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Merge pull request #881 from robert-andrzejuk/patch-1

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Refactor `narrow`.
This commit is contained in:
Jordan Maples [MSFT] 2020-08-05 15:16:25 -07:00 committed by GitHub
commit 552eedb390
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1 changed files with 10 additions and 12 deletions
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22
include/gsl/gsl_util
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@ -90,15 +90,6 @@ struct narrowing_error : public std::exception
{
};
namespace details
{
template <class T, class U>
struct is_same_signedness
: public std::integral_constant<bool, std::is_signed<T>::value == std::is_signed<U>::value>
{
};
} // namespace details
// narrow() : a checked version of narrow_cast() that throws if the cast changed the value
template <class T, class U>
GSL_SUPPRESS(type.1) // NO-FORMAT: attribute
@ -106,10 +97,17 @@ GSL_SUPPRESS(f.6) // NO-FORMAT: attribute // TODO: MSVC /analyze does not recogn
constexpr
T narrow(U u) noexcept(false)
{
T t = narrow_cast<T>(u);
if (static_cast<U>(t) != u) throw narrowing_error{};
if (!details::is_same_signedness<T, U>::value && ((t < T{}) != (u < U{})))
constexpr const bool is_different_signedness = (std::is_signed<T>::value != std::is_signed<U>::value);
const T t = narrow_cast<T>(u);
if (static_cast<U>(t) != u
|| (is_different_signedness
&& ((t < T{}) != (u < U{}))))
{
throw narrowing_error{};
}
return t;
}