LLVM平台，短短几年间，改变了众多编程语言的走向，也催生了一大批具有特色的编程语言的出现，不愧为编译器架构的王者，也荣获2012年ACM软件系统奖 —— 题记
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简单的词法和语法分析
Lex和Yacc真是太好用了，非常方便我们构建一门语言的分析程序。
如果你对Lex和Yacc不了解的话，建议先看下我之前写的两篇文章，分别介绍了Lex和Yacc的用法。
Lex识别C风格字符串和注释
http://blog.csdn.net/xfxyy_sxfancy/article/details/45024573
创造新语言（2）——用Lex&Yacc构建简单的分析程序
http://blog.csdn.net/xfxyy_sxfancy/article/details/45046465
FLex创建一门语言的词法分析程序
我们创建的是一门编程语言，那么词法分析程序就不能像做实验一样那么草率，必须考虑周全，一般一门语言的词法分析程序大概需要囊括如下的几个方面：
识别关键字、识别标识符、识别基本常量（数字、浮点数、字符串、字符）、识别注释、识别运算符
这些都是非常重要的，而且是一门语言语法中必不可少的部分。
于是RedApple的词法分析部分，我就设计成了这样：
%{
#include <string>
#include "Model/nodes.h"
#include <list>
using namespace std;
#include "redapple_parser.hpp"
#include "StringEscape.h"
#define SAVE_TOKEN yylval.str = maketoken(yytext, yyleng)
#define SAVE_STRING yylval.str = makestring(yytext, yyleng, 2)
#define SAVE_STRING_NC yylval.str = makestring(yytext, yyleng, 3)
extern "C" int yywrap() { return 1; }
char* maketoken(const char* data, int len);
char* makestring(const char* data, int len, int s);
%}
%option yylineno
%%
"/*"([^*]|(*)*[^*/])*(*)*"*/" ; /* 就是这种注释 */
#[^
]*
; /* 井号注释 */
"//"[^
]*
; /* 双线注释 */
[ v
f] ; /* 过滤空白字符 */
"==" return CEQ;
"<=" return CLE;
">=" return CGE;
"!=" return CNE;
"<" return "<";
"=" return "=";
">" return ">";
"(" return "(";
")" return ")";
"[" return "[";
"]" return "]";
"{" return "{";
"}" return "}";
"." return ".";
"," return ",";
":" return ":";
";" return ";";
"+" return "+";
"-" return "-";
"*" return "*";
"/" return "/";
"%" return "%";
"^" return "^";
"&" return "&";
"|" return "|";
"~" return "~";
/* 宏运算符 */
"@" return "@";
",@" return MBK;
/* 下面声明要用到的关键字 */
/* 控制流 */
"if" return IF;
"else" return ELSE;
"while" return WHILE;
"do" return DO;
"goto" return GOTO;
"for" return FOR;
"foreach" return FOREACH;
/* 退出控制 */
"break"|"continue"|"exit" SAVE_TOKEN; return KWS_EXIT;
"return" return RETURN;
/* 特殊运算符 */
"new" return NEW;
"this" return THIS;
/* 特殊定义 */
"delegate" return DELEGATE;
"def" return DEF;
"define" return DEFINE;
"import" return IMPORT;
"using" return USING;
"namespace" return NAMESPACE;
"try"|"catch"|"finally"|"throw" SAVE_TOKEN; return KWS_ERROR; /* 异常控制 */
"null"|"true"|"false" SAVE_TOKEN; return KWS_TSZ; /* 特殊值 */
"struct"|"enum"|"union"|"module"|"interface"|"class" SAVE_TOKEN; return KWS_STRUCT; /* 结构声明 */
"public"|"private"|"protected" SAVE_TOKEN; return KWS_FWKZ; /* 访问控制 */
"const"|"static"|"extern"|"virtual"|"abstract"|"in"|"out" SAVE_TOKEN; return KWS_FUNC_XS; /* 函数修饰符 */
"void"|"double"|"int"|"float"|"char"|"bool"|"var"|"auto" SAVE_TOKEN; return KWS_TYPE; /* 基本类型 */
[a-zA-Z_][a-zA-Z0-9_]* SAVE_TOKEN; return ID; /* 标识符 */
[0-9]*.[0-9]* SAVE_TOKEN; return DOUBLE;
[0-9]+ SAVE_TOKEN; return INTEGER;
"(.|[^"])*" SAVE_STRING; return STRING; /* 字符串 */
@"(.|[^"])*" SAVE_STRING_NC; return STRING; /* 无转义字符串 */
"(.|.)" SAVE_STRING; return CHAR; /* 字符 */
. printf("Unknown Token!
