byacc - Exception trapped

byacc - Exception trapped

[Earnie Boyd]

[-- Attachment #1: Type: text/plain, Size: 784 bytes --]

This should be simple:

I wanted to learn lex & yacc.  So I bought the O'Reilly & Associates 
book.  I begin compiling and linking the examples.  Things are looking 
good and working fine; until, I get to the yacc section in chapter 1.

I have the lex examples coded from Example 1.6 and the yacc examples 
coded from Example 1.7 and 1.8.  I then do:

    flex ch1-05.flex
    byacc ch1-05.byacc
    gcc -c lex.yy.c y.tab.c
    gcc -o ch1-05 lex.yy.o y.tab.o -lfl

Now here is where the problem starts:
I execute ch1-05 and get the attached dump. 8^(

I've also attached the flex and byacc source files.


Does anyone have a solution?

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ch1_05_error
ch1_05_byacc
ch1_05_flex

[-- Attachment #2: ch1_05_byacc --]
[-- Type: text/x-c, Size: 522 bytes --]

%{
/*
 * Example 1-7: Simple yacc sentence parser ch1-05.byacc
 *
 * A lexer for the basic grammer to use for recognizing English sentences.
 */
#include <stdio.h>
%}

%token NOUN PRONOUN VERB ADVERB ADJECTIVE PREPOSITION CONJUNCTION

%%

sentence: subject VERB object { printf("Sentence is valid.\n"); }
    ;

subject:    NOUN
    |       PRONOUN
    ;

object:     NOUN
    ;

%%

extern FILE *yyin;

main()
{
    while(!feof(yyin)) {
        yyparse();
    }
}

yyerror(s)
char *s;
{
    fprintf(stderr, "%s\n", s);
}

[-- Attachment #3: ch1_05_error --]
[-- Type: text/plain, Size: 1558 bytes --]

(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) In cygwin_except_handler
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) Exception trapped!
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) exception C0000005 at 402C75
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) exception: ax 0 bx 0 cx 10047814 dx 0
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) exception: si 5 di 1000B8B3 bp 240F01C sp 240F01C
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) exception is: STATUS_ACCESS_VIOLATION
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) Stack trace:
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) frame 0: sp = 0x240EE58, pc = 0x1000CEC2
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) frame 1: sp = 0x240EE74, pc = 0x77FA9182
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) frame 2: sp = 0x240EE98, pc = 0x77FA037B
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) frame 3: sp = 0x240EF1C, pc = 0x77F903C2
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) frame 4: sp = 0x240F01C, pc = 0x1000C102
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) frame 5: sp = 0x240FFC4, pc = 0x1000C113
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) frame 6: sp = 0x240FFD0, pc = 0x4032F1
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) frame 7: sp = 0x240FFE0, pc = 0x40103B
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) frame 8: sp = 0x240FFF0, pc = 0x0
(c:\users\bcoeeb0\My Projects\learn\lex\ch1-05.exe 4057) End of stack trace

[-- Attachment #4: ch1_05_flex --]
[-- Type: text/x-c, Size: 2854 bytes --]

%{
/*
 * Example 1-6: Lexer to be called from the parser ch1-05.flex
 *
 * We now build a lexical analyzer to be used by a higher-level parser.
 *
 */

#include "y.tab.h"      /* token codes from the parser */

#define LOOKUP 0        /* default - not a defined word type. */

int state;
int add_word(int typ, char *word);
int lookup_word(char *word);

%}

%%

    /*
     * end of line, return to default state 
     */

\n      { 
            state = LOOKUP; 
        }

    /*
     * end of sentence
     */
     
\.\n    {   state = LOOKUP; 
            return 0; 
        }

    /* whenever a line starts with a reserved part of speech name
     * start defining words of that type.
     */

^verb   { state = VERB; }
^adj    { state = ADJECTIVE;  }
^adv    { state = ADVERB;  }
^noun   { state = NOUN; }
^prep   { state = PREPOSITION; }
^pron   { state = PRONOUN; }
^conj   { state = CONJUNCTION; }

    /*
     * a normal word, define it or look it up
     */
[A-Za-z]+  {
            if (state != LOOKUP) {
                add_word(state, yytext);    /* define the current word */
            } else {
                switch (lookup_word(yytext)) {
                    case VERB:          return(VERB);
                    case ADJECTIVE:     return(ADJECTIVE);
                    case ADVERB:        return(ADVERB);
                    case NOUN:          return(NOUN);
                    case PREPOSITION:   return(PREPOSITION);
                    case PRONOUN:       return(PRONOUN);
                    case CONJUNCTION:   return(CONJUNCTION);
                    default:    printf("%s: don't recognize\n", yytext);
                    /* don't return, just ignore it */
                }
            }
           }

.   /* ignore anything else */ ;

%%

/*
 * define a linked list of words and types
 */


struct word {
    char *word_name;
    int word_type;
    struct word *next;
};

struct word *word_list; /* first element in word list */

extern void *malloc();

int
add_word(int type, char *word)
{
    struct word *wp;

    if (lookup_word(word) != LOOKUP) {
        printf("!!! warning: word %s already defined \n", word);
        return 0;
    }

    /* word not there allocate a new entry and link it on the list */

    wp = (struct word *) malloc(sizeof(struct word));

    wp->next = word_list;

    /* have to copy the word itself as well */

    wp->word_name = (char *) malloc(strlen(word)+1);
    strcpy(wp->word_name, word);
    wp->word_type = type;
    word_list = wp;
    return 1;                   /* it worked */
}

int
lookup_word(char *word)
{
    struct word *wp = word_list;

    /* search down the list looking for the word */
    for (; wp; wp = wp->next) {
        if (strcmp(wp->word_name, word) == 0)
            return wp->word_type
        ;   /* endif */
    }

    return LOOKUP; /* not found */
}