(四)基於Flex設計實現C子集的詞法分析器

技術 · 發表 2019-02-19 14:52:02

摘要：前期準備為了寫出C子集的詞法分析器，首先應該瞭解C子集有哪些。參考C 基本語法(菜鳥教程) 先進行總結：數字需要考慮到十進位制、十六進位制、八進位制、二進位制、正負數、小數、科學計數法以及...

前期準備

為了寫出C子集的詞法分析器，首先應該瞭解C子集有哪些。

數字

需要考慮到十進位制、十六進位制、八進位制、二進位制、正負數、小數、科學計數法以及一些數字字尾：u，l，f等（注意浮點數不能加uU）。（應該沒了吧？）

關鍵字：

auto、break、case、char、const、continue、default、do、double、else、enum、extern、float、for、goto、if、int、long、register、return、short、signed、sizeof、static、struct、switch、typedef、unsigned、union、void、volatile、while。

識別符號：

C 識別符號是用來標識變數、函式，或任何其他使用者自定義專案的名稱。一個識別符號以字母 A-Z 或 a-z 或下劃線 _ 開始，後跟零個或多個字母、下劃線和數字（0-9）。

運算子：

算數運算子：+、-、*、/、%、++、--

關係運算符：==、!=、>、<、>=、<=

邏輯運算子：&&、||、!

位運算子：&、|、^、～、<<、>>

賦值運算子：=、+=、-=、*=、/=、%=、<<=、>>=、&=、^=、|=

雜項運算子我覺得單憑flex無法實現。

標點符號

三種括號：{}[]() 以及 :,;.-> " '

（應該沒了吧？）

flex程式碼實現

$ cat C-lexical-analyzer.l 
%{
#include<stdio.h>
%}

/*數字定義*/
/*科學計數表示*/
science {decimal}(\.[0-9]+)?([Ee][-+]?[0-9]+)?
/*十進位制*/
decimal ([-+])?(0|[1-9][0-9]*)
/*十六進位制*/
hexadecimal 0[xX][a-fA-F0-9]+
/*二進位制*/
binary 0[bB][01]+
/*八進位制*/
octal 0[0-7]+
/*總表示*/
number ({hexadecimal}|{binary}|{science}|{octal})(([uU]?[Ll]?)|([Ll]?[Uu]?)|([fF]?))
/*注意浮點數總是有符號，不需要Uu字尾，所以在接下來單做一個浮點數異常處理*/
/*數字異常處理*/
floatexcption {decimal}\.([0-9]+)?([Ee][-+]?[0-9]+)?[Uu]
excption [0-9][0-9a-zA-Z\.]+

/*關鍵字*/
AUTO auto 
BREAK break
CASE case
CHAR char
CONST const
CONTINUE continue
DEFAULT default
DO do
DOUBLE double
ELSE else
ENUM enum
EXTERN extern
FLOAT float
FOR for
GOTO goto
IF if
INT int
LONG long 
REGISTER register
RETURN return
SHORT short
SIGNED signed
SIZEOF sizeof
STATIC static
STRUCT struct
SWITCH switch
TYPEDEF typedef
UNSIGNED unsigned
UNION union
VOID void 
VOLATILE volatile
WHILE while

/*識別符號定義*/
identifier [a-z_A-Z][a-z_A-Z0-9]*

/*其它字元*/
whitespace [ \t\n\r\f\v]+
errno .
 
 /*運算子*/
 /*算術運算子*/
ADD\+
SUB\-
MUL\*
QUO\/
REM%
INC\+\+
DEC\-\-
 /*賦值運算子*/
ASSIGN=
ADD_ASSIGN\+=
SUB_ASSIGN\-=
MUL_ASSIGN\*=
QUO_ASSIGN\/=
REM_ASSIGN%=
AND_ASSIGN\&=
OR_ASSIGN\|=
XOR_ASSIGN\^=
SHL_ASSIGN<<=
SHR_ASSIGN>>=
AND_NOT_ASSIGN~=
 /*位運算子*/
AND&
OR\|
XOR\^
SHL<<
SHR>>
AND_NOT~
 /*邏輯運算子*/
LAND&&
LOR\|\|
NOT\!
 /*關係運算符*/
EQL==
LSS<
GTR>
NEQ!=
LEQ<=
GEQ>=
 /*標點符號*/
LPAREN\(
LBRACK\[
LBRACE\{
COMMA,
PERIOD\.
RPAREN\)
RBRACK\]
RBRACE\}
SEMICOLON;
COLON:
POT\->
DQUA\"
SQUA\'
%%
 
 /*關鍵字*/
{AUTO} {printf("Key Word:%s\n",yytext);}
{BREAK} {printf("Key Word:%s\n",yytext);}
{CASE} {printf("Key Word:%s\n",yytext);}
{CHAR} {printf("Key Word:%s\n",yytext);}
{CONST} {printf("Key Word:%s\n",yytext);}
{CONTINUE} {printf("Key Word:%s\n",yytext);}
{DEFAULT} {printf("Key Word:%s\n",yytext);}
{DO} {printf("Key Word:%s\n",yytext);}
{DOUBLE} {printf("Key Word:%s\n",yytext);}
{ELSE} {printf("Key Word:%s\n",yytext);}
{ENUM} {printf("Key Word:%s\n",yytext);}
{EXTERN} {printf("Key Word:%s\n",yytext);}
{FLOAT} {printf("Key Word:%s\n",yytext);}
{FOR} {printf("Key Word:%s\n",yytext);}
{GOTO} {printf("Key Word:%s\n",yytext);}
{IF} {printf("Key Word:%s\n",yytext);}
{INT} {printf("Key Word:%s\n",yytext);}
{LONG} {printf("Key Word:%s\n",yytext);}
{REGISTER} {printf("Key Word:%s\n",yytext);}
{RETURN} {printf("Key Word:%s\n",yytext);}
{SHORT} {printf("Key Word:%s\n",yytext);}
{SIGNED} {printf("Key Word:%s\n",yytext);}
{SIZEOF} {printf("Key Word:%s\n",yytext);}
{STATIC} {printf("Key Word:%s\n",yytext);}
{STRUCT} {printf("Key Word:%s\n",yytext);}
{SWITCH} {printf("Key Word:%s\n",yytext);}
{TYPEDEF} {printf("Key Word:%s\n",yytext);}
{UNSIGNED} {printf("Key Word:%s\n",yytext);}
{UNION} {printf("Key Word:%s\n",yytext);}
{VOID} {printf("Key Word:%s\n",yytext);}
{VOLATILE} {printf("Key Word:%s\n",yytext);}
{WHILE} {printf("Key Word:%s\n",yytext);}

