[fpc-devel] Incompatible assignments but no compile error (char array and shortstring)

[Sven Barth]

Am 16.04.2022 um 22:35 schrieb Wayne Sherman via fpc-devel:
> Tested with fpc 3.3.1 trunk (as of 2022-Mar-12) and 3.2.2 stable.
> Ubuntu 20.04 64-bit
>
> Good compile time error checking is one of the wonderful things about
> Pascal.  But some char array and shortstring assignments which are not
> size compatible do not produce a compile error as expected.  Please
> see below.
>
> {$mode objfpc}{$H+}
> type
>    TCharArray8    = packed array[0..7] of Char;
>    TCharArray9    = packed array[0..8] of Char;
>    TShortString8  = string[8];
>
> const
>    StringConst8 = '12345678';
>    StringConst9 = '123456789';
>
>    CharArrayConst8a: TCharArray8 = '12345678';
>    CharArrayConst8b: TCharArray8 = StringConst8;
>    CharArrayConst8c: TCharArray8 = ('1','2','3','4','5','6','7','8');
>
>    //CharArrayConst8d: TCharArray8 = '123456789';   //compile error as expected
>    //CharArrayConst8e: TCharArray8 = StringConst9;  //compile error as expected
>    //CharArrayConst8f: TCharArray8 =
> ('1','2','3','4','5','6','7','8','9'); //compile error as expected
>
>    ShortStringConst8a: TShortString8 = '12345678';
>    ShortStringConst8b: TShortString8 = StringConst8;
>    ShortStringConst8c: TShortString8 = '123456789';   //did not get
> expected compile error (bug?)
>    ShortStringConst8d: TShortString8 = StringConst9;  //did not get
> expected compile error (bug?)
>
> var
>    CharArrayVar8:   TCharArray8;
>    CharArrayVar9:   TCharArray9;
>    ShortStringVar8: TShortString8;
>
> begin
>    CharArrayVar8 := '12345678';
>    CharArrayVar8 := StringConst8;
>    CharArrayVar8 := ['1','2','3','4','5','6','7','8'];  //requires fpc 3.3.1
>    CharArrayVar8 := CharArrayConst8c;
>
>    //CharArrayVar8 := ['1','2','3','4','5','6','7','8','9']; //compile
> error as expected
>    CharArrayVar8 := '123456789';   //did not get expected compile error (bug?)
>    CharArrayVar8 := StringConst9;  //did not get expected compile error (bug?)
>
>    CharArrayVar8 := ShortStringVar8;
>    ShortStringVar8 := CharArrayVar8;
>
>    ShortStringVar8 := '12345678';
>    ShortStringVar8 := CharArrayConst8a;
>    ShortStringVar8 := TCharArray8(['1','2','3','4','5','6','7','8']);
> //requires fpc 3.3.1
>
>    ShortStringVar8 := '123456789';   //did not get expected compile error (bug?)
>    ShortStringVar8 := CharArrayVar9; //did not get expected compile error (bug?)
>    ShortStringVar8 :=
> TCharArray9(['1','2','3','4','5','6','7','8','9']); //did not get
> expected compile error (bug?) (requires fpc 3.3.1)
>
> end;
>
> Should I open a couple of bug reports?

For ShortString types it is by design that they're truncated implicitely 
(the most that current Delphi versions do is issue a warning). However 
the assignments to the static char array should be checked.

Regards,
Sven