Re: pg_dump's checkSeek() seems inadequate

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Sun, Jun 27, 2010 at 1:42 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> If I change the test to be
>> fseeko(fp, 0, SEEK_SET)
>> then it does the right thing.

> Well, I guess it depends on what you think the chances are that the
> revised test will fail on some other obscure platform.

To believe that, you'd have to believe that fseeko(fp, 0, SEEK_SET)
will fail but fseeko(fp, something-not-zero, SEEK_SET) will succeed.

A somewhat more plausible scenario is that somebody might hope that
they could do something like this:

echo 'some custom header' >pg.dump
pg_dump -Fc >>pg.dump

I believe that (at least on most Unixen) doing fseeko(fp, 0, SEEK_SET)
would result in overwriting the custom header, where it would not have
been overwritten before. However the usefulness of the above is at
best far-fetched; and I'm not very sure that it works today anyway,
since pg_dump/pg_restore seem to assume that manual byte counting should
match the results of ftell().

regards, tom lane