K&R dcl program detects almost nothing

Question

I've been stuck with the dcl program from chapter 5.12 in K&R C. It is basically a program which accepts a C variable/function/table declaration and prints a description of it in English. It works for simple declarations such as int a but fails with more complicated ones. For example, when I enter int (*pf)() I get the output

error: expected name or (dcl)
Syntax error
:  int
error: expected name or (dcl)
:  function that returns pf

Below is the portion of the code related to the program. The getch() and ungetch() functions are in a separate file.

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include "getch.h"

#define MAXTOKEN 100

enum { NAME, PARENS, BRACKETS };

void dcl(void);
void dirdcl(void);
int gettoken(void);

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

int main(void)
{
    while (gettoken() != EOF) {
        strcpy(datatype, token);
        out[0] = '\0';
        dcl();
        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;

    if (tokentype == '(') {
        dcl();
        if (tokentype != ')')
            printf("error: missing )\n");
    } else if (tokentype == NAME)
        strcpy(name, token);
    else
        printf("error: expected name or (dcl)\n");
    while ((type=gettoken()) == PARENS || type == BRACKETS) {
        if (type == PARENS)
            strcat(out, " function that returns");
        else {
            strcat(out, " array");
            strcat(out, token);
            strcat(out, " of");
        }
    }
}

int gettoken(void)
{
    int c;
    char *p = token;

    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;
}

Could you please help me pinpoint the mistake?

You forgot to ask a question, but if you're wondering what's wrong with the program then the line return tokentype = ')'; in gettoken() looks wrong. It should probably be return tokentype = '(';, instead. There may be other issues. — John Bollinger
– John Bollinger, Commented Aug 5, 2021 at 18:00
Per request, mistake pinpointed: return tokentype = ')📍';. — Eric Postpischil
– Eric Postpischil, Commented Aug 5, 2021 at 18:07
@John Bollinger thank you. I added a question and from the beginning I found this part suspicious. The Greek print of the book has a ton of mistakes. — raf_135711
– raf_135711, Commented Aug 5, 2021 at 18:07

user2971293 · Accepted Answer · 2021-12-31 11:31:21Z

0

On p124 Brian and Dennis say "Since the programs are intended to be illustrative, not bullet-proof, there are significant restricts on dcl."

The final sentence in the paragraph has this version of the author's final cop-out: "These improvements are left as exercises."

This could be a good time to dust off yacc.

answered Dec 31, 2021 at 11:31

user2971293

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