From 8c84486bba104399b7e544cb1ba343646d39ea0a Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Thu, 29 Oct 2020 14:47:18 +0000
Subject: [PATCH] libstdc++: Improve tests for constexpr algorithms

These tests just return true without checking that the results of the
algorithms. Although it should be safe to assume that the algorithms
behave the same at compile-time as at run-time, we can use these tests
to verify it.

This replaces each 'return true' statement with a condition that depends
on the basic functionality of the algorithm, such as returning an
iterator to the right position.

libstdc++-v3/ChangeLog:

	* testsuite/25_algorithms/all_of/constexpr.cc: Check result of
	the algorithm.
	* testsuite/25_algorithms/any_of/constexpr.cc: Likewise.
	* testsuite/25_algorithms/binary_search/constexpr.cc: Likewise.
	* testsuite/25_algorithms/copy_backward/constexpr.cc: Likewise.
	* testsuite/25_algorithms/count/constexpr.cc: Likewise.
	* testsuite/25_algorithms/equal/constexpr.cc: Likewise.
	* testsuite/25_algorithms/equal_range/constexpr.cc: Likewise.
	* testsuite/25_algorithms/fill/constexpr.cc: Likewise.
	* testsuite/25_algorithms/find_end/constexpr.cc: Likewise.
	* testsuite/25_algorithms/find_if/constexpr.cc: Likewise.
	* testsuite/25_algorithms/is_partitioned/constexpr.cc: Likewise.
	* testsuite/25_algorithms/is_permutation/constexpr.cc: Likewise.
	* testsuite/25_algorithms/is_sorted_until/constexpr.cc:
	Likewise.
	* testsuite/25_algorithms/lexicographical_compare/constexpr.cc:
	Likewise.
	* testsuite/25_algorithms/lower_bound/constexpr.cc: Likewise.
	* testsuite/25_algorithms/merge/constexpr.cc: Likewise.
	* testsuite/25_algorithms/mismatch/constexpr.cc: Likewise.
	* testsuite/25_algorithms/none_of/constexpr.cc: Likewise.
	* testsuite/25_algorithms/partition_copy/constexpr.cc: Likewise.
	* testsuite/25_algorithms/remove_copy/constexpr.cc: Likewise.
	* testsuite/25_algorithms/remove_copy_if/constexpr.cc: Likewise.
	* testsuite/25_algorithms/remove_if/constexpr.cc: Likewise.
	* testsuite/25_algorithms/replace_if/constexpr.cc: Likewise.
	* testsuite/25_algorithms/reverse/constexpr.cc: Likewise.
	* testsuite/25_algorithms/reverse_copy/constexpr.cc: Likewise.
	* testsuite/25_algorithms/rotate_copy/constexpr.cc: Likewise.
	* testsuite/25_algorithms/search/constexpr.cc: Likewise.
	* testsuite/25_algorithms/set_difference/constexpr.cc: Likewise.
	* testsuite/25_algorithms/set_intersection/constexpr.cc:
	Likewise.
	* testsuite/25_algorithms/set_symmetric_difference/constexpr.cc:
	Likewise.
	* testsuite/25_algorithms/set_union/constexpr.cc: Likewise.
	* testsuite/25_algorithms/unique_copy/constexpr.cc: Likewise.
	* testsuite/25_algorithms/upper_bound/constexpr.cc: Likewise.
---
 .../testsuite/25_algorithms/all_of/constexpr.cc  | 13 ++++++-------
 .../testsuite/25_algorithms/any_of/constexpr.cc  |  5 ++++-
 .../25_algorithms/binary_search/constexpr.cc     |  5 ++++-
 .../25_algorithms/copy_backward/constexpr.cc     |  2 +-
 .../testsuite/25_algorithms/count/constexpr.cc   |  4 +++-
 .../testsuite/25_algorithms/equal/constexpr.cc   |  7 ++++++-
 .../25_algorithms/equal_range/constexpr.cc       |  3 ++-
 .../testsuite/25_algorithms/fill/constexpr.cc    |  2 +-
 .../25_algorithms/find_end/constexpr.cc          |  4 ++--
 .../testsuite/25_algorithms/find_if/constexpr.cc |  4 ++--
 .../25_algorithms/is_partitioned/constexpr.cc    |  2 +-
 .../25_algorithms/is_permutation/constexpr.cc    |  4 +++-
 .../25_algorithms/is_sorted_until/constexpr.cc   |  5 ++++-
 .../lexicographical_compare/constexpr.cc         |  2 +-
 .../25_algorithms/lower_bound/constexpr.cc       |  2 +-
 .../testsuite/25_algorithms/merge/constexpr.cc   |  4 +++-
 .../25_algorithms/mismatch/constexpr.cc          |  3 ++-
 .../testsuite/25_algorithms/none_of/constexpr.cc |  2 +-
 .../25_algorithms/partition_copy/constexpr.cc    |  3 ++-
 .../25_algorithms/remove_copy/constexpr.cc       |  4 ++--
 .../25_algorithms/remove_copy_if/constexpr.cc    |  2 +-
 .../25_algorithms/remove_if/constexpr.cc         |  2 +-
 .../25_algorithms/replace_if/constexpr.cc        |  4 +++-
 .../testsuite/25_algorithms/reverse/constexpr.cc |  2 --
 .../25_algorithms/reverse_copy/constexpr.cc      |  2 +-
 .../25_algorithms/rotate_copy/constexpr.cc       |  2 +-
 .../testsuite/25_algorithms/search/constexpr.cc  |  4 ++--
 .../25_algorithms/set_difference/constexpr.cc    |  9 ++++++---
 .../25_algorithms/set_intersection/constexpr.cc  |  2 +-
 .../set_symmetric_difference/constexpr.cc        | 16 +++++++++-------
 .../25_algorithms/set_union/constexpr.cc         |  5 +++--
 .../25_algorithms/unique_copy/constexpr.cc       |  5 +++--
 .../25_algorithms/upper_bound/constexpr.cc       |  2 +-
 33 files changed, 83 insertions(+), 54 deletions(-)

