[Gambas-user] Possible error when doing math on bytes
benoit.minisini at gambas-basic.org
Wed Jan 4 02:17:38 CET 2023
Le 04/01/2023 à 00:16, Brian G a écrit :
> for the last 5 or 6 years we could depend on this, So many of my code in
> many applications is now broken.
> like expecting adding one to 255 to wrap to zero etc...
> This is normal behavior for unsigned numbers.
Actually it's not. All CPU I know behave like this, but the C standard
explicitely says that overflow leads to undefined results. Nobody must
rely on that.
I had five places in all Gambas code I wrote (for my job and for Gambas)
that incorrectly used overflow. It took a few minutes to fix all of them.
I don't understand how you can rely so heavily on overflow with bytes...
> I am going to have to waste months fixing and checking production
> For me this is almost enough reason to stop using gambas altogether.
> I am extremely, extremely upset.... we are talking real production software
> It all has to be reevaluated and tested this is man months of testing and
> I just can not afford nor can my clients afford such expense.
> This is a very bad thing.
> Can an option be added to just turn this off, please, begging, go back
> to old behaviors
I won't go back the old behaviour which is incorrect by the definition
of the C standard, and lead to a lot of invisible bugs and security
breach in software.
I will think about how I can add an option for allowing the old
incorrect behaviour, but after the release of Gambas 3.18.0. At the
moment I don't know how I can do that.
You will have to wait a little before using Gambas 3.18 in production.
Sorry for the inconvenience.
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