Implement LWG-2381 Inconsistency in parsing floating point numbers

stl/inc/xlocmon

@@ -364,7 +364,7 @@ protected:
  const char* _Eb = _Str.c_str();
  char* _Ep;
  int _Errno = 0;
- const long double _Ans = _Stodx_v2(_Eb, &_Ep, 0, &_Errno); // convert and "widen" double to long double
+ const long double _Ans = _Stodx_v3(_Eb, &_Ep, &_Errno); // convert and "widen" double to long double
 
  if (_Ep == _Eb || _Errno != 0) {
  _State |= ios_base::failbit;

tests/libcxx/expected_results.txt

@@ -121,6 +121,10 @@ std/language.support/support.limits/support.limits.general/ranges.version.compil
 # libc++ is missing various <format> DRs
 std/language.support/support.limits/support.limits.general/format.version.compile.pass.cpp FAIL
 
+# libc++ doesn't implement LWG-2381
+std/localization/locale.categories/category.numeric/locale.num.get/facet.num.get.members/get_double.pass.cpp FAIL
+std/localization/locale.categories/category.numeric/locale.num.get/facet.num.get.members/get_float.pass.cpp FAIL
+
 # libc++ doesn't implement LWG-3670
 std/ranges/range.factories/range.iota.view/iterator/member_typedefs.compile.pass.cpp FAIL
 
@@ -444,11 +448,6 @@ std/containers/sequences/array/array.swap/swap.fail.cpp FAIL
 std/algorithms/alg.sorting/alg.merge/inplace_merge_comp.pass.cpp FAIL
 std/algorithms/alg.sorting/alg.min.max/minmax_init_list_comp.pass.cpp FAIL
 
-# GH-1259 <locale>: wrong field extraction for hexfloats, or special cases like inf
-std/localization/locale.categories/category.numeric/locale.num.get/facet.num.get.members/get_double.pass.cpp FAIL
-std/localization/locale.categories/category.numeric/locale.num.get/facet.num.get.members/get_float.pass.cpp FAIL
-std/localization/locale.categories/category.numeric/locale.num.get/facet.num.get.members/get_long_double.pass.cpp FAIL
-
 # GH-1277 <xlocnum>: We don't match numpunct groups correctly in do_get
 std/localization/locale.categories/category.numeric/locale.num.get/facet.num.get.members/get_long.pass.cpp FAIL
 
@@ -674,6 +673,9 @@ std/time/time.clock/time.clock.file/to_from_sys.pass.cpp FAIL
 # libc++'s filesystem::path::iterator models bidirectional_iterator, which is not guaranteed by the Standard
 std/input.output/filesystems/class.path/range_concept_conformance.compile.pass.cpp FAIL
 
+# libc++ assumes long double is at least 80-bit; also affected by LWG-2381
+std/localization/locale.categories/category.numeric/locale.num.get/facet.num.get.members/get_long_double.pass.cpp FAIL
+
 # MaybePOCCAAllocator doesn't meet the allocator requirements
 std/containers/sequences/vector/vector.cons/assign_copy.pass.cpp FAIL
 

tests/std/test.lst

@@ -221,6 +221,7 @@ tests\GH_003105_piecewise_densities
 tests\GH_003119_error_category_ctor
 tests\GH_003246_cmath_narrowing
 tests\GH_003617_vectorized_meow_element
+tests\LWG2381_num_get_floating_point
 tests\LWG2597_complex_branch_cut
 tests\LWG3018_shared_ptr_function
 tests\LWG3121_constrained_tuple_forwarding_ctor

tests/std/tests/LWG2381_num_get_floating_point/env.lst

@@ -0,0 +1,4 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+RUNALL_INCLUDE ..\usual_matrix.lst