Re: Debug Interface for the mozjs, how to start/stop/pause/continue the js engine

Thanks for your input !

So if I read you correctly for the following simple scenario :
- A) user gives me code =

- B) the code is executed in mozjs
- C) while executing, the user press pause
- D) the code is paused in mozjs
- E) the user =AB step over =BB

B) several steps: =

- I should initialize the engine, register all my utility functions (e.g. t=
hose managing events) and set the debugger (with code like the one in https=
://developer.mozilla.org/en-US/docs/Tools/Debugger-API/Tutorial-Breakpoint)=
 through a call to JS::Evaluate
- then I give the user code to the engine through a call to JS::Evaluate
- immediately a "onNewScript" event is triggered (in ./Debugger.md)

C) normally my =AB callback =BB on onStep (through a onEnterFrame  like in =
js/src/jit-test/tests/debug/Frame-onStep-01.js) ignore the "steps"
D) but after the user order, I block the mozjs library by not returning fro=
m my callback ? Is it the trick ?
   In js/src/doc/Debugger/Debugger-API.md, it is said that "Both the debugg=
ee and the code using `Debugger` to observe it must run in the same thread"=
 (the code "using the Debugger" is mine I suppose), so no risks of corrupti=
on.
E) and so on

Did I understand correctly ?


Le lundi 6 avril 2020, 16:19:47 CEST Nicolas B. Pierron a =E9crit :
> Hi,
> =

> SpiderMonkey does have a Debugger interface. This interface is available =
from JavaScript code to inspect other code which is running in the same eng=
ine.
> =

> I am no expert in the Debugger, but I would reading the documentation[1] =
to find which function seems interesting and checking the test suite[2] to =
find example of usage.
> =

> Firefox uses SpiderMonkey and uses this interface to implement its Debugg=
er. However it adds extra complexity to it, in order to handle Debug from a=
 different process. You can find some examples using the Debugger API [3] b=
ut they would contains extra code which is specific to Firefox.
> =

> The Debugger API works using callbacks. Thus if you want to stop at a giv=
en location, you register a callback using `Debugger.Script.setBreakpoint`,=
 which would gives you a `Debugger.Frame` as argument of the `hit` function=
. Then you can register the `onStep` callback there and continue this way. =
 I am sure some improvement could be made to make this API more async-await=
 friendly. However, Generators and Promises did not exists at the time.
> =

> [1] https://developer.mozilla.org/en-US/docs/Tools/Debugger-API
> [2] https://searchfox.org/mozilla-central/source/js/src/jit-test/tests/de=
bug
> [3] https://developer.mozilla.org/en-US/docs/Tools/Debugger-API/Tutorial-=
Breakpoint
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> =