Returning a pointer to a struct

Question

I came across a example returning a struct in 'C Programming Language' by Kernighan & Ritchie.

/* binsearch: find word in tab[0]...tab[n-1] */
struct key *binsearch(char *word, struct key *tab, int n)
{
    int cond;
    struct key *low = &tab[0];
    struct key *high = &tab[n];
    struct key *mid;

    while (low < high) {
        mid = low + (high-low) / 2;
        if ((cond = strcmp(word, mid->word)) < 0)
            high = mid;
        else if (cond > 0)
            low = mid + 1;
        else
            return mid;
    }

    return NULL;
}

It seems that the function is returning a pointer to a local var in the function; wouldn't this be a case of returning a dangling pointer?

score 7 · Accepted Answer · answered Jan 08 '12 at 05:52

No, this function does not return a pointer to a local variable. There are, in fact, no local variables of type struct key in this function at all.

This function returns a pointer to one of the struct key elements from the tab array provided to this function by its caller.

score 1 · Answer 2 · answered Jan 08 '12 at 05:51

1

Not in this case, since only the pointers are local, not the structs themselves, as they are passed from outside in the argument tab.

answered Jan 08 '12 at 05:51

MByD

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score 1 · Answer 3 · answered Jan 08 '12 at 06:00

1

I think you are referring to the binsearch code mentioned in page #137. To get better understanding of the code, you need to read the explanation given in page #138.

@K&R

@The C Programming Language

@Second Edition

answered Jan 08 '12 at 06:00

Sangeeth Saravanaraj

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Returning a pointer to a struct

3 Answers3