I set a small array and the program below is ok to go out of bounds.

—
program test;
type
   tarr = array of array of boolean;
var
  exa : tarr = ((false,false,true,true),(false,false,true,true),
  (true,true,false,true), (true,true,true,false));

begin

  writeln(exa[0,0],', ',exa[4,4]);
  writeln(low(exa),', ',high(exa));
  writeln(low(exa[4]),', ',high(exa[4]));

end.
—
Free Pascal Compiler version 3.2.2 [2024/09/11] for aarch64 Copyright (c) 1993-2021 by Florian Klaempfl and others Target OS: Darwin for AArch64
Compiling test.pp
Assembling test
Linking test
-macosx_version_min has been renamed to -macos_version_min ld: warning: -multiply_defined is obsolete
15 lines compiled, 0.3 sec
FALSE, TRUE
0, 3
0, 3

Regards
Pete

{$R+}  // range checking
{$Q+}  // overflow checking

----- Oorspronkelijk bericht -----
Van: "P Padil via fpc-pascal"
Aan: "discussions FPC-Pascal users"
Cc: "P Padil"
Verzonden: Maandag 19 oktober 2026 02:45:30
Onderwerp: [fpc-pascal] looks like a bug

I set a small array and the program below is ok to go out of bounds.

—
program test;
type
   tarr = array of array of boolean;
var
  exa : tarr = ((false,false,true,true),(false,false,true,true),
  (true,true,false,true), (true,true,true,false));

begin

  writeln(exa[0,0],', ',exa[4,4]);
  writeln(low(exa),', ',high(exa));
  writeln(low(exa[4]),', ',high(exa[4]));

end.
—
Free Pascal Compiler version 3.2.2 [2024/09/11] for aarch64 Copyright (c) 1993-2021 by Florian Klaempfl and others Target OS: Darwin for AArch64
Compiling test.pp
Assembling test
Linking test
-macosx_version_min has been renamed to -macos_version_min ld: warning: -multiply_defined is obsolete
15 lines compiled, 0.3 sec
FALSE, TRUE
0, 3
0, 3

Regards
Pete

I typically got an exception even w/o those flags. I might have gotten to complacent running w/o them set though.

As its a dynamic array, I would use SetLength on it, before assigning to its elements.

Cheers,
Peter

Peter Blackman via fpc-pascal schrieb am
Di., 20. Okt. 2026, 23:51:

The array is already initialized with the initialization directly following its declaration. A SetLength() is not necessary in that case.

Regards,
Sven

OK, but its initialised to 4x4.
0..4 is 5 I think.

Cheers,
Peter

Peter Blackman via fpc-pascal schrieb am
Mi., 21. Okt. 2026, 00:45:

That is indeed the case. Hadn't seen noticed that the code accesses the data at index 4. ^^'

Regards,
Sven