debug problem --> chapter 5.6 K&R

Code:

---

#include <stdio.h>
#include <string.h>
#define MAXLINES 5000 /* max #lines to be sorted */
char *lineptr[MAXLINES]; /* pointers to text lines */
int readlines(char *lineptr[], int nlines);
void writelines(char *lineptr[], int nlines);
void qsort(char *lineptr[], int left, int right);
/* sort input lines */
main()
{
        int nlines; /* number of input lines read */
        if ((nlines = readlines(lineptr, MAXLINES)) >= 0) {
                qsort(lineptr, 0, nlines-1);
                writelines(lineptr, nlines);
                return 0;
        } else {
                printf("error: input too big to sort\n");
                return 1;
        }
}
#define MAXLEN 1000 /* max length of any input line */
int getline(char *, int);
char *alloc(int);
/* readlines: read input lines */
int readlines(char *lineptr[], int maxlines)
{
        int len, nlines;
        char *p, line[MAXLEN];
        nlines = 0;
        while ((len = getline(line, MAXLEN)) > 0)
                if (nlines >= maxlines || (p = alloc(len)) == NULL)
                        return -1;
                else {
                        line[len-1] = '\0'; /* delete newline */
                        strcpy(p, line);
                        lineptr[nlines++] = p;
                }
        return nlines;
}
/* writelines: write output lines */
void writelines(char *lineptr[], int nlines)
{
        int i;
        for (i = 0; i < nlines; i++)
                printf("%s\n", lineptr[i]);
}

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Could you please help me out why I cannot debug? How to do so...

I get these two errors:
"_alloc", referenced from:
"_getline", referenced from:

Looking forward to your answers!

As far as I can tell, it looks like you don't have alloc() or getline() anywhere in your source. But you call these functions, so they need to be included as a preprocessor directive or directly in the source.

done! thanks