From 6b03a1b42352e38fafff67c6d8d685144b8f9a4c Mon Sep 17 00:00:00 2001
From: Marshall Clow <mclow.lists@gmail.com>
Date: Wed, 29 May 2019 15:17:55 +0000
Subject: [PATCH] Add additional constraints on midpoint(pointer, pointer).
 Fixes PR#42037.

llvm-svn: 361970
---
 libcxx/include/numeric                                    |  7 +++++--
 .../numeric.ops/numeric.ops.midpoint/midpoint.fail.cpp    | 15 ++++++++++++---
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/libcxx/include/numeric b/libcxx/include/numeric
index 4b08611..62cc29c 100644
--- a/libcxx/include/numeric
+++ b/libcxx/include/numeric
@@ -527,7 +527,7 @@ lcm(_Tp __m, _Up __n)
 #if _LIBCPP_STD_VER > 17
 template <class _Tp>
 _LIBCPP_INLINE_VISIBILITY constexpr
-enable_if_t<is_integral_v<_Tp> && !is_same_v<bool, _Tp>, _Tp>
+enable_if_t<is_integral_v<_Tp> && !is_same_v<bool, _Tp> && !is_null_pointer_v<_Tp>, _Tp>
 midpoint(_Tp __a, _Tp __b) noexcept
 _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
 {
@@ -548,7 +548,10 @@ _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
 
 template <class _TPtr>
 _LIBCPP_INLINE_VISIBILITY constexpr
-enable_if_t<is_pointer_v<_TPtr>, _TPtr>
+enable_if_t<is_pointer_v<_TPtr> 
+             && is_object_v<remove_pointer_t<_TPtr>> 
+             && ! is_void_v<remove_pointer_t<_TPtr>> 
+             && (sizeof(remove_pointer_t<_TPtr>) > 0), _TPtr>
 midpoint(_TPtr __a, _TPtr __b) noexcept
 {
     return __a + _VSTD::midpoint(ptrdiff_t(0), __b - __a);
diff --git a/libcxx/test/std/numerics/numeric.ops/numeric.ops.midpoint/midpoint.fail.cpp b/libcxx/test/std/numerics/numeric.ops/numeric.ops.midpoint/midpoint.fail.cpp
index 2352ce7..c757610 100644
--- a/libcxx/test/std/numerics/numeric.ops/numeric.ops.midpoint/midpoint.fail.cpp
+++ b/libcxx/test/std/numerics/numeric.ops/numeric.ops.midpoint/midpoint.fail.cpp
@@ -18,13 +18,22 @@
 
 #include "test_macros.h"
 
+int func1 () { return 1; }
+int func2 () { return 2; }
+
+struct Incomplete;
+Incomplete *ip = nullptr;
+void       *vp = nullptr;
+
 int main(int, char**)
 {
-    (void) std::midpoint(false, true); // expected-error {{no matching function for call to 'midpoint'}}
+    (void) std::midpoint(false, true);  // expected-error {{no matching function for call to 'midpoint'}}
 
 //  A couple of odd pointer types that should fail
-    (void) std::midpoint(nullptr, nullptr);     // expected-error {{no matching function for call to 'midpoint'}}
-    (void) std::midpoint((void *)0, (void *)0); // expected-error@numeric:* {{arithmetic on pointers to void}}
+    (void) std::midpoint(nullptr, nullptr);  // expected-error {{no matching function for call to 'midpoint'}}
+    (void) std::midpoint(func1, func2);      // expected-error {{no matching function for call to 'midpoint'}}
+    (void) std::midpoint(ip, ip);            // expected-error {{no matching function for call to 'midpoint'}}
+    (void) std::midpoint(vp, vp);            // expected-error {{no matching function for call to 'midpoint'}}
     
     return 0;
 }
-- 
2.7.4