<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div dir="ltr"><meta http-equiv="content-type" content="text/html; charset=utf-8">Hi Marcel,<div dir="ltr"><br><blockquote type="cite">On Aug 18, 2021, at 5:25 AM, Marcel Taeumel <marcel.taeumel@hpi.de> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><span><div id="__MailbirdStyleContent" style="font-size: 10pt;font-family: Arial;color: #000000;text-align: left" dir="ltr">Hi all!<div class="mb_sig"></div><div><br></div><div>I kind of thought that objects sitting as arguments on active stack frames form strong references. </div></div></span></div></blockquote><div><br></div>Indeed they must.<div><br><blockquote type="cite"><div dir="ltr"><span><div id="__MailbirdStyleContent" style="font-size: 10pt;font-family: Arial;color: #000000;text-align: left" dir="ltr"><div>Yet, I have a kind of flaky callback test that raises doubts about this assumption.</div><div><br></div><div>Here is an example:</div><div> lib qsort: array compare: [:a :b | (a - b) sign].</div></div></span></div></blockquote><div><br></div>The block being nil inside the callback could imply that the lookup from thunk address to block yielded nil and be nothing to do with the stack no?</div><div><br><blockquote type="cite"><div dir="ltr"><span><div id="__MailbirdStyleContent" style="font-size: 10pt;font-family: Arial;color: #000000;text-align: left" dir="ltr"><div><br></div><div>Maybe it is some interference with GC and FFI callbacks ... Hmm... Anyway, sometimes, the block closure is already "nil" inside the callback when its time to evaluate... But mostly it works fine. :-)</div></div></span></div></blockquote><div><br></div>I can’t see what you’ve posted below. If displays as a white region. Can you post the stack? What’s the actual error message? If you look down the stack where does the nil block originate?</div><div><br><blockquote type="cite"><div dir="ltr"><span><div id="__MailbirdStyleContent" style="font-size: 10pt;font-family: Arial;color: #000000;text-align: left" dir="ltr"><div><br></div><div><img id="6da5b35a-282a-4bc8-8f88-d198fcb3189a" src="cid:89244823-a295-4c90-adf4-03d7e832b9c5" width="335" height="347" data-unique-identifier=""><br></div></div></span></div></blockquote><div><br></div>Mysterious ;-)</div><div><br><blockquote type="cite"><div dir="ltr"><span><div id="__MailbirdStyleContent" style="font-size: 10pt;font-family: Arial;color: #000000;text-align: left" dir="ltr"><div><br></div><div>Best,</div><div>Marcel</div></div></span></div></blockquote><br></div><div>Eliot</div><div>_,,,^..^,,,_ (phone)</div></div></body></html>