diff --git a/libstdc++-v3/testsuite/25_algorithms/all_of/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/all_of/constexpr.cc
index 11f1a337c20..757eebc89b6 100644
--- a/libstdc++-v3/testsuite/25_algorithms/all_of/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/all_of/constexpr.cc
@@ -23,13 +23,12 @@
 
 constexpr std::array<int, 6> cae{{0, 2, 4, 6, 8, 10}};
 
-constexpr auto out2 = std::all_of(cae.begin(), cae.end(),
+constexpr auto out1 = std::all_of(cae.begin(), cae.end(),
 			          [](int i){ return i % 2 == 0; });
 
-constexpr bool
-test()
-{
-  return true;
-}
+static_assert(out1);
+
+constexpr auto out2 = std::all_of(cae.begin(), cae.end(),
+			          [](int i){ return i != 8; });
 
-static_assert(test());
+static_assert(!out2);
diff --git a/libstdc++-v3/testsuite/25_algorithms/any_of/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/any_of/constexpr.cc
index 370f7f3614a..dadd4506179 100644
--- a/libstdc++-v3/testsuite/25_algorithms/any_of/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/any_of/constexpr.cc
@@ -29,7 +29,10 @@ test()
   const auto out3 = std::any_of(ca0.begin(), ca0.end(),
 			        [](int i){ return i % 2 == 0; });
 
-  return true;
+  const auto out4 = std::any_of(ca0.begin(), ca0.end(),
+			        [](int i){ return i == -1; });
+
+  return out3 && !out4;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/binary_search/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/binary_search/constexpr.cc
index 0e355cc9ba7..f82a6893b48 100644
--- a/libstdc++-v3/testsuite/25_algorithms/binary_search/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/binary_search/constexpr.cc
@@ -31,7 +31,10 @@ test()
   const auto out5 = std::binary_search(ca0.begin(), ca0.end(), 5,
 				       std::less<int>());
 
