Flex and Bison Problems

Jakman217 (18)
I'm working on a interpreter for a class and I it's nearly done, but I seem to have somehow entered an infinite loop or some bug that won't run through minor interpretation. All the first level interpretation is done by FLEX and most of it is like this.

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"("			{
			printf("TOKEN: LPAREN    LEXEME: %s\n", yytext);
			return T_LPAREN;
			}


From there it Bison works on the grammatical stuff. It should be able to do simple evaluation procedures like add, subtract, divide. Stuff like that.

There are no errors in the compiling and for some reason it stops before even the first token is output to the screen. Can anyone think of any reason it would be like this?

I'll put the a majority of the code below. It's a bit lengthy.

Flex file
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/*    mfpl.l
 
 	Specifications of tokens for the MFPL language.
 */

%{
%}

/*
 *	Definitions of regular expressions
*/

WSPACE		[ \t\r]+
NEWLINE          \n
LO_ALPHA		[a-z]
HI_ALPHA		[A-Z]
ALPHA			{LO_ALPHA}|{HI_ALPHA}
DIGIT            [0-9]
ALPHANUM		{ALPHA}|{DIGIT}
UNDERSCORE		_

IDENT			({UNDERSCORE}|{ALPHA})({ALPHANUM}|{UNDERSCORE})*

NEG_INTCONST	"-"[0-9]+
POS_INTCONST	("+")?[0-9]+
INTCONST        {NEG_INTCONST}|{POS_INTCONST}

DOUBLE_QUOTE      \"
STRCONST         {DOUBLE_QUOTE}[^\"\n]*{DOUBLE_QUOTE} 

COMMENT           ";".*$      
/*
 *	Tokens
*/
%%

%%


Bison File
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/*
      mfpl.y

 	Specifications for the MFPL language, YACC input file.

      To create syntax analyzer:

        flex mfpl.l
        bison mfpl.y
        g++ mfpl.tab.c -o mfpl_parser
        mfpl_parser < inputFileName
 */

/*
 *	Declaration section.
 */
%{
#include <stdio.h>
#include "SymbolTable.h"
#include <stack>
#include <string>
#include <iostream>
using namespace std;

// type codes
#define UNDEFINED         -1
#define FUNCTION           0
#define INT                1
#define STR                2
#define BOOL               4

#define NOT_APPLICABLE    -1

/* 
 *  Datatype struct
*/
typedef struct
{
  int type;    // one of the above type codes
  union dataStor
  {
  int i;
  char* s;
  bool b;
  } data;
  int numParams; // NumParams and returnType only applicable
  int returnType; // if type == function
} TYPE_INFO;

typedef struct
{
  char* text; // the operator class
  char* op; // the exact operator
} OPERATOR_INFO;

stack<SYMBOL_TABLE> scopeStack;

int lineNum = 1; 

void printRule(const char *, const char *);

int yyerror(const char *s) {
  printf("Line %d: %s\n", lineNum, s);
}

extern "C" {
    int yyparse(void);
    int yylex(void);
    int yywrap() {return 1;}
}

void beginScope() // Call when let* or lambda is processed in mfpl.l.
{
  scopeStack.push(SYMBOL_TABLE());
  printf("\n___Entering new scope...\n\n");
}

void endScope() // Call when LET_EXPR or LAMBDA_EXPR is processed in mfpl.y.
{
  scopeStack.pop();
  printf("\n___Exiting scope...\n\n");
}

int findEntryInAnyScope(std::string theName)
{
  if(scopeStack.empty())
    return false;
  bool found = scopeStack.top().findEntry(theName);
  if(found)
    return true;
  else
  {// Check higher scopes
    SYMBOL_TABLE SymbolTable = scopeStack.top();
    scopeStack.pop();
    found = findEntryInAnyScope(theName);
    scopeStack.push(SymbolTable); // restore the stack
    return (found);
  }
}

TYPE_INFO CheckStringData(char* check)
{
  TYPE_INFO ret;
  ret.numParams = NOT_APPLICABLE;
  ret.returnType = NOT_APPLICABLE;
  
}
%}



/*
 *  union declaration 
*/
%union
{
  char* text;
  TYPE_INFO typeInfo;
  int list_length;
  OPERATOR_INFO opInfo;
};

/*
 *	Token declarations
*/
%token  T_LPAREN T_RPAREN 
%token  T_IF T_LETSTAR T_LAMBDA T_PRINT T_INPUT
%token  T_ADD  T_SUB  T_MULT  T_DIV
%token  T_LT T_GT T_LE T_GE T_EQ T_NE T_AND T_OR T_NOT	 
%token  T_INTCONST T_STRCONST T_T T_NIL T_IDENT T_UNKNOWN
%type<text> T_IDENT N_ARITH_OP N_REL_OP N_LOG_OP T_INPUT T_INTCONST T_STRCONST
%type<typeInfo> N_EXPR N_PARENTHESIZED_EXPR N_IF_EXPR N_ARITHLOGIC_EXPR
%type<typeInfo> N_LET_EXPR N_LAMBDA_EXPR N_PRINT_EXPR N_CONST N_INPUT_EXPR
%type<typeInfo> N_EXPR_LIST
%type<list_length> N_ID_LIST
%type<opInfo> N_BIN_OP

/*
 *	Starting point.
 */
%start  N_START

%%


%%

#include "lex.yy.c"
extern FILE *yyin;

void printRule(const char *lhs, const char *rhs) {
  printf("%s -> %s\n", lhs, rhs);
  return;
}

int main(int argc, char** argv) {
  if(argc < 2)
  {
    printf("You must specify a file in the command line!\n");
    exit(1);
  }
  do {
	yyparse();
  } while (!feof(yyin));

  return 0;
}
Last edited on
pr3dicine (4)
i have tried your code, i cant seem to get it to work for some odd reason. i was going to try and help, but i dont understand what is wrong. sorry about that.
Jakman217 (18)
One thing is that I took out the grammar and Lexemes to save space, the funny thing is My problem doesn't seem to be directly in my code. Mine freezes before it gets to the first lexeme in the input files. Doesn't even output, just freezes.
Last edited on
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