Not sure how to clean up legacy DDE codes
lazarus / 34-Windows

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PaulRowntree · 2019-10-02 13:57

I have been using some DDEML client codes for over two decades that
are based on some original Delphi classes; I converted this to lazarus
in 2011.  Code runs, but requires RangeChecking to be off, and it
gives many warnings about unsafe conversions etc.  I now read that the
use of the MakeProcInstance (and FreeProcInstance I assume) is
deprecated (
https://devblogs.microsoft.com/oldnewthing/20080207-00/?p=23533  ) but
I have no idea what the recommended way to do this under modern Win
system.  I am running Win 7-10, Laz 1.8.4

Here is the working but obsolete code fragment, from the bottom of my
DDEML unit.  The purpose is to initialize the DDE link, and to insert
the code into the exit chain mechanism.  The DDE system does not
function if a NIL CallBackPtr is passed to DDEInitialize as written. 
If it matters, I don't actually use the Advise functionality, so the
CallBackpROC is never used in my codes .. it is always based on direct
transactions with the DDE system.

Any suggestions or guidance would be greatly appreciated.  Thanks!

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i var   
CallBackPtr : Pointer;    ChainExit      : POINTER;{$S-}PROCEDURE
DDEML_ExitProc; far;begin  if DDEML_Instance <> 0 then   
DdeUninitialize(DDEML_Instance);   { Ignore the return value }   if
CallBackPtr <> nil then    FreeProcInstance(longint(CallBackPtr));  
ExitProc := ChainExit;END;{$S+} BEGIN{ install the exit codes }   
ChainExit := ExitProc;    ExitProc := @DDEML_ExitProc;  CallBackPtr :=
pointer( MakeProcInstance( longint(@CallBackProc), HInstance) );//
 CallBackPtr := NIL;  DDEML_INstance := 0; { Initialize the DDE and
setup the callback function. }  if CallBackPtr <> nil then   
DdeInitialize(@DDEML_Instance, PFNCallback(CallBackPtr),
AppClass_STANDARD,0);END.

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marcov · 2019-10-02 14:10

longint(@CallBackProc)  is wrong, since longint is 32-bit and
callbackproc is 64-bit on 64-bit systems.

It would be helpful to see the exact errors you get.

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PaulRowntree · 2019-10-02 14:44

Sorry ... first reply was a mess ...
There are no compile errors, but here are the 4 warnings
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
ddeml_laz.pas(389,30) Warning: Procedure type "FAR" ignored  *** this
is the DDEML_ExitProcddeml_laz.pas(395,22) Warning: Conversion between
ordinals and pointers is not portableddeml_laz.pas(406,44) Warning:
Conversion between ordinals and pointers is not
portableddeml_laz.pas(406,17) Warning: Conversion between ordinals and
pointers is not portableOddly, the MakeProcInstance and
FreeProcInstance API functions show that the parameters are defined as
longints according to the hover-help messages.  They both return
longint results as well.

Thanks!

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marcov · 2019-10-02 15:11

Things like FAR are 16-bits remnants. They should probably have been
cleared out after Windows 95 emerged :-)

It seems makeprocinstance and freeprocinstance are macros that in FPC
are converted to Pascal functions, and are essentially no ops (empty
functions that return whatever is passed to them.

Probably related to thunking allocation in Win3.1, which is now
largely considered obsolete too. (as is its successor Win9x)

So probably just leave out all the procinstance stuff, and simply just
run the ddeinitialize line only.

For reference,  here is the complete source code for those functions:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i   function
MakeProcInstance(p,i : longint) : longint;    begin     
 MakeProcInstance:=p;    end;  function FreeProcInstance(p : longint)
: longint;    begin       FreeProcInstance:=p;    end;

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PaulRowntree · 2019-10-02 15:20

That is great information marcov, thank you very much!  It is scary
that I was dragging around Win3.1 code, although it is just as scary
to know that I remember those days (and was so excited to be 'living
in the future').
Thanks again!