View Issue Details

IDProjectCategoryView StatusLast Update
0038576FPCLCLpublic2021-03-22 18:46
ReporterReiner Sombrowsky Assigned ToFlorian  
Status resolvedResolutionfixed 
Fixed in Version3.3.1 
Summary0038576: Cannot use TDataModule (Lazarus Revision: 64727, FPC Revision: 48871)
DescriptionIf I use TDataModule then unit cannot be saved "Access violation"
TagsNo tags attached.
Fixed in Revision
Attached Files


has duplicate 0038582 closedBart Broersma Lazarus [macOS aarch64] Lazarus BIGIDE executable dies on startup 
has duplicate 0038588 resolvedJuha Manninen Lazarus Crash when saving DataModule 


Reiner Sombrowsky

2021-03-03 11:01


lazarus.png (3,869 bytes)   
lazarus.png (3,869 bytes)   

Juha Manninen

2021-03-03 11:29

reporter   ~0129342

I cannot reproduce. Must be an FPC issue.
Please test with released FPC.

Reiner Sombrowsky

2021-03-03 13:03

reporter   ~0129344

Hello Juha Manninen,
thank you for your information. I tried it with my last previous FPC-Revision 48802.
It works correctly. I dont know in which Revision between 48802 and 48871 this error
was produced. Perhaps you can inform the FPC developers.
R. Sombrowsky

Juha Manninen

2021-03-03 17:06

reporter   ~0129360

I moved this to FPC project.
It would help if you bisect between 48802 and 48871 to find the exact guilty revision.


2021-03-03 19:57

reporter   ~0129362

I got following error when starting Lazarus with OPM
[FORMS.PP] ExceptionOccurred
  Exception=Error reading MainDM.Height: Access violation
  Stack trace:
  $000000000070F48E INITLAZRESOURCECOMPONENT, line 3180 of lresources.pp
  $0000000000706741 INITRESOURCECOMPONENT, line 798 of lresources.pp
  $00000000015F3D7F ONLINEPACKAGEMANAGERINTF_$$_init$, line 78 of onlinepackagemanagerintf.pas
TApplication.HandleException: EReadError
Error reading MainDM.Height: Access violation
  Stack trace:
  $000000000070F48E INITLAZRESOURCECOMPONENT, line 3180 of lresources.pp
  $0000000000706741 INITRESOURCECOMPONENT, line 798 of lresources.pp
  $00000000015F3D7F ONLINEPACKAGEMANAGERINTF_$$_init$, line 78 of onlinepackagemanagerintf.pas
Exception at 00000000005473CA: EReadError:
Error reading MainDM.Height: Access violation.

Failing revision is 48841

Reiner Sombrowsky

2021-03-04 16:17

reporter   ~0129382

Last edited: 2021-03-04 16:18

View 2 revisions

After a lot of tries I found that the last correct FPC-revision was 48840.
The FPC-revision 48841 was the first with this error.
The Lazarus-revision was 64743.
The autor of FPC-revision 48841 was "florian" on Sundy 28.02.2021

Trevor Roydhouse

2021-03-05 09:20

reporter   ~0129392

I needed to revert FPC to this commit:

commit baf2f57fa98fdc49f2714a59f5df69eb2b88a73a
Author: Tomas Hajny <>
Date: Sun Feb 28 10:29:59 2021 +0000

      * align shortname to previous releases
git-svn-id: 3ad0048d-3df7-0310-abae-a5850022a9f2

to be able to build and execute the bigide Lazarus version.

Juha Manninen

2021-03-05 17:43

reporter   ~0129400

r48841 is a new optimization. If you build Lazarus without optimization, does it work?
Next you must isolate the error into a smaller test program.


2021-03-05 22:06

reporter   ~0129411

A few tests:
Lazarus-2.1-64751_fpc-3.3.1-48880 optimized -- crash
Lazarus-2.1-64751_fpc-3.3.1-48880 normal -- crash
Lazarus-2.1-64751_fpc-3.3.1-48880 r48841_revert.patch normal -- ok
Lazarus-2.1-64751_fpc-3.3.1-48880 r48841_revert.patch optimized -- ok

Something with the side effect detection is wrong:
The pattern
        (a and b) or (c and not(b)) -> c xor ((c xor a) and b)
is matched by
        (Assigned(Ancestor) and (FDPPI<>Ancestor.FDPPI)) or
               (not Assigned(Ancestor) and (FDPPI<>96));

So the field access is not protected by the short-circuit of Assigned(Ancestor).

