[Xsb-development] Global variables in XSB

[Terrance S. <ts...@cs...>]

All:

      One of the tasks necessary in making the MT engine stable enough
      for release is to get a handle on global variables.

      In the course of developing the MT engine, Rui has identified
      most of the global variables in the system and ensured that many
      of these variables are put into thread-specific data structures
      when compiling with multi-threading, and that many of the rest
      are used only in procedures that are controlled by mutexes.

      I took the latest version of the MT engine, loaded it in gdb,
      and ran the "info variables" command.  which shows all non-local
      variables, both static and non-static.  There are about 260 of
      these left.  Some of these are innocuous; many are time-bombs.
      I'd like to propose the following method to deal with global
      variables in the system.

      1) ifdef out any variables that are not intended for use in the
         MT engine (as we have been doing)

      2) For those variables that are intended to constants, append
         _glc to their name (for global constant)

      3) For those global variables that are not constants, but are to
         be included in the MT configuration, append _gl to their
         names, indicating that they have been accounted for in some
         way.

      4) Once we've accounted for all global variables, we make it
         part of our check-in procedure that we don't include any more
         unintended global variabls.

I'm willing to take the lead on this if others agree, (and if nobody
has a better idea on how to deal with the issue).  In the absence of
comments, I'll start on it some time next week.

Terry