@jhass raising an exception and catching is pretty expensive. Can we maybe check this without raising an exception? It might be a bit uglier/longer, but maybe speed is more important here.

Did you look at the logic in OpenSSL::SSL:Error? Are you really sure you want to duplicate it?

The other issue is that afaik you can't call LibSSL.ssl_get_error twice, neither LibCrypto.err_get_error. So if we fetch it here, we probably need the logic a third time in OpenSSL::SSL:Error taking the already fetched values...

Don't worry, let's leave it like this. If we later find a way to optimize it (if we find it causes slowdowns) then we'll fix it then.

The performance hit is only raising & rescueing, no?

begin
  case ret = LibSSL.ssl_shutdown(@ssl)
  when 1
    break
  when 0
    # retry
  else
    ex = OpenSSL::SSL::Error.new(@ssl, ret, "SSL_shutdown")
    raise ex unless ex.error.want_read? || ex.error.want_write?
  end
rescue e : Errno
  # ...
end

That's a bit better yeah, feel free to push from my side. However the common case will be that Errno is raised from OpenSSL::SSL::Error.new. Perhaps we should return either and override new instead, though OpenSSL::SSL::Error.new returning OpenSSL::SSL::Error|Errno is a bit ugly too.

@ysbaddaden Yes, though creating an exception builds a backtrace from the stack. But I think catching an exception is more expensive because the stack needs to be walked and checked (as far as I remember, @waj knows this much better). But yes, this way should be slightly faster than always raising.

Argh, I expected the backtrace to only be generated when raising, not when constructing the object. I verified and Exception.new already builds the callstack. Maybe we would like to change that?

Yeah, I think it should be harmless, and in fact more correct:

def foo
  Exception.new
end

def bar(ex)
  raise ex
end

ex = foo
bar(ex)

Ruby says:

foo.cr:6:in `bar': Exception (Exception)
    from foo.cr:10:in `<main>'

Crystal says:

 (Exception)
[4466977538] *CallStack::unwind:Array(Pointer(Void)) +82
[4466977441] *CallStack#initialize<CallStack>:Array(Pointer(Void)) +17
[4466977400] *CallStack::new:CallStack +40
[4466982204] *Exception#initialize<Exception>:CallStack +28
[4466982140] *Exception::new:Exception +92
[4466972153] *foo:Exception +9
[4466961818] __crystal_main +890
[4466971976] main +40

I'll change it, should be pretty easy.