Bug in libpq large-object interface

Hi PostgreSQL people in general and Tatsuo in particular,

I'm using V 7.0 on a Linux machine and I believe I have found a bug in the
large object interface provided by libpq. The code below will reproduce it, I
hope. Basically it creates a large object, writes six 'a' characters to it,
then closes it. Then, in another transaction, it opens the object, seeks to
position 1 from the start, writes a 'b', then seeks to position 3 from the
start and writes another 'b'. Then it closes the object and COMMITs the
transaction. Finally, in a further separate transaction, it calls lo_export
to write out the resulting object to a file testloseek.c.lobj I find this
file, instead of containing the string 'ababaa' as expected, contains
'^@b^@baa' where ^@ is ASCII NUL.

Compile with something like

gcc -o testloseek testloseek.c -lpq

The program sets the PQtrace to STDOUT and writes messages to STDERR, so run
it with STDOUT redirected to a log file.

This is a C version of a basic regression test of guile-pg, my Guile language
bindings for libpq. You may recall I reported a similar bug a year or so ago,
and I believed it was then fixed by Tatsuo, after a couple of iterations. I'm
sorry to be the bearer of bad news ...

Please reply to me directly since I'm not on the list.

Thanks
Ian
--
Ian Grant, Computer Lab., New Museums Site, Pembroke Street, Cambridge
Phone: +44 1223 334420 Personal e-mail: iang at pobox dot com