CODEWITHSUNDEEP
c++stringbisonflex-lexer
ghostmansd
ghostmansd

Reputation: 3455

flex and bison: string literal

I need your advice on how to get string literal. String literals is everything what starts with b", has zero or more symbols then and ends with ". Token is called BYTES_OBJECT. bytes_type is a name of type which stores such string literals. Here is what I've tried:

{%
#include "parser.hpp"
#include <iostream>
#include <string>
string BUFFER;
%}

%option noyywrap
%x COMMENT
%x BYTESMODE

"b"[\"] {
  BUFFER = string();
  BEGIN BYTESMODE;
} // BYTESMODE

  <BYTESMODE>{BYTES_HEXCODE} {
    // convert to hexcode
  } // BYTES_HEXCODE

  <BYTESMODE>{BYTES_ESCAPE} {
    yytext++; // Move to the next char
    switch (*yytext) {
      case '\'': BUFFER += '\''; break;
      case '\"': BUFFER += '\"'; break;
      case '\\': BUFFER += '\\'; break;
      case '\?': BUFFER += '?';  break;
      case 'a':  BUFFER += '\a'; break;
      case 'b':  BUFFER += '\b'; break;
      case 'f':  BUFFER += '\f'; break;
      case 'n':  BUFFER += '\n'; break;
      case 'r':  BUFFER += '\r'; break;
      case 't':  BUFFER += '\t'; break;
      case 'v':  BUFFER += '\v'; break;
    } // end of switch
  } // BYTES_ESCAPE

  <BYTESMODE>[^\"] {
    BUFFER += yytext;
  } // BYTES_SYMBOL

  <BYTESMODE>\" {
    bytes_type object = BUFFER;
    yylval.bytes_buffer = &object;
    BEGIN INITIAL;
    return BYTES_OBJECT;
  } // closing quote

However, when I try to create string, it cause segment fault. If return BYTES_OBJECT is before BEGIN INITIAL, it processes literals incorrect. How can I solve it? I guess that even concept can be done more easy than I've written.

Thanks in advance!

Upvotes: 1

Views: 1783

Answers (1)

perreal
perreal

Reputation: 97918

Your input file has some errors. You should not be doing such detailed handling just to recognize strings. A simpler example:

%option noyywrap
%{
#include <iostream>
#include <string>
%}

%%
b\"(\\.|[^\\"])*\" { 
  std::cout << "string:" << yytext << std::endl;
  return(1); 
}

%%

int main() {
  yylex();
  return 0;
}

Upvotes: 1

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