Question

Now here’s something interesting. When I have more than one thread in Tcl invoking package require Expect, I get a seg fault.

e.g.

package require Threads  
package require Expect

set t [thread::create]

thread::send {package require Expect}

puts "blarg! Damned thing crashes before I get here"

This is not a good time. Any thoughts?

Answer 1

Expect and Threads don’t go together too well. Its the complexity you get from fork() + threads that can bite a lot there and lead to deadlocks and all kinds of uglyness. Usually not a good idea to combine the two.

If you really need Expect and the added concurrency a multi process approach with on multi threaded driver program and one single threaded expect process might work better. If you used tcllibs comm package the api’s for sending commands are not that much different either (you mostly miss the tsv and tpool stuff if you used comm).

But it shouldn’t segfault for sure. Which Expect/Threads/Tcl core combination did you use (e.g. ActiveStates ActiveTcl bundle or some self compiled stuff on an unusual platform?)