[Lazarus] PascalScript on Win x64

Alexander Hofmann alexander.hofmann at new-h.de
Tue Sep 4 14:24:52 CEST 2012

Hi there.

This is a cross-post (cross-mail ?) to
http://www.lazarus.freepascal.org/index.php/topic,17978.0.html as I got
the hint there that it might be better to ask on the list instead of in
the forum, at least concerning the calling conventions - but I'll ask
the whole lot, anyway; I hope that's ok.

Has anyone successfully used PascalScript with Lazarus Classes (e.g.
TForm, TButton) on Win x64?

I can compile the downloadable latest stable version from RemObject's
website (the one with the EXE-Installer) as well as the latest
development version from https://github.com/remobjects/pascalscript OR
(that's not in the Forum) the PascalScript-version included in Lazarus'
SVN, no Problem there, after two small changes in x64.inc (see below).
Running the script works, adding user defined functions (and calling
them!) is OK, too.

But as soon as I try to Create forms and objects, like the following
script, the Program crashes with a SIGSEGV.

|program Script;

  f:=TForm.CreateNew(nil); //<- Works
  b:=TButton.Create(f); //<- crash

Crash in the Program is here:

000000000044F900 4883ec38                 sub    $0x38,%rsp
000000000044F904 48895c2420               mov    %rbx,0x20(%rsp)
000000000044F909 4889742428               mov    %rsi,0x28(%rsp)
000000000044F90E 4889cb                   mov    %rcx,%rbx
000000000044F911 4889d6                   mov    %rdx,%rsi
000000000044F914 4889da                   mov    %rbx,%rdx
000000000044F917 4889f1                   mov    %rsi,%rcx
000000000044F91A 4889f0                   mov    %rsi,%rax
000000000044F91D 488b00                   mov    (%rax),%rax
000000000044F920 ff9068010000             callq  *0x168(%rax)  <-- crash| 

Am I doing anything wrong? The same Script runs fine when the
Application was compiled with x86 Lazarus 1.0.
By the way: creating a TObject with e.g. o:=TObject.Create doesn't break
at al.

Interestingly, when I start debugging
<SomeClass>.Create(aOwner:TComponent)-Type of Constructors, there is
some difference in the Register values, depending on whether the
Constructor was called from "pure" FPC-Code or the Script (at least so
it seems):
o Called from FPC: rcx: 0 (nil), rdx: Class Reference, r8: Value of aOwner
o Called from Script: rcx: Class Reference, rdx: 1 (!?), r8: Value of
aOwner (at least so it seems)

Is there any difference in the calling convention on x64-Systems between
Delphi and Lazarus? I could only find the "standard" information on
Windows x64 calling conventions, without special care of constructors,
if there is any...

Did anybody else stumble about that problem before? Thanks for your help!

Index: x64.inc
--- x64.inc    (revision 38441)
+++ x64.inc    (working copy)
@@ -14,7 +14,7 @@
   _RCX, _RDX, _R8, _R9: IPointer;
   var _XMM0: Double;
   _XMM1, _XMM2, _XMM3: Double;
-  aStack: Pointer; aItems: IntPtr); assembler; {$IFDEF
+  aStack: Pointer; aItems: PtrUInt); assembler; {$IFDEF
 (* Registers:
     RCX: Address
@@ -37,7 +37,7 @@
   mov rdx, aStack
   jmp @compareitems
-  push [rdx]
+  push qword ptr [rdx]
   dec rcx
   sub rdx,8

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