initial asm file

.gitignore

@@ -1 +1,2 @@
 /.direnv/
+lang/target

flake.nix

@@ -23,8 +23,15 @@
       devShells.default = pkgs.mkShell {
         buildInputs = [
           pkg-config
+          man-pages
           mold
           clang
+          clang-tools
+          just
+          just-formatter
+          just-lsp
+          gdb
+          gdbgui
           nasm
           nasmfmt
           git

lang/Makefile

@@ -0,0 +1,25 @@
+# Makefile: Compile and link main.asm using nasm and mold, intermediate files in target/
+
+TARGET_DIR := target
+SRC := src/main.asm
+OBJ := $(TARGET_DIR)/main.o
+BIN := $(TARGET_DIR)/main
+
+.PHONY: all clean
+
+all: $(BIN)
+
+$(TARGET_DIR):
+	mkdir -p $(TARGET_DIR)
+
+$(OBJ): $(SRC) | $(TARGET_DIR)
+	nasm -f elf64 -g $(SRC) -o $(OBJ)
+
+$(BIN): $(OBJ)
+	mold -run ld -o $(BIN) $(OBJ)
+
+run: $(BIN)
+	$(BIN)
+
+clean:
+	rm -rf $(TARGET_DIR)

lang/src/main.asm

@@ -0,0 +1,51 @@
+;; Compile with:
+;; nasm -f elf64 main.asm -o main.o
+
+;; RO section
+section .data
+    hello_msg db "Hello, World!", 10
+    hello_msg_len equ $ - hello_msg
+    die_msg db "panic occured!", 10
+    die_msg_len equ $ - die_msg
+
+section .text
+global _start
+
+_start:
+    ; get filename from argv[1]
+    ; argv is at rsp + 8
+    ; check if argc > 1
+    mov rdx, hello_msg
+    mov rcx, hello_msg_len
+    call eprint_str
+    mov rax, [rsp]        ; argc
+    cmp rax, 1
+    jle .no_filename      ; if argc <= 1, no filename provided
+    mov rax, 42
+    ret
+
+
+.no_filename:
+    call die
+
+die:
+    mov rdx, die_msg
+    mov rcx, die_msg_len
+    call eprint_str
+    ; exit with error code 1
+    mov rax, 60          ; syscall: exit
+    mov rdi, 1           ; status: 1
+    syscall
+    ret                         ; should never reach here
+
+eprint_str:                      ; print string-length pair to stderr
+    ; str pointer in rdx
+    ; length in rcx
+    mov rax, 1           ; syscall: write
+    mov rdi, 2           ; fd: stderr
+    mov rsi, rdx         ; buf: str
+    mov rdx, rcx         ; len: length
+    syscall
+    ret
+    
+