Re: gm2 rejecting a constant statement as variable

[Gaius Mulley]

Alice Osako <alicetrillianosako@gmail.com> writes:

> I ran into another issue which I am less certain about. The following 
> declaration
>
> VAR
>   powerOf2 : ARRAY [0..Bitwidth-1] OF CARDINAL;
>
> Gives the following error:
>
> src/imp/CardMath.mod:374:14: error: In procedure ‘IntMaxDecDigitsTable’: 
> circular dependency error found when trying to resolve array
>   374 |   powerOf2 : ARRAY [0..Bitwidth-1] OF CARDINAL;
>       |              ^~~~~
>
> What is peculiar here is that a) the declarations of powerOf2 and Bitwidth 
> are not circular, and b) this declaration is of module scope, and comes 
> before the
> beginning of IntMaxDecDigitsTable. For reference, Bitwidth is a constant 
> defined as
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   MaxCardDivPow2Of8   = MAX(CARDINAL) DIV 256;
>   MaxCardDivPow2Of16  = MaxCardDivPow2Of8 DIV 256;
>   MaxCardDivPow2Of24  = MaxCardDivPow2Of16 DIV 256;
>   MaxCardDivPow2Of32  = MaxCardDivPow2Of24 DIV 256;
>   MaxCardDivPow2Of40  = MaxCardDivPow2Of32 DIV 256;
>   MaxCardDivPow2Of48  = MaxCardDivPow2Of40 DIV 256;
>   MaxCardDivPow2Of56  = MaxCardDivPow2Of48 DIV 256;
>   MaxCardDivPow2Of64  = MaxCardDivPow2Of56 DIV 256;
>   MaxCardDivPow2Of72  = MaxCardDivPow2Of64 DIV 256;
>   MaxCardDivPow2Of80  = MaxCardDivPow2Of72 DIV 256;
>   MaxCardDivPow2Of88  = MaxCardDivPow2Of80 DIV 256;
>   MaxCardDivPow2Of96  = MaxCardDivPow2Of88 DIV 256;
>   MaxCardDivPow2Of104 = MaxCardDivPow2Of96 DIV 256;
>   MaxCardDivPow2Of112 = MaxCardDivPow2Of104 DIV 256;
>   MaxCardDivPow2Of120 = MaxCardDivPow2Of112 DIV 256;
>
>   BW8   = (MAX(CARDINAL) <= 255);
>   BW16  = (MaxCardDivPow2Of8 > 0) AND (MaxCardDivPow2Of8 <= 255);
>   BW24  = (MaxCardDivPow2Of16 > 0) AND (MaxCardDivPow2Of16 <= 255);
>   BW32  = (MaxCardDivPow2Of24 > 0) AND (MaxCardDivPow2Of24 <= 255);
>   BW40  = (MaxCardDivPow2Of32 > 0) AND (MaxCardDivPow2Of32 <= 255);
>   BW48  = (MaxCardDivPow2Of40 > 0) AND (MaxCardDivPow2Of40 <= 255);
>   BW56  = (MaxCardDivPow2Of48 > 0) AND (MaxCardDivPow2Of48 <= 255);
>   BW64  = (MaxCardDivPow2Of56 > 0) AND (MaxCardDivPow2Of56 <= 255);
>   BW72  = (MaxCardDivPow2Of64 > 0) AND (MaxCardDivPow2Of64 <= 255);
>   BW80  = (MaxCardDivPow2Of72 > 0) AND (MaxCardDivPow2Of72 <= 255);
>   BW88  = (MaxCardDivPow2Of80 > 0) AND (MaxCardDivPow2Of80 <= 255);
>   BW96  = (MaxCardDivPow2Of88 > 0) AND (MaxCardDivPow2Of88 <= 255);
>   BW104 = (MaxCardDivPow2Of96 > 0) AND (MaxCardDivPow2Of96 <= 255);
>   BW112 = (MaxCardDivPow2Of104 > 0) AND (MaxCardDivPow2Of104 <= 255);
>   BW120 = (MaxCardDivPow2Of112 > 0) AND (MaxCardDivPow2Of112 <= 255);
>   BW128 = (MaxCardDivPow2Of120 > 0) AND (MaxCardDivPow2Of120 <= 255);
>
>   Bitwidth =
>     8*ORD(BW8) + 16*ORD(BW16) + 24*ORD(BW24) + 32*ORD(BW32) +
>     40*ORD(BW40) + 48*ORD(BW48) + 56*ORD(BW56) + 64*ORD(BW64) +
>     72*ORD(BW72) + 80*ORD(BW80) + 88*ORD(BW88) + 96*ORD(BW96) +
>     104*ORD(BW104) + 112*ORD(BW112) + 120*ORD(BW120) + 128*ORD(BW128);
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> where BWn is a series of boolean values which gate individual bit markers 
> (AFAICT, anyway). 
>
> I can't see how these declarations would be circular.

I suspect this bug will disappear once the constant expression relop bug
has been fixed (or is related).  Currently the compiler is creating a
temporary variable to store the result of the relop (which it thinks
will be known at runtime) - but this conflicts with the declaration of
the array needed at compiletime.