BUG #4089: When available disk space is low pg_stop_backup() fails, as do subsequent recovery attempts.

The following bug has been logged online:

Bug reference: 4089
Logged by: John Smith
Email address: sodgodofall(at)gmail(dot)com
PostgreSQL version: 8.3.0
Operating system: Linux 2.6.20-gentoo-r8
Description: When available disk space is low pg_stop_backup() fails,
as do subsequent recovery attempts.
Details:

Steps to reproduce:
-- start with a running PG instance with WAL archiving enabled
-- select pg_start_backup('test');
-- Fill up the disk on which the data directory is present
-- select pg_stop_backup();
-- fails with: ERROR: could not write file
"pg_xlog/000000010000000000000000.004989E8.backup": No space left on device
-- at this point there is a 0-byte file
pg_xlog/000000010000000000000000.004989E8.backup present on disk
-- stop and start PG
-- recovery fails with: FATAL: invalid data in file
"000000010000000000000000.004989E8.backup"
-- NOTE: At this point removing 000000010000000000000000.004989E8.backup
allows PG to start successfully