Re: local root on linux 2.2.15

[pfaffben () MSU EDU (Ben Pfaff)]

Peter da Silva <peter () SCARYDEVIL ORG> writes:

> In article <87bt184i7z.fsf () arabella intern opera no> you write:
> >   cap_user_header_t header;
> >   cap_user_data_t data;
[...]
>          header = malloc(sizeof (cap_user_header_t) );
>          data = malloc(sizeof (cap_user_data_t) );

The comp.lang.c approved version of these statements would read:
        header = malloc (sizeof *header);
        data = malloc (sizeof *data);
given that the declarations were actually
        cap_user_header_t *header;
        cap_user_data_t *data;
or that cap_user_header_t and cap_user_data_t were typedefs of
pointer types.

There's a couple of reasons to do it this way:

        * If you ever change the type that `header' or `data'
          points to, for whatever reason, it's not necessary to
          change the malloc() call as well.  This is convenient
          and a handy safeguard against forgetting to change all
          your malloc() calls.

        * Taking the size of an object makes your sizeof call more
          similar to your declaration, which makes writing the
          statement less error-prone.

However, if the declarations were as above, with Peter's
statements, there is something wrong.  It is almost certainly a
mistake to use the same type for both the pointer and the
pointed-to object, as Peter's suggested code implies; the actual
equivalent of his code using sizeof on an object would be this:
        header = malloc (sizeof header);
        data = malloc (sizeof data);
Though I do not know what a cap_user_header_t or a
cap_user_data_t is, I can hardly believe that this is correct.

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