-  return true;
+  const auto out6 = std::binary_search(ca0.begin(), ca0.end(), 4.5,
+				       std::less<>());
+
+  return out4 && out5 && !out6;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/copy_backward/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/copy_backward/constexpr.cc
index 704dcf513c0..e97e30e0777 100644
--- a/libstdc++-v3/testsuite/25_algorithms/copy_backward/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/copy_backward/constexpr.cc
@@ -30,7 +30,7 @@ test()
   const auto out7 = std::copy_backward(ca0.begin(), ca0.begin() + 8,
 				       ma0.begin() + 10);
 
-  return true;
+  return out7 == ma0.begin() + 2 && ma0[3] == 1;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/count/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/count/constexpr.cc
index 6b6a2801207..3b900a9ca07 100644
--- a/libstdc++-v3/testsuite/25_algorithms/count/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/count/constexpr.cc
@@ -28,7 +28,9 @@ test()
 
   const auto out8 = std::count(ca0.begin(), ca0.end(), 6);
 
-  return true;
+  const auto out9 = std::count(ca0.begin(), ca0.end(), 16);
+
+  return out8 == 1 && out9 == 0;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/equal/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/equal/constexpr.cc
index a3ebee5db90..ca1b7bc5bd9 100644
--- a/libstdc++-v3/testsuite/25_algorithms/equal/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/equal/constexpr.cc
@@ -33,7 +33,12 @@ test()
   const auto outb = std::equal(ca0.begin(), ca0.end(), cas.begin(),
 			       [](int i, int j){ return i + 3 == j; });
 
-  return true;
+  auto ca2 = ca0;
+  ca2[5] = -1;
+
+  const auto outc = std::equal(ca0.begin(), ca0.end(), ca2.begin());
+
+  return outa && outb && !outc;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/equal_range/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/equal_range/constexpr.cc
index 0bd1b0de48c..2b46f5f6759 100644
--- a/libstdc++-v3/testsuite/25_algorithms/equal_range/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/equal_range/constexpr.cc
@@ -28,7 +28,8 @@ test()
 
   const auto outc = std::equal_range(car.begin(), car.end(), 6);
 
-  return true;
+  return outc.first == (car.begin() + 6)
+    && outc.second == (car.begin() + 8);
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/fill/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/fill/constexpr.cc
index ec69a7f432a..154e48b3849 100644
--- a/libstdc++-v3/testsuite/25_algorithms/fill/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/fill/constexpr.cc
@@ -27,7 +27,7 @@ test()
   std::array<int, 12> ma0{{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}};
   std::fill(ma0.begin(), ma0.end(), 66);
 
-  return true;
+  return ma0[4] == 66 && ma0[7] == 66;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/find_end/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/find_end/constexpr.cc
index c5ba3974cfd..9339ab06ae6 100644
--- a/libstdc++-v3/testsuite/25_algorithms/find_end/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/find_end/constexpr.cc
@@ -24,7 +24,7 @@
 constexpr bool
 test()
 {
-  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5,  6, 7, 8,  9, 10, 11}};
+  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
   constexpr std::array<int, 3> cam{{4, 5, 6}};
   constexpr std::array<int, 3> camm{{-4, -5, -6}};
 
@@ -35,7 +35,7 @@ test()
 				  camm.begin(), camm.end(),
 				  [](int i, int j){ return i + 1 == -j; });
 
-  return true;
+  return outf == (ca0.begin() + 4) && outg == (ca0.begin() + 3);
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/find_if/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/find_if/constexpr.cc
index b4064e6f690..6c88c49c75e 100644
--- a/libstdc++-v3/testsuite/25_algorithms/find_if/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/find_if/constexpr.cc
@@ -24,12 +24,12 @@
 constexpr bool
 test()
 {
-  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5,  6, 7, 8,  9, 10, 11}};
+  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
 
   const auto outj = std::find_if(ca0.begin(), ca0.end(),
 				 [](int i){ return i == 6; });
 
