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Subject: Re: [boost] [optional] operator<(optional<T>, T) -- is it wrong?
From: Stephan T. Lavavej (stl_at_[hidden])
Date: 2014-12-02 15:27:36

[Niall Douglas]
> BTW I think MSVC/Dinkumware *has* fixed their std::hash<>, theirs is
> several orders of magntitude more complex than the trivial hash
> libstdc++ uses. Indeed this leads to MSVC's apparent poor
> unordered_map performance when compared to GCC (about a 12-40%
> performance loss).
> Stephan can probably confirm or refute this claim of MSVC/Dinkumware
> having a safe hash though. It may just be he uses a well distributed
> hash instead of a trivial hash, not one cryptographically safe.

VC currently uses FNV-1a for everything. This is good at jumbling up bits, and pretty fast (although not as fast as returning an integer unchanged), but it is absolutely not cryptographically secure, nor does it attempt to resist collisions triggered by an intelligent adversary.

We reserve the right to change our hash implementation in the future.


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