# HG changeset patch
# User John Tsiombikas <nuclear@member.fsf.org>
# Date 1426391264 -7200
# Node ID 10f07b308aab9c6ade37dc2d09d767e6cad74d65

tutor2.txt completed

diff -r 000000000000 -r 10f07b308aab .hgignore
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/.hgignore	Sun Mar 15 05:47:44 2015 +0200
@@ -0,0 +1,5 @@
+\.o$
+\.s$
+\.swp$
+^test$
+^a\.out$
diff -r 000000000000 -r 10f07b308aab COMPILE
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/COMPILE	Sun Mar 15 05:47:44 2015 +0200
@@ -0,0 +1,5 @@
+#!/bin/sh
+
+./test >out.s && \
+	as --32 -o out.o out.s && \
+	ld -m elf_i386 out.o
diff -r 000000000000 -r 10f07b308aab Makefile
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Makefile	Sun Mar 15 05:47:44 2015 +0200
@@ -0,0 +1,12 @@
+src = $(wildcard src/*.c)
+obj = $(src:.c=.o)
+bin = test
+
+CFLAGS = -pedantic -Wall -g
+
+$(bin): $(obj)
+	$(CC) -o $@ $(obj) $(LDFLAGS)
+
+.PHONY: clean
+clean:
+	rm -f $(obj) $(bin)
diff -r 000000000000 -r 10f07b308aab RUN
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/RUN	Sun Mar 15 05:47:44 2015 +0200
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+./a.out; echo $?
diff -r 000000000000 -r 10f07b308aab src/main.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/main.c	Sun Mar 15 05:47:44 2015 +0200
@@ -0,0 +1,230 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include <stdarg.h>
+
+void init(void);
+void expression(void);
+void term(void);
+void factor(void);
+void add(void);
+void sub(void);
+void mul(void);
+void divide(void);
+void get_char(void);
+void match(char c);
+char get_name(void);
+char get_num(void);
+void stop(const char *s, ...);
+void expected(const char *s);
+void emit(const char *fmt, ...);
+void vemit(const char *fmt, va_list ap);
+void emitln(const char *fmt, ...);
+int is_addsub(char c);
+
+FILE *infile, *outfile;
+char look;
+
+static const char *prologue =
+	"\t.globl _start\n"
+	"_start:\n"
+	"\tcall main\n"
+	"\tmov %eax, %ebx\n"
+	"\tmov $1, %eax\n"
+	"\tint $0x80\n"
+	"main:\n"
+	"\t# ---- START ----\n";
+
+static const char *epilogue = "\t# ---- END ----\n\tret\n";
+
+int main(void)
+{
+	infile = stdin;
+	outfile = stdout;
+
+	init();
+	/* output prologue */
+	fputs(prologue, outfile);
+
+	expression();
+
+	/* output epilogue */
+	fputs(epilogue, outfile);
+	return 0;
+}
+
+void init(void)
+{
+	get_char();
+}
+
+void expression(void)
+{
+	if(is_addsub(look)) {
+		emitln("xor %%eax, %%eax");
+	} else {
+		term();
+	}
+
+	while(is_addsub(look)) {
+		emitln("push %%eax");
+		switch(look) {
+		case '+':
+			add();
+			break;
+		case '-':
+			sub();
+			break;
+		default:
+			expected("addop");
+		}
+	}
+}
+
+void term(void)
+{
+	factor();
+	while(look == '*' || look == '/') {
+		emitln("push %%eax");
+		switch(look) {
+		case '*':
+			mul();
+			break;
+		case '/':
+			divide();
+			break;
+		default:
+			expected("mulop");
+		}
+	}
+}
+
+void factor(void)
+{
+	if(look == '(') {
+		match('(');
+		expression();
+		match(')');
+	} else {
+		emitln("mov $%c, %%eax", get_num());
+	}
+}
+
+void add(void)
+{
+	match('+');
+	term();
+	emitln("pop %%ebx");
+	emitln("add %%ebx, %%eax");
+}
+
+void sub(void)
+{
+	match('-');
+	term();
+	emitln("pop %%ebx");
+	emitln("sub %%ebx, %%eax");
+	emitln("neg %%eax");
+}
+
+void mul(void)
+{
+	match('*');
+	factor();
+	emitln("pop %%ebx");
+	emitln("imul %%ebx");
+}
+
+void divide(void)
+{
+	match('/');
+	factor();
+	emitln("mov %%eax, %%ebx");
+	emitln("pop %%eax");
+	emitln("idiv %%ebx");
+}
+
+void get_char(void)
+{
+	look = fgetc(infile);
+}
+
+void match(char c)
+{
+	if(look == c) {
+		get_char();
+	} else {
+		char s[2] = {0, 0};
+		s[0] = c;
+		expected(s);
+	}
+}
+
+char get_name(void)
+{
+	char res;
+	if(!isalpha(look)) {
+		expected("name");
+	}
+	res = toupper(look);
+	get_char();
+	return res;
+}
+
+char get_num(void)
+{
+	char res;
+	if(!isdigit(look)) {
+		expected("integer");
+	}
+	res = look;
+	get_char();
+	return res;
+}
+
+void stop(const char *s, ...)
+{
+	va_list ap;
+
+	fprintf(stderr, "error: ");
+	va_start(ap, s);
+	vfprintf(stderr, s, ap);
+	va_end(ap);
+	fputc('\n', stderr);
+
+	abort();
+}
+
+void expected(const char *s)
+{
+	stop("%s expected", s);
+}
+
+void emit(const char *fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	vemit(fmt, ap);
+	va_end(ap);
+}
+
+void vemit(const char *fmt, va_list ap)
+{
+	fputc('\t', outfile);
+	vfprintf(outfile, fmt, ap);
+}
+
+void emitln(const char *fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	vemit(fmt, ap);
+	va_end(ap);
+	fputc('\n', outfile);
+}
+
+
+int is_addsub(char c)
+{
+	return c == '+' || c == '-';
+}