-  return true;
+  return outj == (ca0.begin() + 6);
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/is_partitioned/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/is_partitioned/constexpr.cc
index deab94d019d..163f9bd2d1d 100644
--- a/libstdc++-v3/testsuite/25_algorithms/is_partitioned/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/is_partitioned/constexpr.cc
@@ -29,7 +29,7 @@ test()
   const auto outs = std::is_partitioned(caeo.begin(), caeo.end(),
 					[](int i){ return i % 2 == 0; });
 
-  return true;
+  return outs;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/is_permutation/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/is_permutation/constexpr.cc
index 1da8bbee30e..1567c2658ff 100644
--- a/libstdc++-v3/testsuite/25_algorithms/is_permutation/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/is_permutation/constexpr.cc
@@ -29,7 +29,9 @@ test()
 
   const auto outt = std::is_permutation(ca0.begin(), ca0.end(), cap.begin());
 
-  return true;
+  const auto outf = std::is_permutation(ca0.begin() + 1, ca0.end(), cap.begin());
+
+  return outt && !outf;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/is_sorted_until/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/is_sorted_until/constexpr.cc
index d000e555ae7..3c540559c31 100644
--- a/libstdc++-v3/testsuite/25_algorithms/is_sorted_until/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/is_sorted_until/constexpr.cc
@@ -31,7 +31,10 @@ test()
   const auto outy = std::is_sorted_until(aus.begin(), aus.end(),
 					 std::less<int>());
 
-  return true;
+  const auto outz = std::is_sorted_until(outx - 1, aus.end(),
+					 std::greater<int>());
+
+  return outx == aus.begin() + 7 && outy == outx && outz == (outx + 1);
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/lexicographical_compare/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/lexicographical_compare/constexpr.cc
index 7046f4489d6..1d7502c27c6 100644
--- a/libstdc++-v3/testsuite/25_algorithms/lexicographical_compare/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/lexicographical_compare/constexpr.cc
@@ -34,7 +34,7 @@ test()
 						   ca1.begin(), ca1.end(),
 						   std::less<int>());
 
-  return true;
+  return outz && outaa;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/lower_bound/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/lower_bound/constexpr.cc
index 1b570a2ce54..ec5da9b3227 100644
--- a/libstdc++-v3/testsuite/25_algorithms/lower_bound/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/lower_bound/constexpr.cc
@@ -31,7 +31,7 @@ test()
   const auto outcc = std::lower_bound(ca0.begin(), ca0.end(), 6,
 				      std::less<int>());
 
-  return true;
+  return outbb == (ca0.begin() + 6) && outcc == outbb;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/merge/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/merge/constexpr.cc
index d46b5787b7c..02493581635 100644
--- a/libstdc++-v3/testsuite/25_algorithms/merge/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/merge/constexpr.cc
@@ -31,12 +31,14 @@ test()
 
   const auto outdd = std::merge(ca0.begin(), ca0.end(),
 				cas.begin(), cas.end(), out0.begin());
+  if (outdd != out0.end())
+    return false;
 
   const auto outee = std::merge(ca0.begin(), ca0.end(),
 				camm.begin(), camm.end(), out0.begin(),
 				[](int i, int j){ return i < j; });
 
-  return true;
+  return outee == (out0.begin() + ca0.size() + camm.size());
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/mismatch/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/mismatch/constexpr.cc
index 868bb41e1cb..f2cc21d03d8 100644
--- a/libstdc++-v3/testsuite/25_algorithms/mismatch/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/mismatch/constexpr.cc
@@ -32,7 +32,8 @@ test()
   const auto outgg = std::mismatch(ca0.begin(), ca0.end(), cax.begin(),
 				   std::equal_to<int>());
 
