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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug libstdc++/100444] std::random_device isn't random on AMD
Date: Thu, 06 May 2021 10:05:38 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100444

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #4)
> Thus I believe the issue is mitigated at the kernel level and people that

Yes, that's my understanding.

> cannot be bothered to update their ucode or the kernel are not likely
> bothered to update libstdc++ either.  Note handling it above would
> raise a runtime error rather than falling back to other sources of
> randomness.
> Doing the checking where we detect rdrand support would avoid that.

I suppose we could use the rdrand instruction a couple of times when doing =
the
cpuid support, and if it gives the same value conclude it's broken and so n=
ot
available.

But as you say, people who haven't bothered to update microcode probably ar=
en't
going to get a libstdc++ update either.=