BUG #5631: psql dumps core during command editing

The following bug has been logged online:

Bug reference:      5631
Logged by:          David Kensiski
Email address:      David@Schoolloop.com
PostgreSQL version: 8.4
Operating system:   Solaris 10
Description:        psql dumps core during command editing
Details:

The psql binary (64-bit from binary install) dumps core when I attempt to
edit the input line after a few characters are entered:

tombu@i2:~$ psql homerdb
psql (8.4.4)
Type "help" for help.

homerdb=# abcde(Ctrl-A)Segmentation Fault (core dumped)

Note that "abcd(Ctrl-A)" doesn't result in a Seg Fault, though
"abcde(Ctrl-A)" does.

Here's the tail end of a truss of the psql process:

read(0, " d", 1)                                = 1
write(1, " d", 1)                               = 1
read(0, " e", 1)                                = 1
write(1, " e", 1)                               = 1
read(0, "01", 1)                                = 1
    Incurred fault #6, FLTBOUNDS  %pc = 0xFFFFFD7FFEF087C2
      siginfo: SIGSEGV SEGV_MAPERR addr=0xFFFFFFFFFEF2D500
    Received signal #11, SIGSEGV [default]
      siginfo: SIGSEGV SEGV_MAPERR addr=0xFFFFFFFFFEF2D500

Alas, I'd give you a backtrace, but I'm running the 64-bit binary and only
have a 32-bit gdb.