"); yyterminate();
%%
char* maketoken(const char* data, int len) {
char* str = new char[len+1];
strncpy(str, data, len);
str[len] = 0;
return str;
}
char* makestring(const char* data, int len, int s) {
char* str = new char[len-s+1];
strncpy(str, data+s-1, len-s);
str[len-s] = 0;
if (s == 3) return str;
printf("source: %s
",str);
char* ans = CharEscape(str);
printf("escape: %s
",ans);
delete[] str;
return ans;
}
看起来非常的长，但主要多的就是枚举了大量的关键字和运算符，当然，这个你在开发一门语言的前期，不用面面俱到，可以选自己用到的先写，不足的再日后补充。
要注意，这里最难的应该就是：
"/*"([^*]|(*)*[^*/])*(*)*"*/" ; /* 就是这种注释 */
乍看起来，非常恐怖的正则式，但其实就是在枚举多种可能情况，来保障注释范围的正确性。
"/*" ( [^*] | (*)* [^*/] )* (*)* "*/" ; /* 就是这种注释 */
用Bison创建通用的语法分析程序
这里我编写的是类C语言的语法，要注意的是，很多情况会造成规约-规约冲突和移入-规约冲突。这里我简要介绍一个bison的工作原理。
这种算法在编译原理中，被称为LALR(1)分析法，是自底向上规约的算法之一，而且又会向前看一个token，Bison中的每一行，被称为一个产生式（或BNF范式）
例如下面这行：
def_module_statement : KWS_STRUCT ID "{" def_statements "}"
左边的是要规约的节点， 冒号右边是描述这个语法节点是用哪些节点产生的。
这是一个结构体定义的语法描述，KWS_STRUCT是终结符，来自Lex里的元素，看了上面的Lex描述，你应该能找到它的定义：
"struct"|"enum"|"union"|"module"|"interface"|"class" SAVE_TOKEN; return KWS_STRUCT; /* 结构声明 */
其实就是可能的一些关键字。而def_statements是另外的语法节点，由其他定义得来。
规约-规约冲突，是说，在当前产生式结束后，后面跟的元素还确定的情况下，能够规约到两个不同的语法节点:
def_module_statement : KWS_STRUCT ID "{" def_statements "}" ;
def_class_statement : KWS_STRUCT ID "{" def_statements "}" ;
statement : def_module_statement ";"
| def_class_statement ";"
;
以上文法便会产生规约-规约冲突，这是严重的定义错误，必须加以避免。
注意，我为了体现这个语法的错误，特意加上了上下文环境，不是说一样的语法定义会产生规约规约冲突，而是说后面可能跟的终结符都一样时，（在这里是’;’）才会产生规约规约冲突，所以避免这种问题也简单，就是把相似的语法节点合并在一起就可以了。
说道移入-规约冲突，就要谈起if-else的摇摆问题：
if_state : IF "(" expr ")" statement
| IF "(" expr ")" statement ELSE statement
;
statement : if_state
| ...
;
正如这个定义一样，在if的前半部识别完成后，下一个元素是ELSE终结符，此时可以规约，可以移入
说规约合法的理由是，if_state也是statement，而if第二条statement后面就是ELSE。
根据算法，这里规约是合理的，而移入同样是合理的。
为了避免这种冲突，一般Bison会优先选择移入，这样ELSE会和最近的IF匹配。
所以说，移入-规约冲突在你清楚的知道是哪的问题的时候，可以不加处理。但未期望的移入-规约冲突有可能让你的分析器不正确工作，这点还需要注意。
下面是我的Bison配置文件：
%{
#include "Model/nodes.h"
#include <list>
using namespace std;
#define YYERROR_VERBOSE 1
Node *programBlock; /* the top level root node of our final AST */
extern int yylex();
extern int yylineno;
extern char* yytext;
extern int yyleng;
void yyerror(const char *s);
%}
/* Represents the many different ways we can access our data */
%union {
Node *nodes;
char *str;
int token;
}
/* Define our terminal symbols (tokens). This should
match our tokens.l lex file. We also define the node type
they represent.
