constant declarations not working as they do in Delphi

[440bx]

Hello,

FPC will not compile the following program:

Code: Pascal  [Select][+][-]

1. {$APPTYPE CONSOLE}
2.  
3. program ArrayConstError;
4.  
5. procedure DoIt;
6. const
7.   LINE_CNT   = 2;
8.  
9.   DataBuf    : packed array[1..LINE_CNT] of packed array[0..1023] of char
10.     = (#0, #0);
11.  
12.   // FPC does NOT accept this construction.  Delphi 2.0 does.
13.  
14.   DataArray  : packed array[1..LINE_CNT] of pchar
15.     = (DataBuf[1], DataBuf[2]);
16.  
17. begin
18.   writeln(DataBuf[1]);
19.   writeln(DataBuf[2]);
20.  
21.   writeln(DataArray[1]);
22.   writeln(DataArray[2]);
23. end;
24.  
25. begin
26.   DoIt;
27. end.
28.  

When attempting to compile the program above, FPC returns the following errors:

Code: Pascal  [Select][+][-]

1. Compile Project, Mode: Default, Target: lib\i386-win32\ArrayConstError.exe: Exit code 1, Errors: 2
2. ArrayConstError.lpr(13,18) Error: Incompatible types: got "Array[0..1023] Of Char" expected "PChar"
3. ArrayConstError.lpr(13,30) Error: Incompatible types: got "Array[0..1023] Of Char" expected "PChar"
4.  

Delphi version 2.0 compiles it without complaint.    I do not know if it compiles with other versions of Delphi.  Assistance to determine if it does or not is appreciated.

Should this be considered a "Delphi compatibility mode" bug ?

[engkin]

I don't see mode Delphi around the top, isn't it needed?

[440bx]

I don't see mode Delphi around the top, isn't it needed?

I tried it.  It didn't make any difference.

[Cyrax]

Changing your code to this makes it to compile successfully. FPC 3.3.1 trunk r41244 (i386-linux, i386-win32).

Code: Pascal  [Select][+][-]

1. ...
2. DataArray  : packed array[1..LINE_CNT] of pchar
3.     = (@DataBuf[1], @DataBuf[2]);
4. ...
5.  

[440bx]

Changing your code to this makes it to compile successfully. FPC 3.3.1 trunk r41244 (i386-linux, i386-win32).

Code: Pascal  [Select][+][-]

1. ...
2. DataArray  : packed array[1..LINE_CNT] of pchar
3.     = (@DataBuf[1], @DataBuf[2]);
4. ...
5.  

You're right, it does but, I don't think it should be necessary.  Even when specifying {$MODE DELPHI} it doesn't compile.  I believe it should.

Strictly from a compiler's definition viewpoint, FPC - as Delphi does - considers zero based arrays of char to be assignment compatible with pchar, because of that, the use of the address of operator should not be necessary.

ETA: I am using FPC v3.0.4 under Windows 7 64bit.

@Cyrax: thank you, I do appreciate your offering a solution.

[ASerge]

Delphi version 2.0 compiles it without complaint.    I do not know if it compiles with other versions of Delphi.

Delphi 10.3 also comple and code work right.

Strictly from a compiler's definition viewpoint, FPC - as Delphi does - considers zero based arrays of char to be assignment compatible with pchar, because of that, the use of the address of operator should not be

I agree with you, it is somewhat wrong that need to specify the @. This will show garbage:

Code: Pascal  [Select][+][-]

1. {$APPTYPE CONSOLE}
2. program ArrayConstError;
3.  
4. procedure DoIt;
5. const
6.   LINE_CNT = 2;
7.   DataBuf: packed array[1..LINE_CNT] {of packed array[0..1023] of Char} of PChar
8.     = ('Some'#0, #0);
9.   DataArray: packed array[1..LINE_CNT] of PChar = (@DataBuf[1], @DataBuf[2]);
10. begin
11.   Writeln(DataBuf[1]);
12.   Writeln(DataArray[1]);
13. end;
14.  
15. begin
16.   DoIt;
17.   Readln;
18. end.

[440bx]

Delphi 10.3 also comple and code work right.

Thank you for checking the behavior in other versions of Delphi.   Given that the discrepancy is consistent, I will report it as a bug.

This will show garbage:

Code: Pascal  [Select][+][-]

1. {$APPTYPE CONSOLE}
2. program ArrayConstError;
3.  
4. procedure DoIt;
5. const
6.   LINE_CNT = 2;
7.   DataBuf: packed array[1..LINE_CNT] {of packed array[0..1023] of Char} of PChar
8.     = ('Some'#0, #0);
9.   DataArray: packed array[1..LINE_CNT] of PChar = (@DataBuf[1], @DataBuf[2]);
10. begin
11.   Writeln(DataBuf[1]);
12.   Writeln(DataArray[1]);
13. end;
14.  
15. begin
16.   DoIt;
17.   Readln;
18. end.

Unfortunately, in that case, FPC and Delphi behave the same way.  The use of @ is incorrect but, I reported that problem/bug a while back and, it doesn't look like that problem/bug will be corrected because it is consistent with Delphi.