 /*提前處理浮點數+uU的異常*/
{floatexcption} {printf("Float Execption: %s\n",yytext);} 
 /*數字表示*/
{number} {printf("Number:%s\n",yytext);}
 /*異常數字處理*/
{excption} {printf("Number Execption:%s\n",yytext);}

 /*跳過空白*/
{whitespace} {}

 /*運算子*/
 /*算術運算子*/
{ADD} {printf("Operator:%s\n",yytext);}
{SUB} {printf("Operator:%s\n",yytext);}
{MUL} {printf("Operator:%s\n",yytext);}
{QUO} {printf("Operator:%s\n",yytext);}
{REM} {printf("Operator:%s\n",yytext);}
{INC} {printf("Operator:%s\n",yytext);}
{DEC} {printf("Operator:%s\n",yytext);}
 /*邏輯運算子*/
{LAND} {printf("Operator:%s\n",yytext);}
{LOR} {printf("Operator:%s\n",yytext);}
{NOT} {printf("Operator:%s\n",yytext);}
 /*賦值運算子*/
{ASSIGN} {printf("Operator:%s\n",yytext);}
{ADD_ASSIGN} {printf("Operator:%s\n",yytext);}
{SUB_ASSIGN} {printf("Operator:%s\n",yytext);}
{MUL_ASSIGN} {printf("Operator:%s\n",yytext);}
{QUO_ASSIGN} {printf("Operator:%s\n",yytext);}
{REM_ASSIGN} {printf("Operator:%s\n",yytext);}
{AND_ASSIGN} {printf("Operator:%s\n",yytext);}
{OR_ASSIGN} {printf("Operator:%s\n",yytext);}
{XOR_ASSIGN} {printf("Operator:%s\n",yytext);}
{SHL_ASSIGN} {printf("Operator:%s\n",yytext);}
{SHR_ASSIGN} {printf("Operator:%s\n",yytext);}
{AND_NOT_ASSIGN} {printf("Operator:%s\n",yytext);}
 /*位運算子*/
{AND} {printf("Operator:%s\n",yytext);}
{OR} {printf("Operator:%s\n",yytext);}
{XOR} {printf("Operator:%s\n",yytext);}
{SHL} {printf("Operator:%s\n",yytext);}
{SHR} {printf("Operator:%s\n",yytext);}
{AND_NOT} {printf("Operator:%s\n",yytext);}
 /*關係運算符*/
{EQL} {printf("Operator:%s\n",yytext);}
{LSS} {printf("Operator:%s\n",yytext);}
{GTR} {printf("Operator:%s\n",yytext);}
{NEQ} {printf("Operator:%s\n",yytext);}
{LEQ} {printf("Operator:%s\n",yytext);}
{GEQ} {printf("Operator:%s\n",yytext);}
 /*標點符號*/
{LPAREN} {printf("Punctuation:%s\n",yytext);}
{LBRACK} {printf("Punctuation:%s\n",yytext);}
{LBRACE} {printf("Punctuation:%s\n",yytext);}
{COMMA} {printf("Punctuation:%s\n",yytext);}
{PERIOD} {printf("Punctuation:%s\n",yytext);}
{RPAREN} {printf("Punctuation:%s\n",yytext);}
{RBRACK} {printf("Punctuation:%s\n",yytext);}
{RBRACE} {printf("Punctuation:%s\n",yytext);}
{SEMICOLON} {printf("Punctuation:%s\n",yytext);}
{COLON} {printf("Punctuation:%s\n",yytext);}
{POT} {printf("Punctuation:%s\n",yytext);}
{DQUA} {printf("Punctuation:%s\n",yytext);}
{SQUA} {printf("Punctuation:%s\n",yytext);}


{identifier} {printf("ID:%s\n",yytext);}
{errno} {printf("Mystery character:%s\n",yytext);}
%%
int main(int argc,char **argv)
{
yylex();
return 0;
}
int yywarp(){
return 1;
}

測試效果：

$ ./start.sh#編譯指令碼
編譯完成，請手動執行C-lexical-analyzer

[jin1ming@ML C-Lex]$ ./C-lexical-analyzer 
78.987e76f
Number:78.987e76f
adsda
ID:adsda
srg090
ID:srg090
_12
ID:_12
!@#$#
Operator:!
Mystery character:@
Mystery character:#
Mystery character:$
Mystery character:#
121qwqer
Number Execption:121qwqer
1.2.
Number Execption:1.2.
1.2uf
Number Execption:1.2uf
==
Operator:==
-
Operator:-
=
Operator:=
^
Operator:^
!
Operator:!
>>
Operator:>>
,.!
Punctuation:,
Punctuation:.
Operator:!

(四)基於Flex設計實現C子集的詞法分析器

前期準備

flex程式碼實現

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