Global variables

This article is about planned development or proposed functionality. Comments welcome.

We would like to get rid of the current use of global variables in ASCEND, so that we can start to think about using ASCEND in multithreaded and/or embedded ways. This page will report any cases of global variables that we have found, and perhaps some discussion about how we can best eliminate them. Not all cases will be the same.

Ways for removing global variables

A number of options exist:

• keeping them. This is appropriate in a very limited set of situations, such as for data that has been loaded from a configuration file when the program started.
• groupin them into a top-level data structure. We imagine structures like "library", "simulation" and "system" could be created that could hold most global variables.
• passing them. Where global variables have been used as a convenience to avoid having to expand function parameter lists, we can just change to passing them as parameters.
• converting them to #defines. May be appropriate for certain constants.
• converting them to thread-local variables (may need to assess implication for embedded applications)
• adding mutex constraints (so that they can only be accessed once at a time)
• migrating them to another code layer, eg into the GUI (this has already been done in some cases)

Global variables in libascend.so

The main place where global variables are a problem for ASCEND is in libascend, our core library include the ASCEND parser/compiler and evaluation routines, but hopefully excluding the solvers.

Below is a list of globals generated using GNU nm.

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a4c, abap, abc, abnf, actionscript, ada, agda, alan, algol, ampl, amtrix, applescript, arc, arm, as400cl, ascend, asciidoc, asp, aspect, assembler, ats, autohotkey, autoit, avenue, awk, ballerina, bat, bbcode, bcpl, bibtex, biferno, bison, blitzbasic, bms, bnf, boo, c, carbon, ceylon, charmm, chill, chpl, clean, clearbasic, clipper, clojure, clp, cmake, cobol, coffeescript, coldfusion, conf, cpp2, critic, crk, crystal, cs_block_regex, csharp, css, d, dart, delphi, diff, dockerfile, dts, dylan, ebnf, ebnf2, eiffel, elixir, elm, email, erb, erlang, euphoria, exapunks, excel, express, factor, fame, fasm, felix, fish, fortran77, fortran90, frink, fsharp, fstab, fx, gambas, gdb, gdscript, go, graphviz, haml, hare, haskell, haxe, hcl, html, httpd, hugo, icon, idl, idlang, inc_luatex, informix, ini, innosetup, interlis, io, jam, jasmin, java, javascript, js_regex, json, jsp, jsx, julia, kotlin, ldif, less, lhs, lilypond, limbo, lindenscript, lisp, logtalk, lotos, lotus, lua, luban, makefile, maple, markdown, matlab, maya, mercury, meson, miranda, mod2, mod3, modelica, moon, ms, msl, mssql, mxml, n3, nasal, nbc, nemerle, netrexx, nginx, nice, nim, nix, nsis, nxc, oberon, objc, ocaml, octave, oorexx, org, os, oz, paradox, pas, pdf, perl, php, pike, pl1, plperl, plpython, pltcl, po, polygen, pony, pov, powershell, pro, progress, ps, psl, pure, purebasic, purescript, pyrex, python, q, qmake, qml, qu, r, rebol, rego, rexx, rnc, rpg, rpl, rst, ruby, rust, s, sam, sas, scad, scala, scilab, scss, shellscript, slim, small, smalltalk, sml, snmp, snobol, solidity, spec, spn, sql, squirrel, styl, svg, swift, sybase, tcl, tcsh, terraform, tex, toml, tsql, tsx, ttcn3, txt, typescript, upc, vala, vb, verilog, vhd, vimscript, vue, wat, whiley, wren, xml, xpp, yaiff, yaml, yaml_ansible, yang, zig, znn

Static variables

Another place where quasi-global variables can occur is as static variables within functions. It needs to be assessed whether the above listing includes those types of variables.