Mechanism to detect new threads

[aaalexandrov]

Use windows debugger interface to detect the debugee's threads.
Fall back to polling a toolhelp snapshot in case debugger interface can't attach of fails.
Fixes #4

[CyberShadow]

Amazing. Will look at this soon!

[CyberShadow]

Thanks! Do you think this should be an option? E.g., if someone starts profiling but later decides to attach a debugger, this will now not be possible AIUI. Though, I guess the old behavior is still possible if you just select all threads and profile with those threads. Maybe we only need to document it.

[rmitton]

If the debugger interface doesn't work out, I believe another option is to inject a custom mini DLL into the target's address space -- you can get thread creation notifications via its DllMain callback.

[aaalexandrov]

Thanks! Do you think this should be an option? E.g., if someone starts profiling but later decides to attach a debugger, this will now not be possible AIUI. Though, I guess the old behavior is still possible if you just select all threads and profile with those threads. Maybe we only need to document it.

Yes, my thinking was that you get the old behavior by selecting all existing threads and profiling them
but if you have an idea how to make this more obvious in the UI, I can implement it

[aaalexandrov]

If the debugger interface doesn't work out, I believe another option is to inject a custom mini DLL into the target's address space -- you can get thread creation notifications via its DllMain callback.

It works on my machine!!1
On a more serious note, it seems to work fine, except when there's already a debugger attached to the application. And if it fails for whatever reason, it should fall back to the old behavior.

[CyberShadow]

Yep, I think a note in the documentation should be enough. We can update the wiki after this is merged.

LGTM, I rebased on master and added a changelog entry. Let me know if that looks OK to you and we can merge.

[aaalexandrov]

It looks great, thank you :)

[aaalexandrov]

I also looked into how to make this work through dll injection. RenderDoc does this in production code, here's the code https://github.com/baldurk/renderdoc/blob/v1.x/renderdoc/os/win32/win32_process.cpp#L252-L297

[CyberShadow]

We can update the wiki after this is merged.

https://github.com/VerySleepy/verysleepy/wiki/User-Interface/_compare/daaf68544578d05a78639565cfba19de45eb7ec2...f4e42831d7657691c5f03a1f3a6ed33199aef7c4