[openssl-dev] [openssl.org #4362] chacha-x86.pl has stricter aliasing requirements than other files

Andy Polyakov appro at openssl.org
Fri Mar 4 14:26:11 UTC 2016

>> Fear is irrational and destructive feeling. Having faith that world is
>> better than that it nothing but healthy :-) What I'm saying is that
>> let's put a little bit more substance into discourse. Would anybody
>> consider it *sane* programming practice to rely on partially overlapping
>> buffers in *general* case? I.e. without actually *knowing* (as opposite
>> to *assuming*) what's gong on? [Control question: does compiler
>> guarantee order of references to memory?] As said in last message I
>> don't consider it sane and even consider it natural [which means that
>> I'd expect majority to not consider it sane too].
> One the cool features of the OCB code some folks I know to be using
> and relying on is that it supports in-place encryption.  You give
> it a buffer, and it is encrypted in place.  This is specifically
> promised by the API and is noticeably fast.
> No idea whether this is a useful datapoint...

Question if specifically about *partially* overlapping buffers. Or in
other words it's not a question whether or not *fully* overlapping
buffers, a.k.a. in-place processing, should be supported (they should)
or may be used (they may).

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