*/
%token <str> ID INTEGER DOUBLE
%token <token> CEQ CNE CGE CLE MBK
%token <token> "<" ">" "=" "+" "-" "*" "/" "%" "^" "&" "|" "~" "@"
%token <str> STRING CHAR
%token <token> IF ELSE WHILE DO GOTO FOR FOREACH
%token <token> DELEGATE DEF DEFINE IMPORT USING NAMESPACE
%token <token> RETURN NEW THIS
%token <str> KWS_EXIT KWS_ERROR KWS_TSZ KWS_STRUCT KWS_FWKZ KWS_FUNC_XS KWS_TYPE
/*
Define the type of node our nonterminal symbols represent.
The types refer to the %union declaration above. Ex: when
we call an ident (defined by union type ident) we are really
calling an (NIdentifier*). It makes the compiler happy.
*/
%type <nodes> program
%type <nodes> def_module_statement
%type <nodes> def_module_statements
%type <nodes> def_statement
%type <nodes> def_statements
%type <nodes> for_state
%type <nodes> if_state
%type <nodes> while_state
%type <nodes> statement
%type <nodes> statements
%type <nodes> block
%type <nodes> var_def
%type <nodes> func_def
%type <nodes> func_def_args
%type <nodes> func_def_xs
%type <nodes> numeric
%type <nodes> expr
%type <nodes> call_arg
%type <nodes> call_args
%type <nodes> return_state
//%type <token> operator 这个设计容易引起规约冲突，舍弃
/* Operator precedence for mathematical operators */
%left "~"
%left "&" "|"
%left CEQ CNE CLE CGE "<" ">" "="
%left "+" "-"
%left "*" "/" "%" "^"
%left "."
%left MBK "@"
%start program
%%
program : def_statements { programBlock = Node::getList($1); }
;
def_module_statement : KWS_STRUCT ID "{" def_statements "}" { $$ = Node::make_list(3, StringNode::Create($1), StringNode::Create($2), $4); }
| KWS_STRUCT ID ";" { $$ = Node::make_list(3, StringNode::Create($1), StringNode::Create($2), Node::Create()); }
;
def_module_statements : def_module_statement { $$ = Node::getList($1); }
| def_module_statements def_module_statement { $$ = $1; $$->addBrother(Node::getList($2)); }
;
func_def_xs : KWS_FUNC_XS { $$ = StringNode::Create($1); }
| func_def_xs KWS_FUNC_XS {$$ = $1; $$->addBrother(StringNode::Create($2)); }
;
def_statement : var_def ";" { $$ = $1; }
| func_def
| def_module_statement
| func_def_xs func_def { $$ = $2; $2->addBrother(Node::getList($1)); }
;
def_statements : def_statement { $$ = Node::getList($1); }
| def_statements def_statement { $$ = $1; $$->addBrother(Node::getList($2)); }
;
statements : statement { $$ = Node::getList($1); }
| statements statement { $$ = $1; $$->addBrother(Node::getList($2)); }
;
statement : def_statement
| expr ";" { $$ = $1; }
| block
| if_state
| while_state
| for_state
| return_state
;
if_state : IF "(" expr ")" statement { $$ = Node::make_list(3, StringNode::Create("if"), $3, $5); }
| IF "(" expr ")" statement ELSE statement { $$ = Node::make_list(4, StringNode::Create("if"), $3, $5, $7); }
;
while_state : WHILE "(" expr ")" statement { $$ = Node::make_list(3, StringNode::Create("while"), $3, $5); }
;
for_state : FOR "(" expr ";" expr ";" expr ")" statement { $$ = Node::make_list(5, StringNode::Create("for"), $3, $5, $7, $9); }
| FOR "(" var_def ";" expr ";" expr ")" statement { $$ = Node::make_list(5, StringNode::Create("for"), Node::Create($3), $5, $7, $9); }
;
return_state : RETURN ";" { $$ = StringNode::Create("return"); }
| RETURN expr ";" { $$ = StringNode::Create("return"); $$->addBrother($2); }
block : "{" statements "}" { $$ = Node::Create($2); }
| "{" "}" { $$ = Node::Create(); }
;
var_def : KWS_TYPE ID { $$ = Node::make_list(3, StringNode::Create("set"), StringNode::Create($1), StringNode::Create($2)); }
| ID ID { $$ = Node::make_list(3, StringNode::Create("set"), StringNode::Create($1), StringNode::Create($2)); }
