检查中未完成的弯曲评论 [英] checking unfinished comments in flex

问题描述

我是一个新的弯曲。我刚写了一个样本code检测多线使用柔性程序的意见。现在我想改善code。我想检测在code未完成和虐待形成意见。例如：注释开头没有一个结局* /是一个未完成的注释并形成不良评论我的意思是注释不正确形成/ *，也就是说，一个EOF出现里面的评论等等。我有我的$添加C $ C到检查这些东西呢？我的示例code是如下：

 ％×COMMENT_MULTI_LINE
％{
字符* commentStart;
％}%%[\\ n \\ t \\ r] + {
  / *忽略空白* /}
＆LT;初始＆GT;/ *{
  commentStart = yytext中;
  BEGIN（COMMENT_MULTI_LINE）;
}＆所述; COMMENT_MULTI_LINE＆gt;中* /{
  字符*注释= strndup（commentStart，yytext中+ 2  -  commentStart）;
  的printf（％s'的：是一个多行注释\\ n，评论）;
  免费（注解）;
  BEGIN（INITIAL）;
}＆所述; COMMENT_MULTI_LINE取代。 {}＆LT; COMMENT_MULTI_LINE＆GT; \\ N {}
%%INT主（INT ARGC，CHAR *的argv []）{
  函数yylex（）;
}
 

解决方案

柔性手册章节关于使用＆LT;＆LT; EOF＆GT;＆GT; 是相当有帮助的，因为它具有完全相同的情况下，作为一个例子，他们的code也可以复制逐字到Flex程序。

，因为它解释，使用时＆LT;＆LT; EOF＆GT;＆GT; 你不能将其放置在一个正常的常规EX pression 的模式。它只能通过的状态的名称来进行。在您的code你正在使用的状态，表明你是一个注释中。这种状态称为 COMMENT_MULTI 。所有你需要做的就是把这些在＆LT面前;＆LT; EOF＆GT;＆GT; 标记，并给它一个动作做的：

 ＆LT; COMMENT_MULTI＆GT;＆LT;＆LT;＆EOF GT;＆GT; {printf的（未终止的点评：％S \\ n，yytext中）;
                        yyterminate（）;}
 

专项行动功能 yyterminate（）告诉弯曲你已经认识到＆LT;＆LT; EOF＆GT;＆GT; ，它标志着你的程序结束时的输入。

我已经测试过这一点，它在你的code工作。 （和多线串也）。

I am a new to flex. I have just written a sample code to detect multi line comments using a flex program. Now I want to improve the code. I want to detect unfinished and ill formed comments in the code. for example: a comment beginning with /* without an ending */ is an unfinished comment and by ill formed comment I mean the comment is not properly formed, say, an EOF appears inside the comment etc. What I have to add in my code to check these things? My sample code is as follows:

%x COMMENT_MULTI_LINE
%{
char* commentStart;
%}

%%

[\n\t\r ]+ { 
  /* ignore whitespace */ }


<INITIAL>"/*" { 
  commentStart = yytext; 
  BEGIN(COMMENT_MULTI_LINE); 
}

<COMMENT_MULTI_LINE>"*/" { 
  char* comment = strndup(commentStart, yytext + 2 - commentStart);
  printf("'%s': was a multi-line comment\n", comment);
  free(comment); 
  BEGIN(INITIAL); 
}

<COMMENT_MULTI_LINE>. { 

} 

<COMMENT_MULTI_LINE>\n { 

} 


%%

int main(int argc, char *argv[]){    
  yylex();         
}

解决方案

The flex manual section on using <<EOF>> is quite helpful as it has exactly your case as an example, and their code can also be copied verbatim into your flex program.

As it explains, when using <<EOF>> you cannot place it in a normal regular expression pattern. It can only be proceeded by a the name of a state. In your code you are using a state to indicate you are inside a comment. This state is called COMMENT_MULTI. All you have to do is put that in front of the <<EOF>> marker and give it an action to do:

<COMMENT_MULTI><<EOF>> {printf("Unterminated Comment: %s\n", yytext); 
                        yyterminate();}

The special action function yyterminate() tells flex that you have recognised the <<EOF>> and that it marks the end-of-input for your program.

I have tested this, and it works in your code. (And with multi-line strings also).

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