Bad file descriptor with coproc and pipe

[Michal Sojka]

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-pc-linux-gnu' 
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL 
-DHAVE_CONFIG_H   -I.  -I../bash -I../bash/include -I../bash/lib  
-D_FORTIFY_SOURCE=2 -g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat 
-Werror=format-security -Wall
uname output: Linux steelpick 3.12-1-amd64 #1 SMP Debian 3.12.6-2 (2013-12-29) 
x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 4.2
Patch Level: 45
Release Status: release

Description:
        The following commands fail:

            coproc while true; do echo $RANDOM; done
            cat <&${COPROC[0]} | cat

        The resulting error message is:

            bash: ${COPROC[0]}: Bad file descriptor

        The following commands (without the pipe) work as expected,
        i.e. the output of the coprocess is shown.

            coproc while true; do echo $RANDOM; done
            cat <&${COPROC[0]}

Thanks,
-Michal