Separating stdout and stderr

Hi,

We suspect that the non-ordered nature of stdout vs stderr is causing
random problems in our GCC validations.

I wanted to experiment with forcing separation between stdout and
stderr, then concatenating them, but so far I haven't been able to
twist dejagnu to do so.


I wanted to make use of a function like "invoke" as defined in
http://wiki.tcl.tk/1241. I tried to call "invoke" instead of "spawn"
but it seems that $spawn_id is not set by "open", but this variable is
needed by dejagnu (local_exec in remote.exp).


Then, I thought I could force output redirection, hence using an
existing code-path in dejagnu (still in local_exec in remote.exp). To
this end, at the beginning of local_exec, if $outp is empty, I force
it to, say /tmp/foo.pid and set a flag to remember this later.
In the code handling the redirection, I replaced
set outp "> $outp"
with
set outp "> $outpf 2> ${outpf}.err"

Now before resuming the normal code-path, I need to execute "cat
$outpf ${outpf}.err" (if the flag I mentioned above is set):
set result [catch {open "| cat $outpf ${outpf}.err" "w"} id]

But I keep having errors in the expect statement a few lines later:
ERROR: bad spawn_id (process died earlier?)
    while executing
"expect {
        -i $spawn_id -timeout $timeout -re ".+" {
            append output $expect_out(buffer)
            if { [string length $output] < 512000 } {
                exp_contin..."
    (procedure "local_exec" line 117)

I hoped that the statement:
set result [catch "spawn -ignore SIGHUP -leaveopen $id" result2]

would setup $spawn_id and help building $output

I'm surely missing something obvious, but I'm not very fluent in tcl :(

I'd like to make this "work" and experiment with it to check if it
would make our validations more reliable.

Thanks,

Christophe.