Writing-A-C-Complier

编译指令

C源码→汇编
gcc -S -O -fno-asynchronous-unwind-tables -fcf-protection=none xxx.c

汇编→执行文件
gcc xxx.s -o xxx

C源码->预处理文件
gcc -E -P xxx.c -O xxx.i

The lexer

int A keyword
main An identifier, whose value is “main”
( An open parenthesis
void A keyword
) A close parenthesis
{ An open brace
return A keyword
2 A constant, whose value is “2”
; A semicolon
} A close brace

identifier(标识符): ascii字母或下划线开头的，跟着一堆字母/下划线/数字；大小写敏感

integer constant（整形常量）：一个或多个数字

each token type with a regular expression， or regex

Token IRegular expression
Identifier [a-zA-Z_]\w*\b
Constant [0-9]+\b
int keyword int\b
void keyword void\b
return keyword return\b
Open parenthesis \(
Close parenthesis \)
Open brace {
Close brace }
Semicolon ;