LineageOS/android_external_libcxx
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Make lcm/gcd work better in edge cases. Fixes a UBSAN failure.

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git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@294779 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Marshall Clow
2017-02-10 20:49:08 +00:00
parent 00d9a944af
commit ebf66a385f
6 changed files with 52 additions and 28 deletions
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27
include/experimental/numeric
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@@ -45,18 +45,23 @@ inline namespace fundamentals_v2 {
_LIBCPP_BEGIN_NAMESPACE_LFTS_V2
template <typename _Tp, bool _IsSigned = is_signed<_Tp>::value> struct __abs;
template <typename _Result, typename _Source, bool _IsSigned = is_signed<_Source>::value> struct __abs;
template <typename _Tp>
struct __abs<_Tp, true> {
template <typename _Result, typename _Source>
struct __abs<_Result, _Source, true> {
_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
_Tp operator()(_Tp __t) const noexcept { return __t >= 0 ? __t : -__t; }
_Result operator()(_Source __t) const noexcept
{
if (__t >= 0) return __t;
if (__t == numeric_limits<_Source>::min()) return -static_cast<_Result>(__t);
return -__t;
}
};
template <typename _Tp>
struct __abs<_Tp, false> {
template <typename _Result, typename _Source>
struct __abs<_Result, _Source, false> {
_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
_Tp operator()(_Tp __t) const noexcept { return __t; }
_Result operator()(_Source __t) const noexcept { return __t; }
};
@@ -79,8 +84,8 @@ gcd(_Tp __m, _Up __n)
static_assert((!is_same<typename remove_cv<_Up>::type, bool>::value), "Second argument to gcd cannot be bool" );
using _Rp = common_type_t<_Tp,_Up>;
using _Wp = make_unsigned_t<_Rp>;
return static_cast<_Rp>(__gcd(static_cast<_Wp>(__abs<_Tp>()(__m)),
static_cast<_Wp>(__abs<_Up>()(__n))));
return static_cast<_Rp>(__gcd(static_cast<_Wp>(__abs<_Rp, _Tp>()(__m)),
static_cast<_Wp>(__abs<_Rp, _Up>()(__n))));
}
template<class _Tp, class _Up>
@@ -95,8 +100,8 @@ lcm(_Tp __m, _Up __n)
return 0;
using _Rp = common_type_t<_Tp,_Up>;
_Rp __val1 = __abs<_Tp>()(__m) / gcd(__m,__n);
_Up __val2 = __abs<_Up>()(__n);
_Rp __val1 = __abs<_Rp, _Tp>()(__m) / gcd(__m, __n);
_Rp __val2 = __abs<_Rp, _Up>()(__n);
_LIBCPP_ASSERT((numeric_limits<_Rp>::max() / __val1 > __val2), "Overflow in lcm");
return __val1 * __val2;
}