Expect core dump

runnee.tcl

#!/bin/sh
# \
exec tclsh "$0" "$@"

set nb_iter 1000
set sleep   500

for {set i 0} {$i < $nb_iter} {incr i} {
    after $sleep
    puts $i
}

runner.tcl

#!/bin/sh
# \
exec tclsh "$0" "$@"

package require Expect

set nb_subproc 20
set sid_list [list]
set ::completed {}

for {set i 0} {$i < $nb_subproc} {incr i} {
    spawn [file normalize [file join [file dirname $::argv0] runnee.tcl]]
    lappend sid_list $spawn_id
    expect_background  {
        -i $spawn_id eof [list set ::completed $spawn_id]
    }
}

set aid [after 1200000 {set ::completed timeout}]
while {[llength $sid_list] > 0} {
    vwait ::completed
    if {"timeout" eq $::completed} {
        error timeout
    }
    set idx [lsearch $sid_list $::completed]
    if {-1 == $idx} {
        error "spawn_id $spwan_id not found in \"$sid_list\""
    }
    set sid_list [concat [lrange $sid_list 0 $idx-1] [lrange $sid_list $idx+1 end]]
}

exit 0

afaik, there is no guarantee that vwait returns for every set ::completed. Should be re-written lappend ::completed $spawn_id and wrap the removal in foreach sid $::completed {...} ; set ::completed {}.