Message 87712 - Python tracker

Message87712

Author	loewis
Recipients	alexandre.vassalotti, christian.heimes, donmez, gregory.p.smith, gvanrossum, loewis, mark.dickinson, matejcik, nnorwitz, pitrou, vstinner
Date	2009-05-13.21:32:40
SpamBayes Score	2.7537398e-08
Marked as misclassified	No
Message-id	<4A0B3C75.3040104@v.loewis.de>
In-reply-to	<1242248309.07.0.900383605185.issue1621@psf.upfronthosting.co.za>

Content
> size = Py_SIZE(a) * n; > > The multiplication should be safe from overflow, and I don't get > any warning at all either with this rewrite (using -O3 -Wall -Wextra - > Wsigned-overflow=5) or from the original code, so there's nothing to > silence. This is puzzling, isn't it? It could overflow, could it not? >> I think there is a second solution: perform the multiplication >> unsigned in the first place. > > That would work too. I find the above code clearer, though. I agree in this case. In general, I'm not convinced that it is always possible to rewrite the code in that way conveniently.

Content

> 	size = Py_SIZE(a) * n;
> 
> The multiplication should be safe from overflow, and I don't get
> any warning at all either with this rewrite (using -O3 -Wall -Wextra -
> Wsigned-overflow=5) or from the original code, so there's nothing to 
> silence.

This is puzzling, isn't it? It *could* overflow, could it not?

>> I think there is a second solution: perform the multiplication
>> unsigned in the first place.
> 
> That would work too.  I find the above code clearer, though.

I agree in this case. In general, I'm not convinced that it
is always possible to rewrite the code in that way conveniently.

History
Date	User	Action	Args
2009-05-13 21:32:42	loewis	set	recipients: + loewis, gvanrossum, nnorwitz, gregory.p.smith, mark.dickinson, pitrou, vstinner, christian.heimes, alexandre.vassalotti, donmez, matejcik
2009-05-13 21:32:41	loewis	link	issue1621 messages
2009-05-13 21:32:40	loewis	create