Sven Barth

2021-03-05 23:56

manager   ~0129418

(fixed "TDataModul" in title and description to be "TDataModule")


2021-03-06 15:49

administrator   ~0129436

Thanks everybody for the analysis. Can you please check/confirm that r48884 fixes the issue?


2021-03-06 16:04

administrator   ~0129437

Sorry, I needed a few more trials, please test with at least r48886.

Reiner Sombrowsky

2021-03-06 17:25

reporter   ~0129439

Hi florian,
I checked the Lazarus Rev. 64756 and FPC Rev. 48887
It works correct.
Thank you.


2021-03-06 17:38

reporter   ~0129441

Aye, can confirm, seems to be fixed. Thanks!


2021-03-06 19:11

reporter   ~0129450


Trevor Roydhouse

2021-03-06 22:37

reporter   ~0129455

Failure :(

Apple aarch64, macOS 11.2.2 (Big Sur).

Lazarus executable built with the bigide argument still dies on startup:

trev@macmini8 [/Users/trev/laz_trunk] $ ./lazarus
[FORMS.PP] ExceptionOccurred
  Exception=Error reading MainDM.Height: Access violation
  Stack trace:
TApplication.HandleException: EReadError
Error reading MainDM.Height: Access violation
  Stack trace:
Exception at 00000001030888F4: EReadError:
Error reading MainDM.Height: Access violation.

(lldb) target create "./lazarus"
Current executable set to '/Users/trev/laz_trunk/lazarus' (arm64).
(lldb) r
Process 13892 launched: '/Users/trev/laz_trunk/lazarus' (arm64)
Process 13892 stopped
* thread 0000001, queue = '', stop reason = EXC_BAD_ACCESS (code=1, address=0x70)
    frame #0: 0x000000010010a2a8 lazarus`CLASSES$_$TDATAMODULE_$__$$_DEFINEPROPERTIES$TFILER + 120
-> 0x10010a2a8 <+120>: ldr w2, [x0, #0x70]
    0x10010a2ac <+124>: cmp w2, w1
    0x10010a2b0 <+128>: cset w2, ne
    0x10010a2b4 <+132>: cmp w1, #0x60 ; =0x60
Target 0: (lazarus) stopped.


2021-03-07 09:45

administrator   ~0129459

@Trevor: So this worked with 48840 ?

Trevor Roydhouse

2021-03-07 11:48

reporter   ~0129468

The last version I had working was 48839 (according to git - not sure whether the svn/git versioning lines up perfectly).

Trevor Roydhouse

2021-03-07 12:05

reporter   ~0129471

48440 builds but cannot compile Lazarus due to the fpcres binary being killed on startup. I managed to get it working by rsync'ing a copy from /usr/local/share/fpcsrc/3.3.1/utils/fpcres/bin/aarch64-darwin/fpcres to /usr/local/bin. Then, yes, 48440 builds a bigide Lazarus executable that does not die on startup and seems to compile working native arm apps without issue.


2021-03-15 22:24

administrator   ~0129699

I really cannot reproduce it (though I am testing aarch64-linux and not aarch64-darwin, but there should be no difference in this regard). r48841 produces

    ldr w1,[x19, 0000144]
// [103] HavePPIData:=(Assigned(Ancestor) and (FDPPI<>Ancestor.FDPPI)) or
    ldr w2,[x0, 0000144]
    cmp w2,w1
    cset w2,ne
// [104] (not Assigned(Ancestor) and (FDPPI<>96));
    cmp w1,0000096
    cset w1,ne
    eor w2,w1,w2
    cmp x0,#0
    cset w0,ne
    and w0,w0,w2
    eor w21,w1,w0

which is not valid. But with r48887 at least all problems are fixed and I get:

// [103] HavePPIData:=(Assigned(Ancestor) and (FDPPI<>Ancestor.FDPPI)) or
    cbz x0,.Lj5424
    ldr w1,[x19, 0000144]
    ldr w2,[x0, 0000144]
    cmp w1,w2 .Lj5425
// [104] (not Assigned(Ancestor) and (FDPPI<>96));
    cbnz x0,.Lj5426
    ldr w0,[x19, 0000144]
    cmp w0,0000096 .Lj5425

Trevor Roydhouse

2021-03-15 23:54

reporter   ~0129701

Anything more I can do to help?

