Support OpenResty 1.15.8.1, which now defaults to GC64

[philipp-classen]

Disclaimer: I'm lacking understanding of the tools, but at least for a normal OpenResty installation on Ubuntu 18.04, it fixes the regression ("semantic error: unable to find member 'ptr32' for struct MRef") since the latest release for me.

refs #46

[agentzh]

@philipp-classen This breaks compatibility with earlier OpenResty versions. We'll need to be smarter here.

[philipp-classen]

@agentzh Yes, I'm sure you are right. As said, I'm lacking understanding of it and unfortunately I don't have the time to dig deeper.

We can close it. I still wanted to share it, maybe it helps someone out there who needs to profile the current version now and cannot wait. Until there is a proper fix, this hack might be useful.

[agentzh]

We're actually retiring this repo (as well as the openresty-systemtap-toolkit repo and others) in favor of the upcoming OpenResty Trace platform (with will have free access for OpenResty open source users).

[soulbird]

maybe you can use --without-luajit-gc64 option that can force close gc64. And this just for debugging

[agentzh]

@soulbird You can try OpenResty XRay which supports both GC64 and non-GC64 modes of LuaJIT. It provides a free trial.