'wait $COPROC_PID' doesn't wait

[Davide Baldini]

Configuration Information [Manually filled]:
Machine: i686
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: //
uname output: Linux debianBunker 2.6.26-pentium4 #11 Fri Jul 20 10:03:38 CEST 
2012 i686 GNU/Linux
Machine Type: i486-pc-linux-gnu

Bash Version: 4.2.0(5)-release (i686-pc-linux-gnu)

Description:
        The following test script floods the console repeating lines similar to:
            ./debug.sh: line 7: warning: execute_coproc: coproc [8740:COPROC] 
still exists
            ./debug.sh: line 7: warning: execute_coproc: coproc [8741:COPROC] 
still exists

        I'd expect 'wait $COPROC_PID` to quietly wait without warnings.
        This problem doesn't occur with bash 4.1.5(1)-release
        (i486-pc-linux-gnu).

        I don't remember the used compilation CFLAGS. I can recompile if these
        are necessary.

Repeat-By:
        #!/bin/bash
        f() { :; }

        while :; do
            coproc f par1
            wait $COPROC_PID
        done