danalbert added inline comments.
================
Comment at: include/__hash_table:2141
__n = 2;
else if (__n & (__n - 1))
__n = __next_prime(__n);
----------------
mclow.lists wrote:
> danalbert wrote:
> > With `rehash(0)` this is `0 & (0 - 1)`, which triggers
> > unsigned-integer-overflow.
> Grumble, grumble. That's not UB, that's just UBSan whining.
> On the other hand, this doesn't appear to change any behavior, and shuts
> UBSan up.
FWIW, this check isn't enabled in ubsan by default. Android uses it for testing
and mititgation in a handful of projects because it does catch errors
(stagefright was an unsigned overflow issue). It's good to keep the libc++
headers clean of these issues so we're not dictating the compile flags of
libc++ users.
Repository:
rCXX libc++
https://reviews.llvm.org/D40743
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