Thread: K&R Exercise 5-20 : bsearch Error when compiled

Problem

Expand dcl to handle declarations with function argument types, qualifiers like const, and so on.

Answer:
main.c

Code:

#include "extern.h"
#include <string.h>
#include <ctype.h>




enum { NAME, PARENS, BRACKETS};
enum {NO, YES};


void dcl (void);
void dirdcl(void);
void errmsg(char *);
int gettoken(void);


int tokentype;
char token[MAXTOKEN];
char name[MAXTOKEN];
char datatype[MAXTOKEN];
char out[1000];
int prevtoken;


int main()  /* convert declaration to words */
{
    while (gettoken() != EOF) { /* 1st token on line */
         strcpy(datatype, token);   /* is the datatype */
         out[0] = '\0';
         dcl();         /* parse rest of line */
         if (tokentype != '\n')
            printf("syntax error\n");
         printf("%s:  %s %s\n", name, out, datatype);
    }
    return 0;
}


void dcl (void)
{
    int ns;
    for(ns = 0; gettoken() == '*'; )
        ns++;
    dirdcl();
    while(ns-- > 0)
        strcat(out, " pointer to");
}


void dirdcl(void)
{
    int type;
    void parmdcl(void);
    if(tokentype == '(') {
        dcl();
        if(tokentype != ')')
            errmsg("error: missing )\n");
    } else if (tokentype == NAME) {
        if(name[0] == '\0')
            strcpy(name, token);
    } else
        prevtoken = YES;
    while((type = gettoken()) == PARENS || type == BRACKETS || type == '(')
        if(type == PARENS)
            strcat(out, "function returning");
        else if (type == '(') {
            strcat(out, " function expecting");
            parmdcl();
            strcat(out, " and returning");
        } else {
            strcat(out, " array");
            strcat(out, token);
            strcat(out, " of");
        }
}


void errmsg(char *msg)
{
    printf("%s",msg);
    prevtoken = YES;
}

parmdcl.c

Code:

#include "extern.h"
#include <string.h>
#include <stdlib.h>
#include <ctype.h>


enum { NAME, PARENS, BRACKETS};
enum { NO, YES};


void dcl(void);
void errmsg(char *);
void dclspec(void);
int typespec(void);
int typequal(void);
int compare(char **, char **);
int gettoken(void);


int tokentype;
char token[MAXTOKEN];
char name[MAXTOKEN];
char datatype[MAXTOKEN];
char out[MAXTOKEN];
int prevtoken;


void parmdcl(void)
{
        do {
            dclspec();
        } while(tokentype == ',');
        if(tokentype != ')')
            errmsg("missing ) in parameter declaration\n");
}


void dclspec (void)
{
    char temp[MAXTOKEN];
    temp[0] = '\0';
    gettoken();
    do {
        if (tokentype != NAME) {
            prevtoken = YES;
            dcl();
        } else if (typespec() == YES) {
                strcat(temp, " ");
                strcat(temp, token);
                gettoken();
        } else if(typequal() == YES) {
                strcat(temp, " ");
                strcat(temp, token);
                gettoken();
        } else
            errmsg("unknown type in parameter list \n");
    } while (tokentype != ',' && tokentype != ')');
    strcat(out, temp);
    if(tokentype == ',')
        strcat(out, ",");
}


int typespec(void)
{
    static char *types[] = {
        "char",
        "int",
        "void"
    };
    char *pt = token;
    
    if (bsearch(&pt, types, sizeof(types)/sizeof(char *), sizeof(char *), compare)==NULL)
        return NO;
    else
        return YES;
}


int typequal(void)
{
    static char *typeq[] = {
            "const",
            "volatile"
    };
    char *pt = token;
    
    if(bsearch(&pt, typeq, sizeof(typeq)/sizeof(char *), sizeof(char *), compare) == NULL)
        return NO;
    else
        return YES;
    
}


int compare(char **s, char **t)
{
    return strcmp(*s, *t);
}

gettoken.c

Code:

#include "extern.h"
#include <ctype.h>
#include <string.h>


enum {NAME, PARENS, BRACKETS};
enum {NO, YES};


int tokentype;
char token[MAXTOKEN];
int prevtoken = NO;


int gettoken(void)
{
    int c, getch(void);
    void ungetch(int);
    char *p = token;
    
    if (prevtoken == YES) {
        prevtoken = NO;
        return tokentype;
    }
    while((c = getch()) == ' ' || c == '\t')
        ;
    if (c == '(') {
        if ((c = getch()) == ')') {
            strcpy (token, "()");
            return tokentype = PARENS;
        } else {
            ungetch(c);
            return tokentype = '(';
        }
    } else if (c == '[') {
        for(*p++ = c; (*p++ = getch()) != ']'; )
            ;
        *p = '\0';
        return tokentype = BRACKETS;
    } else if (isalpha(c)) {
        for(*p++ = c; isalnum(c = getch()); )
            *p++ = c;
        *p = '\0';
        ungetch(c);
        return tokentype = NAME;
    } else
        return tokentype = c;
}


#define BUFSIZE 100
 
char  buf[BUFSIZE]; /* buffer for ungetch */
int   bufp = 0;     /* next free position in buf */
 
int getch(void)     /* get a (possibly pushed back) character */
{
    return (bufp > 0)  ?  buf[--bufp]  :  getchar();
}
 
void ungetch(int c) /* pretend to push character back on input */
{
    if (bufp >= BUFSIZE) 
        printf("ungetch:  too many characters\n");
    else 
        buf[bufp++] = c;
}

extern.h

Code:

#include <stdio.h>
extern int tokentype;
extern char token[];
extern char name[];
extern char datatype[];
extern char out[];
extern int prevtoken;


#define MAXTOKEN 100

gcc main.c parmdcl.c gettoken.c -Wall -Werror -pedantic -g -o dcl.exe
Error: passing argument 5 of 'bsearch' from incompatible pointer type [-Werror]

So i think the 5th argument of bsearch doesn't seem to accept double pointers. The function compare()'s parameter have two double pointers because it will receive string arguments for the bsearch (from <stdlib.h>) to compare them if they are in the static char arrays, *typeq[] and *types[].

The error lies in the functions typespec() and typequal() in the parmdcl.c sourcefile. Anyone know how to make this work?