Version 4 of atProcExit

Updated 2008-08-26 12:24:39 by mig

[TODO: describe (only NRE-wiki page of relevance appears to be [L1 ]); rename the command to something more tclish?] Consequence of NRE.

Lars H: A thought: how is this different from what can be had through the age-old technique of creating a dummy local variable and putting an unset trace on it? Basic implementation:

 proc atProcExit {script} {
    upvar 1 atProcExitScripts arr
    set arr($script) {}
    trace add variable arr($script) unset "$script\n\#"
 }

MS 2008-08-26 First please note that this is mostly exploiting the infrastructure of tailcall for a different and possibly interestuig purpose, but is definitely the least thought-out of the new unsupported commands. It might not be more than a "tech show-off" for NRE.

Now to the actual question: some of the differences are:

  • no need to find a variable name that is guaranteed not to be used, even in procs that may create and manipulate variables with names coming from the user
  • the state of the interp when the script runs: with the var traces, the proc's internal structures are still occupying the Tcl stack, and some of the code is still using the C stack. These run when everything is really gone, just like tailcall would.
  • well defined execution sequence (LIFO), which your construct does not guarantee (it is possible to have this feature with variable traces by putting the scripts in a list and running them in order within a [catch])
Category Command