ($(shell echo $(CHROME_MAJOR)\>=$(CHROME_SUPPORT_TCO_AT_MAJOR) | bc), 1)
-    $(info $(call noticex, $(CHROME_SUPPORT_TCO_INFO)))
+    $(warning $(CHROME_SUPPORT_TCO_INFO))
 else
     $(warning $(call warnx, $(CHROME_NO_SUPPORT_TCO_WARNING)))
 endif
 
 # Firefox
 ifeq ($(shell echo $(FIREFOX_MAJOR)\>=$(FIREFOX_SUPPORT_TCO_AT_MAJOR) | bc), 1)
-    $(info $(call noticex, $(FIREFOX_SUPPORT_TCO_INFO)))
+    $(warning $(FIREFOX_SUPPORT_TCO_INFO))
 else
     $(warning $(call warnx, $(FIREFOX_NO_SUPPORT_TCO_WARNING)))
 endif
@@ -118,7 +118,7 @@ SAFARI_VERSION := $(shell $(SAFARI_VERSION_CHECK_CMD))
 SAFARI_MAJOR := $(shell echo $(SAFARI_VERSION) | cut -f1 -d.)
 SAFARI_MINOR := $(shell echo $(SAFARI_VERSION) | cut -f2 -d.)
 ifeq ($(shell echo "$(SAFARI_MAJOR).$(SAFARI_MINOR)>=$(SAFARI_SUPPORT_TCO_AT_MAJOR_MINOR)" | bc), 1)
-    $(info $(call noticex, $(SAFARI_SUPPORT_TCO_INFO)))
+    $(warning $(SAFARI_SUPPORT_TCO_INFO))
 else
     $(warning $(call warnx, $(SAFARI_NO_SUPPORT_TCO_WARNING)))
 endif
@@ -134,10 +134,10 @@ check-demo-dir-exist:
 		mkdir -p "$(DEMO_DIR)"; \
 	fi
 
-# FIXME: without $(info) generates errors
+# FIXME: empty statement needed to avoid macro expansion errors
 define cp-web-file
     $(Q)cp $(1) $(DEMO_DIR)
-    $(info)
+    @:
 endef
 
 # WEB_FILES could be cleaned and recompiled, thus do not mix these two files into WEB_FILES
@@ -159,4 +159,7 @@ start-web: $(start_web_deps)
 	$(foreach T, $(STATIC_WEB_FILES), $(call cp-web-file, $(T)))
 	$(Q)mv $(DEMO_DIR)/*.html $(DEMO_DIR)/index.html
 	$(Q)python3 -m http.server --bind $(DEMO_IP) $(DEMO_PORT) --directory $(DEMO_DIR)
+
+.PHONY: check-demo-dir-exist start-web
+
 endif