WIP: Prevent segfaults related to infinite marshal recursion

[seanmakesgames]

Creates a marshal stackdepth option, allowing protection against exceptional object structures. See testcases for examples.
Been a while since I've made changes in here, would love some critical eyes on the code.

[seanmakesgames]

After v8 ver upgrade, max data slots seem to have reduced. Need to refactor our usage and allocate some memory to track our runtime state per isolate.

[seanmakesgames]

Also, @SamSaffron the locale test you added is failing on my machine on the main branch. Is this expected?
darwin 10.15, ruby 2.6.5

[SamSaffron]

@seanmakesgames error is kind of expected until you update libv8-node, try installing latest and updating lockfile etc.

[SamSaffron]

I need some time to think about this, can you think of a way of introducing minimal levels of safety here without making this configurable? Maybe we just limit at 1000 depth unconditionally using a const or something like that and the patch can be simpler?

[seanmakesgames]

@seanmakesgames error is kind of expected until you update libv8-node, try installing latest and updating lockfile etc.

Got it. Thanks. I figured the dependency file would have forced the upgrade when I ran bundle.

[seanmakesgames]

I need some time to think about this, can you think of a way of introducing minimal levels of safety here without making this configurable? Maybe we just limit at 1000 depth unconditionally using a const or something like that and the patch can be simpler?

I can definitely put that together. For my uses I need 100. :)
I'll put together a few different PRs.

[seanmakesgames]

@seanmakesgames error is kind of expected until you update libv8-node, try installing latest and updating lockfile etc.

Got it. Thanks. I figured the dependency file would have forced the upgrade when I ran bundle.

I deleted my lock file and rebundled and am still having the error. What version of libv8-node am I looking for here?
Gemfile.lock.txt

[seanmakesgames]

@seanmakesgames error is kind of expected until you update libv8-node, try installing latest and updating lockfile etc.

Got it. Thanks. I figured the dependency file would have forced the upgrade when I ran bundle.

I deleted my lock file and rebundled and am still having the error. What version of libv8-node am I looking for here?
Gemfile.lock.txt

This was fixed by #200

[seanmakesgames]

I need some time to think about this, can you think of a way of introducing minimal levels of safety here without making this configurable? Maybe we just limit at 1000 depth unconditionally using a const or something like that and the patch can be simpler?

@SamSaffron I just tried to implement this with a fixed depth -- but I can't without #201 because we are at data slot max already: 4/4.

I need flags like MEM_SOFTLIMIT_VALUE and MEM_SOFTLIMIT_REACHED to be able to track the stack depth and report it back safely across thread contexts and such. I'll push my WIP -

[seanmakesgames]

I put the non-configurable stack max into #202 -- needs 201 to work. Happy to update them however.

[seanmakesgames]

implemented by #202