<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">I think it's referring to a "moving" garbage collector (as opposed to a "non-moving" garbage collector that never moves/relocates objects.) The difference is that for a moving one, all pointers need to be tracked and potentially updated, whereas for a non-moving one, it's sufficient that at least one pointer to a live object is seen (when there may be other pointers to the same object elsewhere) for correctness.</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Oct 18, 2019 at 2:12 AM Yafei Liu via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><p style="margin:0px 0px 1em;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:Arial,"Helvetica Neue",Helvetica,sans-serif;font-size:15px;vertical-align:baseline;box-sizing:inherit;clear:both;color:rgb(36,39,41)">Hi all,</p><p style="margin:0px 0px 1em;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:Arial,"Helvetica Neue",Helvetica,sans-serif;font-size:15px;vertical-align:baseline;box-sizing:inherit;clear:both;color:rgb(36,39,41)">I'm investigating on integrating a gc to my llvm project, and when I read <a href="http://llvm.org/docs/Statepoints.html" rel="nofollow noreferrer" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;color:rgb(0,89,153)" target="_blank">this document</a>, one sentence confused me:</p><blockquote style="margin:0px 0px 10px;padding:10px;border-width:0px 0px 0px 2px;border-top-style:initial;border-right-style:initial;border-bottom-style:initial;border-left-style:solid;border-top-color:initial;border-right-color:initial;border-bottom-color:initial;border-left-color:rgb(255,235,142);font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:Arial,"Helvetica Neue",Helvetica,sans-serif;font-size:15px;vertical-align:baseline;quotes:none;box-sizing:inherit;background-color:rgb(255,248,220);color:rgb(36,39,41)"><p style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;clear:both">However, for a collector which wishes to relocate objects directly reachable from running code, a higher standard is required.</p></blockquote><p style="margin:0px 0px 1em;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:Arial,"Helvetica Neue",Helvetica,sans-serif;font-size:15px;vertical-align:baseline;box-sizing:inherit;clear:both;color:rgb(36,39,41)">I don't understand what the move "relocate objects directly reachable from running code" trying to do.</p><p style="margin:0px 0px 1em;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:Arial,"Helvetica Neue",Helvetica,sans-serif;font-size:15px;vertical-align:baseline;box-sizing:inherit;clear:both;color:rgb(36,39,41)">For my information, the concept "relocate" means the gc pointer refereed to a new location of an object, for example:</p><p style="margin:0px 0px 1em;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:Arial,"Helvetica Neue",Helvetica,sans-serif;font-size:15px;vertical-align:baseline;box-sizing:inherit;clear:both;color:rgb(36,39,41)">in Java:</p><pre style="margin-top:0px;margin-bottom:1em;padding:12px 8px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:Consolas,Menlo,Monaco,"Lucida Console","Liberation Mono","DejaVu Sans Mono","Bitstream Vera Sans Mono","Courier New",monospace,sans-serif;font-size:13px;vertical-align:baseline;box-sizing:inherit;width:auto;max-height:600px;overflow:auto;background-color:rgb(239,240,241);border-radius:3px;color:rgb(36,39,41)"><code style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:Consolas,Menlo,Monaco,"Lucida Console","Liberation Mono","DejaVu Sans Mono","Bitstream Vera Sans Mono","Courier New",monospace,sans-serif;vertical-align:baseline;box-sizing:inherit;white-space:inherit">Foo foo = new Foo();

foo = new Foo(); // ---> a relocation happens
</code></pre><p style="margin:0px 0px 1em;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:Arial,"Helvetica Neue",Helvetica,sans-serif;font-size:15px;vertical-align:baseline;box-sizing:inherit;clear:both;color:rgb(36,39,41)">So can anyone explain what the "relocate objects directly reachable from running code" trying to do?</p></div>
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</blockquote></div>