| KWS_TYPE ID "=" expr { $$ = Node::make_list(4, StringNode::Create("set"), StringNode::Create($1), StringNode::Create($2), $4); }
| ID ID "=" expr { $$ = Node::make_list(4, StringNode::Create("set"), StringNode::Create($1), StringNode::Create($2), $4); }
;
func_def : ID ID "(" func_def_args ")" block
{ $$ = Node::make_list(5, StringNode::Create("function"), StringNode::Create($1), StringNode::Create($2), $4, $6); }
| KWS_TYPE ID "(" func_def_args ")" block
{ $$ = Node::make_list(5, StringNode::Create("function"), StringNode::Create($1), StringNode::Create($2), $4, $6); }
| ID ID "(" func_def_args ")" ";"
{ $$ = Node::make_list(5, StringNode::Create("function"), StringNode::Create($1), StringNode::Create($2), $4); }
| KWS_TYPE ID "(" func_def_args ")" ";"
{ $$ = Node::make_list(5, StringNode::Create("function"), StringNode::Create($1), StringNode::Create($2), $4); }
;
func_def_args : var_def { $$ = Node::Create(Node::Create($1)); }
| func_def_args "," var_def { $$ = $1; $$->addChildren(Node::Create($3)); }
| %empty { $$ = Node::Create(); }
;
numeric : INTEGER { $$ = IntNode::Create($1); }
| DOUBLE { $$ = FloatNode::Create($1); }
;
expr : expr "=" expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create("="), $1, $3); }
| ID "(" call_args ")" { $$ = Node::make_list(2, StringNode::Create("call"), StringNode::Create($1)); $$->addBrother($3); }
| ID { $$ = IDNode::Create($1); }
| numeric { $$ = $1; }
| STRING { $$ = StringNode::Create($1); }
| KWS_TSZ
| NEW ID "(" call_args ")" { $$ = Node::make_list(3, StringNode::Create("new"), StringNode::Create($2), $4); }
| expr CEQ expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create("=="), $1, $3); }
| expr CNE expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create("!="), $1, $3); }
| expr CLE expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create("<="), $1, $3); }
| expr CGE expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create(">="), $1, $3); }
| expr "<" expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create("<"), $1, $3); }
| expr ">" expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create(">"), $1, $3); }
| expr "+" expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create("+"), $1, $3); }
| expr "-" expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create("-"), $1, $3); }
| expr "*" expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create("*"), $1, $3); }
| expr "/" expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create("/"), $1, $3); }
| expr "%" expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create("%"), $1, $3); }
| expr "^" expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create("^"), $1, $3); }
| expr "&" expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create("&"), $1, $3); }
| expr "|" expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create("|"), $1, $3); }
| expr "." expr { $$ = Node::make_list(4, StringNode::Create("opt2"), StringNode::Create("."), $1, $3); }
| "~" expr { $$ = Node::make_list(4, StringNode::Create("opt1"), StringNode::Create("~"), $2); }
| "(" expr ")" /* ( expr ) */ { $$ = $2; }
;
call_arg : expr { $$ = $1; }
| ID ":" expr { $$ = Node::make_list(3, StringNode::Create(":"), $1, $3); }
;
call_args : %empty { $$ = Node::Create(); }
| call_arg { $$ = Node::getList($1); }
| call_args "," call_arg { $$ = $1; $$->addBrother(Node::getList($3)); }
;
%%
void yyerror(const char* s){
fprintf(stderr, "%s
", s);
fprintf(stderr, "line %d: ", yylineno);
fprintf(stderr, "text %s
", yytext);
exit(1);
}