+++
date = '2025-02-15T16:55:11+08:00'
draft = true
title = 'NJU ICS PA Notes'

+++

One may encounter some hurdles here and there when drilling through [NJU ICS PA 2024](https://nju-projectn.github.io/ics-pa-gitbook/ics2024/), which is surely a very good educational project btw. So here's my two cents.

## Makefiles Spaghetti

- `Q := @`: The `@` symbol in a Makefile is used to suppress the command echoing. When `Q` is used before a command, it prevents the command from being printed to the terminal before execution.
- In a Makefile, `:=` and `=` are used to define variables, but they behave differently:
  - `=` (Recursive or Lazy Assignment): The value is expanded when the variable is used, not when it is defined.
  - `:=` (Simple or Immediate Assignment): The value is expanded immediately when the variable is defined.
- `::` is a double colon rule, which allows multiple rules for the same target. Each rule is treated independently.

Makefile for compile menuconfig is at `nemu/scripts/config.mk`.

All the source file names are gathered from `filelist.mk` under `nemu/src`.

```makefile
# Include all filelist.mk to merge file lists
FILELIST_MK = $(shell find -L ./src -name "filelist.mk")
include $(FILELIST_MK)
```

And all `.c` files under `DIRS-y` will be added to `SRCS-y`.

```makefile
SRCS-y += $(shell find -L $(DIRS-y) -name "*.c")
```

NEMU Compilation happens at `nemu/scripts/build.mk`.

```makefile
OBJS = $(SRCS:%.c=$(OBJ_DIR)/%.o) $(CXXSRC:%.cc=$(OBJ_DIR)/%.o)

# Compilation patterns
$(OBJ_DIR)/%.o: %.c
	@echo + CC $<
	@mkdir -p $(dir $@)
	@$(CC) $(CFLAGS) -c -o $@ $<
	$(call call_fixdep, $(@:.o=.d), $@)

$(OBJ_DIR)/%.o: %.cc
	@echo + CXX $<
	@mkdir -p $(dir $@)
	@$(CXX) $(CFLAGS) $(CXXFLAGS) -c -o $@ $<
	$(call call_fixdep, $(@:.o=.d), $@)
```

Which is included by `nemu/scripts/native.mk` along with target `run` and `gdb` etc.