[2pt] Document luajit-gdb.py

[rosik]

The luajit-gdb.py isn't mentioned in doc. That's no good.

SME: @igormunkin

[@veod32]:
Introduced in release 2.4.1.
Summary from the release notes (LuaJIT section):

Introduce luajit-gdb.py extension with commands for inspecting LuaJIT internals. The extension obliges one to provide gdbinfo for libluajit, otherwise loading fails. The extension provides the following commands:

• lj-arch dumps values of LJ_64 and LJ_GC64 macro definitions
• lj-tv dumps the type and GCobj info related to the given TValue
• lj-str dumps the contents of the given GCstr
• lj-tab dumps the contents of the given GCtab
• lj-stack dumps Lua stack of the given lua_State
• lj-state shows current VM, GC and JIT states
• lj-gc shows current GC stats

More details in this cover letter

ToDo

• The luajit-gdb.py script can be mentioned in some documentation section related to LuaJIT -- research where.
• As for the script usage, there is an internal help that can be started from GDB (GNU Debugger). The help contains all the necessary info for developers, and there is no need to duplicate this in the Tarantool documentation.

[veod32]

@igormunkin
In 2.4.1 RN, the dev issue for luajit-gdb.py is not mentioned. Do we have any?

[igormunkin]

@igormunkin
In 2.4.1 RN, the dev issue for luajit-gdb.py is not mentioned. Do we have any?

No, we don't. Initially, it was a "by-product" of the coredump investigation.

@veod32, hope this cover letter will be helpful.

[veod32]

@veod32, hope this cover letter will be helpful.

Yes, it will, thanks! It's OK for the initial input. We'll get back to you later for this doc issue estimate.