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<BODY lang=EN-NZ vLink=purple link=blue bgColor=#ffffff>
<DIV><FONT face=Arial size=2>Hi Stacey,</FONT></DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=stacey@cjntech.co.nz href="mailto:stacey@cjntech.co.nz">Stacey
Verner</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=delphi@ns3.123.co.nz
href="mailto:delphi@ns3.123.co.nz">NZ Borland Developers Group - Delphi
List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, February 16, 2007 11:34
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [DUG] Delphi Calling Convetion
is Weird!!</DIV>
<DIV><FONT face=Arial size=2></FONT><BR></DIV>
<DIV class=Section1>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">After an odd bug
and a bit of testing I have found that the parameters in Delphi (tested 6 and
2006) are evaluated very strangely.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">The 3<SUP>rd</SUP>
parameter is evaluated first followed by 4, 5, 6 etc and then the
2<SUP>nd</SUP> and then the 1<SUP>st</SUP>.</SPAN></P></DIV></BLOCKQUOTE>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">Always this order? Or
does it vary sometimes if there are a different number of parameters? or if the
mix of parameters varies, ie between static values, in-line expressions,
function invocations?</SPAN></P>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"><o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">This appears to be
because the default calling convention is <B>register</B> which (from the
documentation) puts up to 3 parameters in registers and the rest on the stack.
It seems to process the stack ones first from parameters 3 onwards (Why 3?
Shouldn’t it be 4 if we are putting 3 into registers. Must be only putting 2
in the registers), and then the first 2 in reverse order into the registers.
</SPAN></P></BLOCKQUOTE>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">It may be that the
two registers it uses for parameters 1 and 2 are also used in calculating
parameter addresses in any call; or used in evaluating expressions in
parameters; if so, parameters 1 and 2 can't be set into the registers until
all the rest of the parameters have been evaluated. Also, registers
containing parameters of the main function can't be set before calling any
functions in the parameters, if they will be used for parameters of those
functions.</SPAN></P>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">The documentation
also says that is supposed to pass the from left to right, but it obviously
doesn’t.</SPAN></P></BLOCKQUOTE>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">Do you mean the order
in which parameter expressions are evaluated? Yes, if that's defined, the
compiler should respect it. Or the documentation should be changed to included a
caveat about the possible results of the compiler's optimisation.</SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"></SPAN> </P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">You'd be safest to
call your functions and save their results in temporary variables which you then
pass to the main function. That way you can control the order of the side
effects yourself and it'll work whatever the compiler does.</SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"></SPAN> </P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"></SPAN> </P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">Brian</SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"></SPAN> </P>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">You can download an
example to see for yourself!<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"><A
href="http://www.verner.co.nz/download/FunctionCall.zip">http://www.verner.co.nz/download/FunctionCall.zip</A><o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">If you are
interested how we found this, we have a simple function that strips the first
delimited item from a string returning the item and removing it from the input
string. You can have a string something like:<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">LString :=
‘Stacey,G,Verner’;<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">and
call:<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">LFirstName :=
Extract(LString, ‘,’);<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">LInitial :=
Extract(LString, ‘,’);<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">LLastName :=
Extract(LString, ‘,’);<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">In this case if we
had a function like:<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">function
FullName(PFirstName, PInitial, PLastName: String):
String;<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">and you call it
with:<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">LName :=
FullName(Extract(LString, ‘,’), Extract(LString, ‘,’), Extract(LString,
‘,’));<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">then we’ll get the
wrong result.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial','sans-serif'">Stacey</SPAN><o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">Stacey
Verner
Ph: +64-9-4154790<BR>Software
Developer Fax:
+64-9-4154791<BR>
DDI:
+64-9-4154797<BR>
Email: </SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 'Times New Roman','serif'"><A
title=mailto:stacey@cjntech.co.nz
href="BLOCKED::mailto:stacey@cjntech.co.nz"><SPAN
style="FONT-SIZE: 10pt; COLOR: blue; FONT-FAMILY: 'Courier New'">stacey@cjntech.co.nz</SPAN></A><o:p></o:p></SPAN></P>
<DIV class=Section1>
<P class=MsoNormal><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">CJN Technologies
Ltd.</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 'Times New Roman','serif'"><o:p></o:p></SPAN></P></DIV>
<P class=MsoNormal><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'"><ns0:Street><ns0:address>PO
Box 302-278, North</ns0:address></ns0:Street> Harbour,
<ns0:City>Auckland</ns0:City> 1330, <ns0:place><ns0:country-region>New
Zealand</ns0:country-region></ns0:place><BR><ns0:Street><ns0:address>12
Piermark Drive, North</ns0:address></ns0:Street> Harbour,
<ns0:place><ns0:City>Auckland</ns0:City>, <ns0:country-region>New
Zealand</ns0:country-region></ns0:place><BR>Visit our website at </SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 'Times New Roman','serif'"><A
title=http://www.cjntech.co.nz/
href="BLOCKED::http://www.cjntech.co.nz/"><SPAN
style="FONT-SIZE: 10pt; COLOR: blue; FONT-FAMILY: 'Courier New'">http://www.cjntech.co.nz/</SPAN></A></SPAN><o:p></o:p></P>
<P>
<HR>
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