Make sure cpp_int::eval_convert_to is noexcept as advertised.

Fixes boostorg#553.
tchaikov · May 21, 2023 · d51f2e9 · d51f2e9
1 parent 97b27c4
commit d51f2e9
Showing 1 changed file with 10 additions and 2 deletions.
diff --git a/include/boost/multiprecision/cpp_int/misc.hpp b/include/boost/multiprecision/cpp_int/misc.hpp
@@ -184,7 +184,7 @@ eval_convert_to(R* result, const cpp_int_backend<MinBits1, MaxBits1, SignType1,
 
 template <class R, std::size_t MinBits1, std::size_t MaxBits1, cpp_integer_type SignType1, cpp_int_check_type Checked1, class Allocator1>
 inline BOOST_MP_CXX14_CONSTEXPR typename std::enable_if<std::is_floating_point<R>::value && !is_trivial_cpp_int<cpp_int_backend<MinBits1, MaxBits1, SignType1, Checked1, Allocator1> >::value, void>::type
-eval_convert_to(R* result, const cpp_int_backend<MinBits1, MaxBits1, SignType1, Checked1, Allocator1>& backend) noexcept(boost::multiprecision::detail::is_arithmetic<R>::value)
+eval_convert_to(R* result, const cpp_int_backend<MinBits1, MaxBits1, SignType1, Checked1, Allocator1>& backend) noexcept(boost::multiprecision::detail::is_arithmetic<R>::value && std::numeric_limits<R>::has_infinity)
 {
    BOOST_MP_FLOAT128_USING using std::ldexp;
    if (eval_is_zero(backend))
@@ -244,7 +244,15 @@ eval_convert_to(R* result, const cpp_int_backend<MinBits1, MaxBits1, SignType1,
          if ((eval_lsb_imp(backend) < static_cast<std::size_t>(bits)) || eval_bit_test(backend, static_cast<std::size_t>(bits + 1)))
          {
             #ifdef BOOST_MP_MATH_AVAILABLE
-            *result = boost::math::float_next(*result);
+            BOOST_IF_CONSTEXPR(std::numeric_limits<R>::has_infinity)
+            {
+               // Must NOT throw:
+               *result = boost::math::float_next(*result, boost::math::policies::make_policy(boost::math::policies::overflow_error<boost::math::policies::ignore_error>()));
+            }
+            else
+            {
+               *result = boost::math::float_next(*result);
+            }
             #else
             using std::nextafter; BOOST_MP_FLOAT128_USING
             *result = nextafter(*result, *result * 2);