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asm from delphi to fpc
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Topic: asm from delphi to fpc (Read 2246 times)
nanobit
Full Member
Posts: 160
asm from delphi to fpc
«
on:
October 23, 2018, 08:26:32 am »
The following delphi asm code (to change the field TFreeObject.VMIndex: Integer)
does not compile with fpc. How could one port this?
Code: Pascal
[Select]
[+]
[-]
procedure
TFreedObject
.
GetVirtualMethodIndex
;
assembler
;
asm
Inc
(
VMIndex
)
;
Inc
(
VMIndex
)
;
Inc
(
VMIndex
)
;
Inc
(
VMIndex
)
;
Inc
(
VMIndex
)
;
Inc
(
VMIndex
)
;
Inc
(
VMIndex
)
;
Inc
(
VMIndex
)
;
Inc
(
VMIndex
)
;
Inc
(
VMIndex
)
;
jmp TFreedObject
.
VirtualMethodError
end
;
Logged
Thaddy
Hero Member
Posts: 14205
Probably until I exterminate Putin.
Re: asm from delphi to fpc
«
Reply #1 on:
October 23, 2018, 10:13:11 am »
Such code relies on very low level implementation detail and may even change between Delphi versions: it is bad code! in my opinion.
Since it relies on implementation detail it is not FPC compatible.
But you can use e.g. TObject.MethodAddress
Depends what you want?
[edit]
FPC Has a TypeOf() function that returns the VMT, so the index is something like (TYourObject.MethodAddress('methodname') - TypeOf(TYourObject)) div sizeOf(Pointer);
You can get the address and the VMT and subsequently the index.
That also means it is silly to use assembler for it.
«
Last Edit: October 23, 2018, 10:25:21 am by Thaddy
»
Logged
Specialize a type, not a var.
marcov
Administrator
Hero Member
Posts: 11383
FPC developer.
Re: asm from delphi to fpc
«
Reply #2 on:
October 23, 2018, 10:14:13 am »
Compile a small program that has a pascal version of the method with -Rintel -a and look at the generated code in the .s file.
Logged
Thaddy
Hero Member
Posts: 14205
Probably until I exterminate Putin.
Re: asm from delphi to fpc
«
Reply #3 on:
October 23, 2018, 10:22:44 am »
Marco, I did an edit. Would that work? [edit] No! but something can be done along those lines.
«
Last Edit: October 23, 2018, 11:33:44 am by Thaddy
»
Logged
Specialize a type, not a var.
nanobit
Full Member
Posts: 160
Re: asm from delphi to fpc
«
Reply #4 on:
October 23, 2018, 03:02:33 pm »
Unfortunately, I will give up. I wanted to port fastMM to Lazarus, but it compiles only without the FullDebugMode define. FullDebugMode is required to use detection of memory corruptions, the main reason I wanted to use it.
Logged
Thaddy
Hero Member
Posts: 14205
Probably until I exterminate Putin.
Re: asm from delphi to fpc
«
Reply #5 on:
October 23, 2018, 03:11:08 pm »
heaptrc.pp shows you how to detect memory corruption in much the same way. So examine that.
Also note the memory manager from Freepascal works internally different - not much but significant - from Delphi and is already fast (much faster than the default Delphi one once was before they changed to fastmm light) and it is cross-platform which fastmm isn't...
«
Last Edit: October 23, 2018, 03:29:40 pm by Thaddy
»
Logged
Specialize a type, not a var.
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asm from delphi to fpc
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