Memory leak when catting(/sedding/...) large binary files with backticks

[benj]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' 
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-redhat-linux-gnu' 
-DCONF_VENDOR='redhat' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL 
-DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib  -D_GNU_SOURCE  -O2 -g -pipe 
-Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector 
--param=ssp-buffer-size=4 -m64 -mtune=generic
uname output: Linux pmpc983.npm.ac.uk 2.6.24.4-64.fc8 #1 SMP Sat Mar 29 
09:15:49 EDT 2008 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-redhat-linux-gnu

Bash Version: 3.2
Patch Level: 33
Release Status: release

Description:
        Using echo `cat ...` on a large binary file causes lots of memory to be 
used (fine), but if you ctrl-c while it's running
        it doesn't die properly and doesn't return used memory when finished. 
Originally found by screwing up a sed command (can
        also reproduce bug using sed rather than cat) while trying to rename a 
group of files.

Repeat-By:
        Every time
        1. Find large binary data file for test (mine is ~3.2GB)
        2. echo `cat filename` 
        3. Ctrl-C previous command while running (doesn't terminate)
        4. When step 2 eventually returns it does not release memory