Incompatible Pointer Type?

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I am writing code to a set of methods for a binary tree and have received this compilation error:

pfbst.c: In function ‘main’:
pfbst.c:65:13: warning: passing argument 2 of ‘bst_char_iterate’ from incompatible pointer type [enabled by default]
bst_char_iterate(t,print_char);
^
In file included from pfbst.c:6: 0:
pfbst_char.h:26:6: note: expected ‘char (*)(char)’ but argument is of type ‘void (*)(char)’
int bst_char_iterate(bst_char *t, char (*fun)(char item));
^

Here's the code:

C

int bst_iterate(struct node *p, char (*fun)(char item)) {
    if (p!=NULL) {
       p->item = fun(p->item);
       bst_iterate(p->left,fun);
       bst_iterate(p->right,fun);
    } else {
       return 0;
    }
}

int bst_char_iterate(bst_char *t, char (*fun)(char item)) {
    assert(t!=NULL);
    bst_iterate(t->root,fun);
}

Posted 13-Jan-14 9:42am

MikeBah

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Comments

CPallini 13-Jan-14 15:53pm

The error is in your main function, for better help, you should post the relevant code here.

CHill60 13-Jan-14 15:56pm

Beat me to it!

1 solution

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Vedat Ozan Oner · Accepted Answer · 2014-01-13T10:40:00

Solution 1

C++

bst_char_iterate(t,print_char);

part causes the error. Your print_char function signature differs from the expected one as in the error.

Quote:
pfbst_char.h:26:6: note: expected ‘char (*)(char)’ but argument is of type ‘void (*)(char)’

If you change print_char's return type to char and return a char in the function, the compiler will stop complaining :)

C++

char print_char(char c) {
 return 0;
}

Posted 13-Jan-14 10:40am

Vedat Ozan Oner

Comments

Stefan_Lang 14-Jan-14 10:47am

Good work - looks like a perfect fix for me, constructed from only the error message without the code! My 5!

On a sidenote: this should be a lesson to the poster: just reading the error message reveals the problem and the fix!