libstdc++: Fix _GLIBCXX_DEBUG mode constexpr compatibility

The __glibcxx_check_can_[increment|decrement]_range macros are using the
_GLIBCXX_DEBUG_VERIFY_COND_AT macro which is not constexpr compliant and will produce nasty
diagnostics rather than the std::__failed_assertion dedicated to constexpr. Replace it with
correct _GLIBCXX_DEBUG_VERIFY_AT_F.

libstdc++-v3/ChangeLog:

	* include/debug/macros.h (__glibcxx_check_can_increment_range): Replace
	_GLIBCXX_DEBUG_VERIFY_COND_AT usage with _GLIBCXX_DEBUG_VERIFY_AT_F.
	(__glibcxx_check_can_decrement_range): Likewise.
	* testsuite/25_algorithms/copy_backward/constexpr.cc (test03): New.
	* testsuite/25_algorithms/copy/debug/constexpr_neg.cc: New test.
	* testsuite/25_algorithms/copy_backward/debug/constexpr_neg.cc: New test.
	* testsuite/25_algorithms/equal/constexpr_neg.cc: New test.
	* testsuite/25_algorithms/equal/debug/constexpr_neg.cc: New test.

6 files changed, 210 insertions, 4 deletions

diff --git a/libstdc++-v3/include/debug/macros.h b/libstdc++-v3/include/debug/macros.h
index ef4c76c..a69310d 100644
--- a/libstdc++-v3/include/debug/macros.h
+++ b/libstdc++-v3/include/debug/macros.h
@@ -98,13 +98,13 @@ _GLIBCXX_DEBUG_VERIFY(__gnu_debug::__can_advance(_First, _Size),	\
   do									\
   {									\
     typename __gnu_debug::_Distance_traits<__decltype(_First1)>::__type __dist;\
-    _GLIBCXX_DEBUG_VERIFY_COND_AT(					\
+    _GLIBCXX_DEBUG_VERIFY_AT_F(						\
 			__gnu_debug::__valid_range(_First1, _Last1, __dist),\
 			_M_message(__gnu_debug::__msg_valid_range)	\
 			._M_iterator(_First1, #_First1)			\
 			._M_iterator(_Last1, #_Last1),			\
 			__FILE__,__LINE__,__PRETTY_FUNCTION__);		\
-    _GLIBCXX_DEBUG_VERIFY_COND_AT(					\
+    _GLIBCXX_DEBUG_VERIFY_AT_F(						\
 			__gnu_debug::__can_advance(_First2, __dist.first),\
 			_M_message(__gnu_debug::__msg_iter_subscript_oob)\
 			._M_iterator(_First2, #_First2)			\
@@ -116,13 +116,13 @@ _GLIBCXX_DEBUG_VERIFY(__gnu_debug::__can_advance(_First, _Size),	\
   do									\
   {									\
     typename __gnu_debug::_Distance_traits<__decltype(_First1)>::__type __dist;\
-    _GLIBCXX_DEBUG_VERIFY_COND_AT(					\
+    _GLIBCXX_DEBUG_VERIFY_AT_F(						\
 			__gnu_debug::__valid_range(_First1, _Last1, __dist),\
 			_M_message(__gnu_debug::__msg_valid_range)	\
 			._M_iterator(_First1, #_First1)			\
 			._M_iterator(_Last1, #_Last1),			\
 			__FILE__,__LINE__,__PRETTY_FUNCTION__);		\
-    _GLIBCXX_DEBUG_VERIFY_COND_AT(					\
+    _GLIBCXX_DEBUG_VERIFY_AT_F(						\
 			__gnu_debug::__can_advance(_First2, -__dist.first),\
 			_M_message(__gnu_debug::__msg_iter_subscript_oob)\
 			._M_iterator(_First2, #_First2)			\
diff --git a/libstdc++-v3/testsuite/25_algorithms/copy/debug/constexpr_neg.cc b/libstdc++-v3/testsuite/25_algorithms/copy/debug/constexpr_neg.cc
new file mode 100644
index 0000000..fc66a2f
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/copy/debug/constexpr_neg.cc
@@ -0,0 +1,53 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a xfail *-*-* } }
+// { dg-require-debug-mode ""  }
+
+#include <algorithm>
+#include <array>
+
+constexpr bool
+test1()
+{
+  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
+  std::array<int, 12> ma0{{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}};
+
+  const auto out6 = std::copy(ca0.begin() + 8, ca0.begin(), ma0.begin() + 2);
+
+  return out6 == ma0.begin() + 10;
+}
+
+static_assert(test1()); // { dg-error "non-constant condition" }
+
+constexpr bool
+test2()
+{
+  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
+  std::array<int, 12> ma0{{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}};
+
+  const auto out6 = std::copy(ca0.begin(), ca0.begin() + 8, ma0.begin() + 10);
+
+  return out6 == ma0.begin() + 18;
+}
+
+static_assert(test2()); // { dg-error "is outside the bounds" }
+
+// { dg-prune-output "in 'constexpr' expansion" }
+// { dg-prune-output "failed_assertion" }
+// { dg-prune-output "non-constant condition" }
diff --git a/libstdc++-v3/testsuite/25_algorithms/copy_backward/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/copy_backward/constexpr.cc
index e97e30e..b98cb0d 100644
--- a/libstdc++-v3/testsuite/25_algorithms/copy_backward/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/copy_backward/constexpr.cc
@@ -52,3 +52,15 @@ test02()
 }
 
