Oops, let me try again, being a little less agricultural.<div><br><br><div class="gmail_quote">On Wed, Mar 7, 2012 at 1:57 AM, Stefan Marr <span dir="ltr"><<a href="mailto:smalltalk@stefan-marr.de">smalltalk@stefan-marr.de</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
Hi Eliot:<br>
<div class="im"><br>
On 07 Mar 2012, at 01:47, Eliot Miranda wrote:<br>
<br>
> But the flag is really useful for VM/image communication.<br>
</div>Right, that's what I want to use it for.<br>
Flagged methods will allow me to mark exit points from a special interpretation mode.<br>
In that special mode, I enforce certain additional semantics, but need to be able to disable that to get back to the normal mode.<br>
The flag seems to be a convenient way to do that.<br>
<div class="im"><br>
<br>
> This is related to the above. I've just added support to Squeak trunk for accessing the sign bit in the method header and using this as an additional flag.<br>
<br>
</div>Ehm, I am not completely with you. I think, I misunderstand something here, which header word exactly?<br>
<br>
I looked through the diff of VMMaker.oscog-eem.146 and see this line:<br>
^(objectMemory integerValueOf: (self headerOf: aMethodObj)) < 0<br>
<br>
Isn't that the mark bit for the GC? Or am I confusing something?<br></blockquote><div><br></div><div><span class="Apple-style-span" style="border-collapse:collapse;font-family:arial,sans-serif;font-size:13px">Yes, you're confusing the object header with the method header, which is unsurprising. headerOf: should really be called methodHeaderOf: but isn't (again history). So this is the sign bit in the method header (a SmallInteger) and is the bit next to the flag bit.</span> </div>
<div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">#headerOf: should be the first word of every object, right?<br></blockquote><div> </div><div><span class="Apple-style-span" style="border-collapse:collapse;font-family:arial,sans-serif;font-size:13px"><div>
You'd think, but no :)</div><div class="im" style="color:rgb(80,0,80)"></div></span></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
And at least in the RoarVM (I doubt that this is different from the standard interpreter), MarkBit is defined as (1 << 31), isn't that exactly the sign bit?<br></blockquote><div><br></div><div> <span class="Apple-style-span" style="border-collapse:collapse;font-family:arial,sans-serif;font-size:13px">Purely coincidental ;)</span></div>
<span class="Apple-style-span" style="border-collapse:collapse;font-family:arial,sans-serif;font-size:13px"><div class="im" style="color:rgb(80,0,80)"></div></span><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Thanks<br>
<font color="#888888">Stefan<br></font></blockquote><div> </div><div>-- </div></div>cheers,<div>Eliot</div><br>
</div>