<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Not quite. I just checked RTAllocator.m3 and it is pointer to methods at offset 0, followed by fields.<div>Heap header is at -ADRSIZE(Header).</div><div>The type information in RT0 is used to initialize the object instances.<br><div>
<br><div><div>On Mar 22, 2013, at 1:34 AM, Dragiša Durić <<a href="mailto:dragisha@m3w.org">dragisha@m3w.org</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><base href="x-msg://17/"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">It's not m3front, it's RT0.<div><br></div><div>First data field is at offset 0, and pointer to type information is at -BYTESIZE(POINTER). Type information records are specified in RT0.</div><div>
<br><div><div>On Mar 22, 2013, at 5:56 AM, Jay K wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div class="hmmessage" style="font-size: 12pt; font-family: Calibri; "><div dir="ltr">layout of objects?<br><br><br><br>How are Modula-3 objects layed out?<br>i.e. "OBJECT"/"METHODS"/"OVERRIDES"<br>I skimmed m3front and it wasn't obvious.<br><br><br><br>A common way for C++ "objects" to be layed out,<br>in the face of no RTTI and only single inheritance,<br>and virtual functions, is that a pointer to a record<br>of function pointers is first in the record.<br><br><br>Like this:<br><br><br>class Type<br>{<br>virtual void F1();<br>virtual void F2();<br>int data1;<br>int data2;<br>};<br><br><br>ends up lik more this:<br><br><br>struct TypeFunctions<br>{<br> void (*F1)(Type*);<br> void (*F2)(Type*);<br>};<br><br><br>struct Type<br>{<br>TypeFunctions* Functions; /* always first,<br>or at least a fixed offset, and located independent<br>of the size of the data; could also be at "-1" or such */.<br>int data1;<br>int data2;<br>};<br><br><br>Type* x;<br>x->F1();<br><br><br>=><br>x->Functions->F1(x);<br><br><br>Functions added in more derived types go at the end.<br>Ditto for data.<br>In the absence of multiple-inheritance and RTTI, it is simple and predictable.<br>(RTTI makes only small modifications.)<br><br><br>Looking through m3front, it wasn't at all obvious if it works this way.<br><br><br>I would like to declare something in C (or possibly C++, but not likely),<br>such that I might actually recognize the various low level operations<br>and "uncompile" it back to a typeful/typesafe form, like the above C++<br>to C transform.<br><br><br><br>I can't likely uncompile to C++ with virtual functions,<br>because the actual layout in C++ is not guaranteed.<br><br><br><br>Granted, I am being lazy.<br>I should/could compile some small samples.<br>But I might not get the entire story that way.<br><br><br><br>Thanks,<br>- Jay<br><br></div></div></span></blockquote></div><br></div></div></blockquote></div><br></div></div><br><br><div>
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