[WIP] [lldb] [debugger] miscellaneous issues

[timotheecour]

(closing until I clean this up)

easy

• nim --debugger:native --lldb[:path/to/lldb] file.nim arg1 arg2 should compile and run via lldb -- app arg1 arg2 (likewise: --gdb[path/to/gdb] would compile and run via gdb specific syntax, ie: gdb --args app arg1 arg2

major

• lldb should have Nim added as a language plugin; it should have bulk of it's logic written in Nim and be dlopen'd in lldb; see also [2]
• calling code (eg via p mynimfun) via unmangled names should be supported
• b mynimfun doesn't work
  WORKAROUND: rbreak \bmynimfun_ (ie, regex) ; or b mynimfun[TAB] for auto-completion
• stacktraces should show demangled names instead of mangled ones:
  * frame #0: 0x0000000100000dd8 app fun2_ALFlENhZsqTbOkwPqw67Tg_2 + 40 at ...
• sample code showing how to write lldb plugins for nim (maybe wrapping around lldb's python plugin api)
• lldb nim plugin should pretty-print variables correctly, eg:

(const (anonymous struct)) TM_p8kKrP3l1XJY080YwGLkNw_5 = {
  Sup = (len = 8, reserved = 4611686018427387912)
  data = ([0] = 'c', [1] = 'o', [2] = 'u', [3] = 'n', [4] = 't', [5] = 'e', [6] = 'r', [7] = ':', [8] = '\0')
}

=> should show as { Sup = len=8, reserved = ..., data = "counter:" }
see related PR: Gdb pretty printers by krux02 · Pull Request #8263 · nim-lang/Nim

minor

• lldb seems to work with an app built via --debugger:native ; docs should clarify this (including nim --fullhelp | grep lldb)
• lldb app gives warning (for me, on OSX)ImportError: cannot import name _remove_dead_weakref
• remove ENDB related code since it is deprecated in favor of gdb,lldb ; this'll cleanup nim a bit EDIT: endb can be revived, it's useful

maybe related

• confusing error messages when using lines + --debugger:on fails with: error: expected expression confusing error messages when using lines + --debugger:on fails with: error: expected expression #7426

related

• [1] https://nim-lang.org/blog/2017/10/02/documenting-profiling-and-debugging-nim-code.html
• [2] https://reviews.llvm.org/D44321 (Support demangling for D symbols via dlopen) => PR I had that allowed demangling D symbols in lldb using as little lldb code as possible and moving most of the logic to a D plugin that's opened via dlopen) => could be adapted to support nim; (moved from Support demangling for D symbols via dlopen llvm-mirror/lldb#3)
• forum: [https://forum.nim-lang.org/t/1508](How to debug nim code?) => see
  env SHELL=/bin/bash gdb hello
  (gdb) tui enable
• very little info: https://hookrace.net/blog/what-makes-nim-practical/#debugging-nim