Index: libcxx/include/__compare/ordering.h
===================================================================
--- libcxx/include/__compare/ordering.h
+++ libcxx/include/__compare/ordering.h
@@ -40,8 +40,12 @@
 inline constexpr bool __one_of_v = (is_same_v<_Tp, _Args> || ...);
 
 struct _CmpUnspecifiedParam {
-  _LIBCPP_HIDE_FROM_ABI constexpr
-  _CmpUnspecifiedParam(int _CmpUnspecifiedParam::*) noexcept {}
+  _LIBCPP_HIDE_FROM_ABI consteval
+  _CmpUnspecifiedParam(int __literal_zero) noexcept {
+    if (__literal_zero != 0) {
+      __builtin_abort();
+    }
+  }
 
   template<class _Tp, class = enable_if_t<!__one_of_v<_Tp, int, partial_ordering, weak_ordering, strong_ordering>>>
   _CmpUnspecifiedParam(_Tp) = delete;
Index: libcxx/test/std/language.support/cmp/cmp.categories.pre/zero_type.verify.cpp
===================================================================
--- libcxx/test/std/language.support/cmp/cmp.categories.pre/zero_type.verify.cpp
+++ libcxx/test/std/language.support/cmp/cmp.categories.pre/zero_type.verify.cpp
@@ -8,10 +8,6 @@
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 
-// In MSVC mode, there's a slightly different number of errors printed for
-// each of these, so it doesn't add up to the exact expected count of 18.
-// XFAIL: msvc
-
 // <compare>
 
 // Ensure we reject all cases where an argument other than a literal 0 is used
@@ -23,9 +19,7 @@
   void(v op 0L);                                                               \
   void(0L op v);                                                               \
   void(v op nullptr);                                                          \
-  void(nullptr op v);                                                          \
-  void(v op(1 - 1));                                                           \
-  void((1 - 1) op v)
+  void(nullptr op v)
 
 #define TEST_PASS(v, op)                                                       \
   void(v op 0);                                                                \
@@ -33,13 +27,13 @@
 
 template <typename T>
 void test_category(T v) {
-  TEST_FAIL(v, ==);  // expected-error 18 {{}}
-  TEST_FAIL(v, !=);  // expected-error 18 {{}}
-  TEST_FAIL(v, <);   // expected-error 18 {{}}
-  TEST_FAIL(v, <=);  // expected-error 18 {{}}
-  TEST_FAIL(v, >);   // expected-error 18 {{}}
-  TEST_FAIL(v, >=);  // expected-error 18 {{}}
-  TEST_FAIL(v, <=>); // expected-error 18 {{}}
+  TEST_FAIL(v, ==);  // expected-error 12 {{}}
+  TEST_FAIL(v, !=);  // expected-error 12 {{}}
+  TEST_FAIL(v, <);   // expected-error 12 {{}}
+  TEST_FAIL(v, <=);  // expected-error 12 {{}}
+  TEST_FAIL(v, >);   // expected-error 12 {{}}
+  TEST_FAIL(v, >=);  // expected-error 12 {{}}
+  TEST_FAIL(v, <=>); // expected-error 12 {{}}
 
   TEST_PASS(v, ==);
   TEST_PASS(v, !=);
Index: libcxx/test/std/language.support/cmp/cmp.partialord/partialord.pass.cpp
===================================================================
--- libcxx/test/std/language.support/cmp/cmp.partialord/partialord.pass.cpp
+++ libcxx/test/std/language.support/cmp/cmp.partialord/partialord.pass.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
+// ADDITIONAL_COMPILE_FLAGS: -Wzero-as-null-pointer-constant
 
 // <compare>
 
Index: libcxx/test/std/language.support/cmp/cmp.strongord/strongord.pass.cpp
===================================================================
--- libcxx/test/std/language.support/cmp/cmp.strongord/strongord.pass.cpp
+++ libcxx/test/std/language.support/cmp/cmp.strongord/strongord.pass.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
+// ADDITIONAL_COMPILE_FLAGS: -Wzero-as-null-pointer-constant
 
 // <compare>
 
Index: libcxx/test/std/language.support/cmp/cmp.weakord/weakord.pass.cpp
===================================================================
--- libcxx/test/std/language.support/cmp/cmp.weakord/weakord.pass.cpp
+++ libcxx/test/std/language.support/cmp/cmp.weakord/weakord.pass.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
+// ADDITIONAL_COMPILE_FLAGS: -Wzero-as-null-pointer-constant
 
 // <compare>