Validate the prerequisites before building

To prevent users from building shecc without certain required packages,
these changes modify the build system to check for prerequisites
when building.

The build system now lists all necessary tools, verify the existence
of their executables, and prints warning messages if any required tool
is missing.

If qemu is required but missing, the build process will proceed only
up to stage 0, print warning messages and stop at the beginning of
stage 1.

Close #44

Author: DrXiao

Makefile

@@ -16,7 +16,6 @@ CFLAGS := -O -g \
 
 BUILD_SESSION := .session.mk
 
-include mk/common.mk
 -include $(BUILD_SESSION)
 
 STAGE0 := shecc
@@ -26,6 +25,7 @@ STAGE2 := shecc-stage2.elf
 OUT ?= out
 ARCHS = arm riscv
 ARCH ?= $(firstword $(ARCHS))
+HOST_ARCH = $(shell arch 2>/dev/null)
 SRCDIR := $(shell find src -type d)
 LIBDIR := $(shell find lib -type d)
 
@@ -42,12 +42,14 @@ ifeq (,$(filter $(ARCH),$(ARCHS)))
 $(error Support ARM and RISC-V only. Select the target with "ARCH=arm" or "ARCH=riscv")
 endif
 include mk/$(ARCH).mk
+include mk/common.mk
 
 config:
 	$(Q)ln -s $(PWD)/$(SRCDIR)/$(ARCH)-codegen.c $(SRCDIR)/codegen.c
-	$(call $(ARCH)-specific-defs) > $@
+	$(Q)$(PRINTF) $(ARCH_DEFS) > $@
 	$(VECHO) "Target machine code switch to %s\n" $(ARCH)
 	$(Q)$(MAKE) $(BUILD_SESSION) --silent
+	$(Q)$(CONFIG_CHECK_CMD)
 
 $(OUT)/tests/%.elf: tests/%.c $(OUT)/$(STAGE0)
 	$(VECHO) "  SHECC\t$@\n"
@@ -103,6 +105,7 @@ $(OUT)/$(STAGE0): $(OUT)/libc.inc $(OBJS)
 	$(Q)$(CC) $(OBJS) -o $@
 
 $(OUT)/$(STAGE1): $(OUT)/$(STAGE0)
+	$(Q)$(STAGE1_CHECK_CMD)
 	$(VECHO) "  SHECC\t$@\n"
 	$(Q)$(OUT)/$(STAGE0) --dump-ir -o $@ $(SRCDIR)/main.c > $(OUT)/shecc-stage1.log
 	$(Q)chmod a+x $@

mk/arm.mk

@@ -1,21 +1,9 @@
-ifeq ($(HOST_ARCH),armv7l) # detect ARMv7-A only and assume Linux-compatible
-    TARGET_EXEC :=
-else
-    TARGET_EXEC = qemu-arm
-    TARGET_EXEC := $(shell which $(TARGET_EXEC))
-    ifndef TARGET_EXEC
-    $(warning "no qemu-arm found. Please check package installation")
-    ARM_EXEC = echo WARN: unable to run
-    endif
-endif
-
-export TARGET_EXEC
-
-arm-specific-defs = \
-    $(Q)$(PRINTF) \
-        "/* target: ARM */\n$\
-        \#pragma once\n$\
-        \#define ARCH_PREDEFINED \"__arm__\" /* defined by GNU C and RealView */\n$\
-        \#define ELF_MACHINE 0x28 /* up to ARMv7/Aarch32 */\n$\
-        \#define ELF_FLAGS 0x5000200\n$\
-        "
+ARCH_NAME = armv7l
+ARCH_QEMU = qemu-arm
+ARCH_DEFS = \
+    "/* target: ARM */\n$\
+    \#pragma once\n$\
+    \#define ARCH_PREDEFINED \"__arm__\" /* defined by GNU C and RealView */\n$\
+    \#define ELF_MACHINE 0x28 /* up to ARMv7/Aarch32 */\n$\
+    \#define ELF_FLAGS 0x5000200\n$\
+    "

mk/common.mk

@@ -5,8 +5,6 @@ else
     PRINTF = env printf
 endif
 
-HOST_ARCH = $(shell arch 2>/dev/null)
-
 # Control the build verbosity
 ifeq ("$(VERBOSE)","1")
     Q :=
@@ -23,3 +21,29 @@ PASS_COLOR = \e[32;01m
 NO_COLOR = \e[0m
 
 pass = $(PRINTF) "$(PASS_COLOR)$1 Passed$(NO_COLOR)\n"
+
+# Check the prerequisites
+PREREQ_LIST := dot jq
+TARGET_EXEC ?=
+ifneq ($(HOST_ARCH),$(ARCH_NAME))
+    # Add qemu to the list if the host and target architectures differ
+    PREREQ_LIST += $(ARCH_QEMU)
+    ifeq ($(filter $(ARCH_QEMU),$(notdir $(shell which $(ARCH_QEMU)))),)
+        STAGE1_WARN_MSG := "Warning: failed to build the stage 1 and $\
+                               stage 2 compilers due to missing $(ARCH_QEMU)\n"
+        STAGE1_CHECK_CMD := $(VECHO) $(STAGE1_WARN_MSG) && exit 1
+    endif
+
+    # Generate the path to the architecture-specific qemu
+    TARGET_EXEC = $(shell which $(ARCH_QEMU))
+endif
+export TARGET_EXEC
+
+PREREQ_EXEC := $(shell which $(PREREQ_LIST))
+PREREQ_MISSING := $(filter-out $(notdir $(PREREQ_EXEC)),$(PREREQ_LIST))
+
+ifdef PREREQ_MISSING
+    CONFIG_WARN_MSG := "Warning: missing packages: $(PREREQ_MISSING)\n$\
+                            Warning: Please check package installation\n"
+    CONFIG_CHECK_CMD := $(VECHO) $(CONFIG_WARN_MSG)
+endif

mk/riscv.mk

@@ -1,17 +1,10 @@
-TARGET_EXEC = qemu-riscv32
-TARGET_EXEC := $(shell which $(TARGET_EXEC))
-ifndef TARGET_EXEC
-$(warning "no qemu-riscv32 found. Please check package installation")
-TARGET_EXEC = echo WARN: unable to run
-endif
-
-export TARGET_EXEC
-
-riscv-specific-defs = \
-    $(Q)$(PRINTF) \
-        "/* target: RISCV */\n$\
-        \#pragma once\n$\
-        \#define ARCH_PREDEFINED \"__riscv\" /* Older versions of the GCC toolchain defined __riscv__ */\n$\
-        \#define ELF_MACHINE 0xf3\n$\
-        \#define ELF_FLAGS 0\n$\
-        "
+# Enforce the use qemu of by setting the ARCH_NAME variable to empty
+ARCH_NAME =
+ARCH_QEMU = qemu-riscv32
+ARCH_DEFS = \
+    "/* target: RISCV */\n$\
+    \#pragma once\n$\
+    \#define ARCH_PREDEFINED \"__riscv\" /* Older versions of the GCC toolchain defined __riscv__ */\n$\
+    \#define ELF_MACHINE 0xf3\n$\
+    \#define ELF_FLAGS 0\n$\
+    "