I can provide VNC access to an M1 Mac mini if it helps.


2021-03-20 10:12

administrator   ~0129769

My knowledge about MacOS X is too little to make use of this. Did you really check that the compiler is up-to-date and that the classes.o is recompiled by this compiler? Else if a trunk compiler still matches this pattern wrong only in this case on aarch64-darwin, then there must be something really really weird going on.

Trevor Roydhouse

2021-03-22 09:18

reporter   ~0129820

I have found the issue after investigating why the newly compiled fpcres binary was being killed on startup. The Big Sur of macOS for m1 aarch64 will not run any unsigned code (luckily the linker automatically signs the executables with an ad hoc signature and generates. a matching cdhash (code directory hash).

The cdhash is used when macOS checks code before running it to verify that the contents of a binary have not changed since being code signed. The code signing information is hung off a vnode within the kernel, and modifying the file behind that cache causes the problem - you need a new vnode, which means a new file, that is, a new inode. So if the new executable gets copied over the old executable and the inode remains the same, the cdhash no longer matches and the application is killed on startup by the system. The same thing was happening with the Lazarus executable.

Sorry to have wasted your time Florian. The current FPC trunk version of Sun Mar 21 21:39:57 2021 compiles the trunk Lazarus bigide version successfully.


2021-03-22 18:46

administrator   ~0129831

Thanks for confirming :)

Issue History

Date Modified Username Field Change
2021-03-03 11:01 Reiner Sombrowsky New Issue
2021-03-03 11:01 Reiner Sombrowsky File Added: lazarus.png
2021-03-03 11:29 Juha Manninen Note Added: 0129342
2021-03-03 13:03 Reiner Sombrowsky Note Added: 0129344
2021-03-03 17:04 Juha Manninen Project Lazarus => FPC
2021-03-03 17:06 Juha Manninen Note Added: 0129360
2021-03-03 19:57 delfion Note Added: 0129362
2021-03-04 16:17 Reiner Sombrowsky Note Added: 0129382
2021-03-04 16:18 Reiner Sombrowsky Note Edited: 0129382 View Revisions
2021-03-05 07:25 Juha Manninen Relationship added has duplicate 0038582
2021-03-05 09:20 Trevor Roydhouse Note Added: 0129392
2021-03-05 17:43 Juha Manninen Note Added: 0129400
2021-03-05 18:39 Juha Manninen Relationship added has duplicate 0038588
2021-03-05 22:06 Martok Note Added: 0129411
2021-03-05 23:56 Sven Barth Product Version 2.1 (SVN) =>
2021-03-05 23:56 Sven Barth Summary Cannot use TDataModul (Lazarus Revision: 64727, FPC Revision: 48871) => Cannot use TDataModule (Lazarus Revision: 64727, FPC Revision: 48871)
2021-03-05 23:56 Sven Barth Description Updated View Revisions
2021-03-05 23:56 Sven Barth FPCTarget => -
2021-03-05 23:56 Sven Barth Note Added: 0129418
2021-03-06 15:49 Florian Status new => feedback
2021-03-06 15:49 Florian Note Added: 0129436
2021-03-06 16:04 Florian Note Added: 0129437
2021-03-06 17:25 Reiner Sombrowsky Note Added: 0129439
2021-03-06 17:25 Reiner Sombrowsky Status feedback => new
2021-03-06 17:38 Martok Note Added: 0129441
2021-03-06 19:11 delfion Note Added: 0129450
2021-03-06 22:37 Trevor Roydhouse Note Added: 0129455
2021-03-07 09:45 Florian Note Added: 0129459
2021-03-07 11:48 Trevor Roydhouse Note Added: 0129468
2021-03-07 12:05 Trevor Roydhouse Note Added: 0129471
2021-03-15 22:24 Florian Note Added: 0129699
2021-03-15 23:54 Trevor Roydhouse Note Added: 0129701
2021-03-20 10:12 Florian Note Added: 0129769
2021-03-22 09:18 Trevor Roydhouse Note Added: 0129820
2021-03-22 18:46 Florian Assigned To => Florian
2021-03-22 18:46 Florian Status new => resolved
2021-03-22 18:46 Florian Resolution open => fixed
2021-03-22 18:46 Florian Fixed in Version => 3.3.1
2021-03-22 18:46 Florian Note Added: 0129831