1431967 - Consider adding a JS testing function that dumps C++ backtrace

Status: NEW

(Core :: JavaScript Engine, enhancement, P3)

Description

[Tooru Fujisawa [:arai]]

While debugging browser bugs (that may be multi-process), I often wanted to see C++ backtrace of the certain point in JS, to see how the code is executed (like, in which MicroTask checkpoint).
so, it might be nice to have a testing function that dumps C++ function, inside Cu.getJSTestingFunctions(),
similar to Cu.getJSTestingFunctions().backtrace() that dumps JS backtrace.

something like:
  await promise_for_mousedown_event;
  Cu.getJSTestingFunctions().dumpNativeBacktrace();

Comment 1

[Tooru Fujisawa [:arai]]

https://searchfox.org/mozilla-central/rev/b7e3ec2468d42fa59d86c03ec7afeb209813f1d4/xpcom/base/nsTraceRefcnt.cpp#881
wcpan told me that there's similar function provided in C++.
we could expose it via Components.utils.

Comment 2

[Tooru Fujisawa [:arai]]

Attachment: WIP patch (but uses different way)

fwiw, here's WIP patch that dumps backtrace,
but I'll try nsTraceRefcnt::WalkTheStack's way.