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Do the math in uniform_int_distribution::operator() as unsigned to prevent UB when overflowing. Also add a UBSAN notification that we're ffine with unsigned overflow. This fixes PR#32617. Thanks to Vincent & Christoph for their help with this issue. 

llvm-svn: 343996
This commit is contained in:
Marshall Clow 2018-10-08 20:20:34 +00:00
parent ff9f02580d
commit 2dd5335204
1 changed files with 3 additions and 2 deletions
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5
libcxx/include/algorithm
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@ -2899,10 +2899,11 @@ template<class _IntType>
template<class _URNG>
typename uniform_int_distribution<_IntType>::result_type
uniform_int_distribution<_IntType>::operator()(_URNG& __g, const param_type& __p)
_LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
{
typedef typename conditional<sizeof(result_type) <= sizeof(uint32_t),
uint32_t, uint64_t>::type _UIntType;
const _UIntType _Rp = __p.b() - __p.a() + _UIntType(1);
const _UIntType _Rp = _UIntType(__p.b()) - _UIntType(__p.a()) + _UIntType(1);
if (_Rp == 1)
return __p.a();
const size_t _Dt = numeric_limits<_UIntType>::digits;
@ -2989,7 +2990,7 @@ random_shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last,
{
difference_type __i = __rand(__d);
if (__i != difference_type(0))
swap(*__first, *(__first + __i));
swap(*__first, *(__first + __i));
}
}
}