restores unit tracking in the plugin facility #1548
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After we switched to OCaml 4.08 and above, we trashed custom unit tracking from our plugin system and started to rely on the Dynlink facility, provided by OCaml, that offers precise unit tracking. However, Dynlink is not allowed inside OCaml Toplevel, which wasn't noticed, because it wasn't properly initialized (though apparently it worked fine for our needs). But after 4.12 (see ocaml/ocaml#9790) it was properly initialized so we started to get "The dynlink.cma library cannot be used inside the OCaml toplevel" messages when trying to use `baptop` or `bap.top`. A quick-fix (BinaryAnalysisPlatform#1541) did only worse as it disabled any unit tracking and enabled double-loading of plugins and libraries (which is perfectly allowed in OCaml toplevel and is not a bug, as it was in regular OCaml runtime). Of course, double-loading could crash bap as many of bap libraries have their own state, which got reset after reloading. This PR restores the old findlib-based unit tracker. This tracker is not precise and may still miss loaded units. For example, if you load bap manually and the do `#require "bap.top"` it will reload bap (which should be a problem, but who knows). With that said, we had used this tracker for many years, up until BAP 2.4.0, so I do have some trust in it. Also, I don't want to invest more time in this issue as we are in the process of switching to dune and thhe dune plugin system (that has its own unit tracking system, which is precise). To be honest, dune plugins also do not work in toplevel right now, but this is a developing story (ocaml/dune#6081) and I hope that eventually we will have it working.
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After we switched to OCaml 4.08 and above, we trashed custom unit tracking from our plugin system and started to rely on the Dynlink facility, provided by OCaml, that offers precise unit tracking. However, Dynlink is not allowed inside OCaml Toplevel, which wasn't noticed, because it wasn't properly initialized (though apparently, it worked fine for our needs). But after 4.12 (see ocaml/ocaml#9790) it was properly initialized so we started to get "The dynlink.cma library cannot be used inside the OCaml toplevel" messages when trying to use
baptoporbap.top. A quick-fix (#1541) did only worse as it disabled any unit tracking and enabled double-loading of plugins and libraries (which is perfectly allowed in OCaml toplevel and is not a bug, as it was in regular OCaml runtime). Of course, double-loading could crash bap as many of bap libraries have their own state, which got reset after reloading.This PR restores the old findlib-based unit tracker. This tracker is not precise and may still miss loaded units. For example, if you load bap manually and then do
#require "bap.top"it will reload bap (which should not be a problem, but who knows). With that said, we had used this tracker for many years, up until BAP 2.4.0, so I do have some trust in it. Also, I don't want to invest more time in this issue as we are in the process of switching to dune and the dune plugin system (which has its own unit tracking system that is precise). To be honest, dune plugins also do not work in toplevel right now, but this is a developing story (ocaml/dune#6081) and I hope that eventually, we will have it working.