Thread: array on heap, pointers to and from functions, Bus error: 10

Hello,

Any ideas what's wrong with this?:

Code:

typedef unsigned char * test;

void init_test(test *t);
void insert(test *t);
void free_test(test *t);


int main() {
    test t;


    init_test(&t);
    insert(&t);
    
    printf("%d\n", t[0]);

    free_test(&t);
    
    return 0;
}




void init_test(test *t) {
    *t = malloc(100 * sizeof(*t));
}


void insert(test *t) {
    *t[0] = 200;
    *t[1] = 201;
    *t[2] = 202;
    *t[3] = 203;
}


void free_test(test *t) {
    free(*t);
    *t = NULL;
}

I know you're not really supposed to put *'s in typedefs but I really want to just for this example.

The bus error is happening, I think, in the insert function.

Any suggestions much appreciated.

According to this helpful page, array subscripting is of higher precedence than dereference. What this means is that in insert() you try to access 4 different array pointers while you have only one.

Your compiler should have warned you about this error if you had warnings enabled.
( Or rather, it would warn you about trying to assign an integer value to a pointer )

My immediate first thought from your reply was

Code:

void insert(test *t) {
    (*t)[0] = 200;
    (*t)[1] = 201;
    (*t)[2] = 202;
    (*t)[3] = 203;
}

That seems to have done it

Thanks.

edit: the compiler did not warn me. I was compiling with gcc -Wall test.c -o test , -Wall is warning all on right?
gcc version 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.9.00)