Linux C编译器从零开发一
基础程序汇编
test.c
int main() {return 42;
}查看反汇编
cc -o test test.c
objdump -d -M intel test
0000000000001129 <main>:1129: f3 0f 1e fa endbr64 112d: 55 push rbp112e: 48 89 e5 mov rbp,rsp1131: b8 2a 00 00 00 mov eax,0x2a1136: 5d pop rbp1137: c3 ret函数参数汇编
test.c
int plus(int x, int y) {
return x + y;
}int main() {
return plus(3, 4);
}.intel_syntax noprefix
.globl plus, mainplus:
add rsi, rdi
mov rax, rsi
retmain:
mov rdi, 3
mov rsi, 4
call plus
ret
.globl开头表示函数整个程序可见
call原理
- call将下一条指令（在本例中）ret的地址推入堆栈
- call跳转到作为参数给出的地址
自定义编译器编译基础程序
test.c
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv) {if (argc != 2) {fprintf(stderr, "Please input a Number:\n");return 1;}printf(".intel_syntax noprefix\n");printf(".globl main\n");printf("main:\n");printf(" mov rax, %d\n", atoi(argv[1]));printf(" ret\n");return 0;
}编译运行
cc -o test test.c
./test 42 > test.s
cc -o tmp test.s
./tmp
echo $?自定义编译器编译加减法程序
test.c
#include <stdio.h>
#include <stdlib.h>int main(int argc, char **argv) {if (argc != 2) {fprintf(stderr, "Please input a Number\n");return 1;}char *p = argv[1];printf(".intel_syntax noprefix\n");printf(".globl main\n");printf("main:\n");printf(" mov rax, %ld\n", strtol(p, &p, 10));// strtol读取数字，读完自动跳到下个符号while (*p) {if (*p == '+') {p++;printf(" add rax, %ld\n", strtol(p, &p, 10));continue;}if (*p == '-') {p++;printf(" sub rax, %ld\n", strtol(p, &p, 10));continue;}fprintf(stderr, "illegal sign '%c'\n", *p);return 1;}printf(" ret\n");return 0;
}编译
cc -o test test.c
./test 12+3+4 > tmp.s
cc -o tmp tmp.s
./tmp
echo $?
./test 1*3 > tmp.s //会提示非法符号测试
test.sh
#!/bin/bash
assert() {expected="$1"input="$2"./chibicc "$input" > tmp.s || exitgcc -static -o tmp tmp.s./tmpactual="$?"if [ "$actual" = "$expected" ]; thenecho "$input => $actual"elseecho "$input => $expected expected, but got $actual"exit 1fi
}assert 0 0
assert 42 42
assert 21 '5+20-4'echo OK参考
Compiler Explorer
创作不易，小小的支持一下吧！
