[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [ft-devel] those OVERFLOW_* macros and Fontval b69 (Re: Freetype-dev

From: Markus Trippelsdorf
Subject: Re: [ft-devel] those OVERFLOW_* macros and Fontval b69 (Re: Freetype-devel Digest, Vol 149, Issue 5
Date: Mon, 5 Jun 2017 07:27:47 +0200

On 2017.06.05 at 05:56 +0200, Werner LEMBERG wrote:
> >> Ditto for bytecode.  Checking every addition, subtraction or
> >> multiplication for overflow is something I want to avoid,
> > 
> > Of course, I am only suggesting rejecting input with unreasonably
> > large coordinates or metric values.
> This would be ideal, yes, but I don't see how you can do that.  For
> example, it makes sense to reject, say, PCF properties that exceed the
> value 0x7FFF (I added such tests recently).  Similar things can be
> done for other format too.  However, the majority of input data in
> most formats are deltas, and here you would have to check after every
> addition, subtraction, or multiplication whether you get something
> `unreasonable'.

BTW are you aware of gcc's and clang's built-in functions that perform
arithmetic with overflow checking? Maybe they could help.


reply via email to

[Prev in Thread] Current Thread [Next in Thread]