[fpc-devel] [Patch/RFC] Warnings for (in/over)complete case statements

[Jonas Maebe]

On 12/05/2019 19:39, Ondrej Pokorny wrote:
> On 12.05.2019 18:56, Jonas Maebe wrote:
>> As far as range checking and undefined behaviour is concerned, they 
>> do. I.e., you won't get undefined behaviour by assigning any value 
>> between low(enum)..high(enum) to them.
> 
> Very good, thank you. IMO this should be clearly documented to avoid 
> confusion.

True.

> And if they are valid they should not cause any runtime errors:
> 
> program Project1;
> {$mode objfpc}
> type
>    TMyEnum = (two=2, five=5);
> var
>    E: TMyEnum;
> begin
>    E := TMyEnum(3);
>    Writeln(E); // RunError (107)
> end.
> 
> (From the above example one would say they are not valid.)

write(enum) is an FPC extension. It writes out the declared enum 
identifier. There is none in this case, so a run time error is appropriate.

> There was a misunderstanding. I thought you meant with "implicit" values 
> the "implicit default values" (=0):
> 
> program Project1;
> {$mode objfpc}
> type
>    TMyEnum = (two=2, five=5);
>    TMyObject = class
>      E: TMyEnum;
>    end;
> var
>    O: TMyObject;
> begin
>    O := TMyObject.Create;
>    Writeln(Ord(O.E)); // R has an implicit default valuethat is invalid
>    ReadLn;
> end.
> 
> But you meant the implicit valid values (the holes). Now it's clear.

Ah, indeed.


Jonas