 static_assert(test02());
+
+constexpr bool
+test03()
+{
+  std::array<int, 12> ma0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
+  const auto out7 = std::copy_backward(ma0.begin(), ma0.begin() + 8,
+				       ma0.begin() + 10);
+
+  return out7 == ma0.begin() + 2 && *out7 == 0 && *(ma0.begin() + 9) == 7;
+}
+
+static_assert(test03());
diff --git a/libstdc++-v3/testsuite/25_algorithms/copy_backward/debug/constexpr_neg.cc b/libstdc++-v3/testsuite/25_algorithms/copy_backward/debug/constexpr_neg.cc
new file mode 100644
index 0000000..6e2dc2f
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/copy_backward/debug/constexpr_neg.cc
@@ -0,0 +1,40 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a xfail *-*-* } }
+// { dg-require-debug-mode ""  }
+
+#include <algorithm>
+#include <array>
+
+constexpr bool
+test()
+{
+  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
+  std::array<int, 12> ma0{{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}};
+
+  const auto out7 = std::copy_backward(ca0.begin() + 8, ca0.begin(),
+				       ma0.begin() + 10);
+
+  return true;
+}
+
+static_assert(test()); // { dg-error "non-constant condition" }
+
+// { dg-prune-output "in 'constexpr' expansion" }
+// { dg-prune-output "failed_assertion" }
diff --git a/libstdc++-v3/testsuite/25_algorithms/equal/constexpr_neg.cc b/libstdc++-v3/testsuite/25_algorithms/equal/constexpr_neg.cc
new file mode 100644
index 0000000..206c1cf
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/equal/constexpr_neg.cc
@@ -0,0 +1,50 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a xfail *-*-* } }
+// { dg-require-normal-mode "" }
+
+#include <algorithm>
+#include <array>
+
+constexpr bool
+test01()
+{
+  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
+  constexpr std::array<int, 12> ca1{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
+
+  const auto outa = std::equal(ca0.end(), ca0.begin(), ca1.begin());
+  return outa;
+}
+
+static_assert(test01()); // { dg-error "outside the bounds" }
+
+constexpr bool
+test02()
+{
+  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
+  constexpr std::array<int, 11> ca1{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}};
+
+  const auto outa = std::equal(ca0.begin(), ca0.end(), ca1.begin());
+  return outa;
+}
+
+static_assert(test02()); // { dg-error "outside the bounds" }
+
+// { dg-prune-output "non-constant condition" }
+// { dg-prune-output "in 'constexpr'" }
diff --git a/libstdc++-v3/testsuite/25_algorithms/equal/debug/constexpr_neg.cc b/libstdc++-v3/testsuite/25_algorithms/equal/debug/constexpr_neg.cc
new file mode 100644
index 0000000..3a6903c
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/equal/debug/constexpr_neg.cc
@@ -0,0 +1,51 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a xfail *-*-* } }
+// { dg-require-debug-mode "" }
+
+#include <algorithm>
+#include <array>
+
+constexpr bool
+test01()
+{
+  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
+  constexpr std::array<int, 12> ca1{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
+
+  const auto outa = std::equal(ca0.end(), ca0.begin(), ca1.begin());
+  return outa;
+}
+
+static_assert(test01()); // { dg-error }
+
+constexpr bool
+test02()
+{
+  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
+  constexpr std::array<int, 11> ca1{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}};
+
+  const auto outa = std::equal(ca0.begin(), ca0.end(), ca1.begin());
+  return outa;
+}
+
+static_assert(test02()); // { dg-error "outside the bounds" }
+
+// { dg-prune-output "non-constant condition" }
+// { dg-prune-output "in 'constexpr'" }
+// { dg-prune-output "failed_assertion" }