This works on my machine, but on travis linux gdb seems to exit 127, and on osx it appears to give different output.

The linux failures are because gdb isn't in the Dockerfile: this change is essentially a no-op. I'll submit a PR to jhass/crystal-build-docker later.

I don't have an osx machine to debug on (and due to it being apple they're very hard to get) so I think someone else will have to have a look at that.

Looks like the docker container needs --privileged to run. Using this flag looks fine as it's a temporary VM anyway and there's nothing particularly untrusted running in the container.

Unfortunately, this is why gdb doesn't work on osx. The instructions on how to codesign gdb appear to require using a GUI which isn't feasible. Maybe someone can experiment whether they can reliably automate this using security(1)? If not, simply disabling this on osx should work, although very unfortunate.

Looks like debug info is broken on 32bits. Should we just disable the specs on 32bit or attempt to fix it?

Similarly, on OSX it'll be hard to get the specs working. It seems it requires manual setup on most systems to enable gdb. We should probably disable these specs on osx by default but provide a way of enabling them for people who have a working gdb. Any thoughts on the best way to do this? A build flag?

Sigh, that would have been fantastic, but if the solution isn't portable across systems, the benefit is dubious, for writing tests, or for developers writing/fixing them to need a specific platform :(

Maybe gdb instrumentation, taking platform discrepancies into account, would perform better?

@ysbaddaden what do you mean by "gdb instrumentation"?

I meant opening a gdb session (e.g. gdbserver) then interact through the GDB Remote Serial Protocol. That should get us through platform discrepancies, but that would be a lot of work...

@ysbaddaden that won't help when GDB has insufficient permissions on osx and the debug info is broken on 32bit. It'd just give us the same wrong data, which would fail the specs.

I can disable this on OSX but it's pretty clear that debug info is actually broken on 32bit here, so we should investigate that. Or should we merge this so that we can detect 64bit regressions at least?

What's the status here, do we still want this?

I would still love this, but it needs to be checked whether these issues are now fixed or not