Re: Assignment to array/record constants.

[Gaius Mulley]

Guy <guyfieri@getbackinthe.kitchen> writes:

> Hello again Gaius, due to my lack of experience with mailing lists I'm afraid 
> I just recently realized that when attempting to reply to your response to 
> me, I accidentally replied directly to your personal email instead of the 
> mailing list.
> Due to my email address's domain name, I think that it probably ended up in 
> your junk/spam folder, my mistake.
>
> However since then I have installed Debian and was indeed able to compile the 
> project mostly without issue, so in hindsight it seems that the latest GCC 
> sources just aren't too well suited for macOS (though I'm sure there were 
> quite a
> few things I was missing on my end).
>
> So today, the issue/question I had is a bit different and instead related to 
> the actual compiler frontend's behavior. One of the first things I happened 
> to try after the successful compilation was some features that I made 
> frequent use of
> in other languages I have used, that being array/record constants. I saw from 
> a Modula-2 ISO reference that the language also supported this via what it 
> calls "constant constructors". Just to see how the compiler would respond, I 
> tried
> assigning a value to some test constants I made, but to my surprise it didn't 
> complain and actually replaced its value with the new one from the program 
> body.
>
> More specifically, assignments to the constants in the body of the program 
> via a constant constructor ("constant := TypeName{...}") replaced the current 
> value, but assignments to individual components of the array/record didn't
> actually have an effect on the values. Running the test program in GDB. I 
> noticed the main procedure of executable programs seemed to be named 
> _M2_<program_name>_init, and was wondering if all array/record constructors
> (whether for a constant or not), were being moved into some sort of 
> pre-"main" area of code. When stepping through the program, the 
> new/additional assignments to the constant identifiers via constructors don't 
> appear in the places
> they do in the source.
>
> Please pardon me if this is expected behavior, but I just wanted to ask if 
> this was considered normal.
>
> Thank you, Guy.

Hello Guy,

thanks for the bug report and test example.  It is certainly a bug and
is now fixed (about to be git pushed):

$ gm2 constants.mod 
constants.mod:34:14: error: In program module ‘Constants_Example’: cannot 
assign a constant designator ‘Test_Point’ with an expression constructor
   34 |   Test_Point := TPoint{100.0, 80.0};
      |              ^~
constants.mod:62:14: error: cannot assign a constant designator ‘Test_Color’ 
with an expression constructor
   62 |   Test_Color := TColor{0, 0, 0};
      |              ^~

I hope to improve the carot to span the whole line, but will not delay
the immediate fix and will reply to the other questions later on,

regards,
Gaius