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
diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index c5c1729..9ce6aa0 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -2899,10 +2899,11 @@
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 @@
{
difference_type __i = __rand(__d);
if (__i != difference_type(0))
- swap(*__first, *(__first + __i));
+ swap(*__first, *(__first + __i));
}
}
}