-  return true;
+  return outff.first == (ca0.begin() + 6) && outff.second == (cax.begin() + 6)
+    && outgg == outff;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/none_of/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/none_of/constexpr.cc
index cea4fc61f90..245ebe47dcb 100644
--- a/libstdc++-v3/testsuite/25_algorithms/none_of/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/none_of/constexpr.cc
@@ -29,7 +29,7 @@ test()
   const auto outhh = std::none_of(ca0.begin(), ca0.end(),
 				  [](int i){ return i > 12; });
 
-  return true;
+  return outhh;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/partition_copy/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/partition_copy/constexpr.cc
index e7cb3087b2c..21685636ecd 100644
--- a/libstdc++-v3/testsuite/25_algorithms/partition_copy/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/partition_copy/constexpr.cc
@@ -32,7 +32,8 @@ test()
 					 out0.begin(), out1.begin(),
 					 [](int i){ return i % 2 == 0; });
 
-  return true;
+  return outii.first == (out0.begin() + 6) && out0[1] == 2
+    && outii.second == (out1.begin() + 6) && out1[1] == 3;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/remove_copy/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/remove_copy/constexpr.cc
index 0474feccb09..e82a506abb0 100644
--- a/libstdc++-v3/testsuite/25_algorithms/remove_copy/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/remove_copy/constexpr.cc
@@ -24,12 +24,12 @@
 constexpr bool
 test()
 {
-  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5,  6, 7, 8,  9, 10, 11}};
+  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
   std::array<int, 24> out0{{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}};
 
   const auto outmm = std::remove_copy(ca0.begin(), ca0.end(), out0.begin(), 6);
 
-  return true;
+  return outmm == out0.begin() + ca0.size() - 1;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/remove_copy_if/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/remove_copy_if/constexpr.cc
index 813be78c133..f8133fc24f5 100644
--- a/libstdc++-v3/testsuite/25_algorithms/remove_copy_if/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/remove_copy_if/constexpr.cc
@@ -30,7 +30,7 @@ test()
   const auto outnn = std::remove_copy_if(ca0.begin(), ca0.end(), out0.begin(),
 					 [](int i){ return i == 7; });
 
-  return true;
+  return outnn == out0.begin() + ca0.size() - 1;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/remove_if/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/remove_if/constexpr.cc
index c2d98f2a68e..d590d4d5ea1 100644
--- a/libstdc++-v3/testsuite/25_algorithms/remove_if/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/remove_if/constexpr.cc
@@ -29,7 +29,7 @@ test()
   const auto outll = std::remove_if(ac2.begin(), ac2.end(),
 				    [](int i){ return i == 7; });
 
-  return true;
+  return outll == (ac2.end() - 1) && ac2[7] == 8;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/replace_if/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/replace_if/constexpr.cc
index 6bcc0bd72ae..4b293f48aa9 100644
--- a/libstdc++-v3/testsuite/25_algorithms/replace_if/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/replace_if/constexpr.cc
@@ -28,7 +28,9 @@ test()
 
   std::replace_if(ar0.begin(), ar0.end(), [](int i){ return i % 2 == 1; }, 42);
 
-  return true;
+  std::array<int, 12> ar1{{0, 42, 2, 42, 4, 42, 6, 6, 8, 42, 42, 42}};
+
+  return ar0 == ar1;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/reverse/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/reverse/constexpr.cc
index ba1f47b6127..15140014a09 100644
--- a/libstdc++-v3/testsuite/25_algorithms/reverse/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/reverse/constexpr.cc
@@ -23,8 +23,6 @@
 constexpr bool
 test()
 {
-  auto ok = true;
-
   std::array<int, 12> ar0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
 
   std::reverse(ar0.begin() + 2, ar0.begin() + 9);
diff --git a/libstdc++-v3/testsuite/25_algorithms/reverse_copy/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/reverse_copy/constexpr.cc
index 86214e1d30e..9a85e591edd 100644
--- a/libstdc++-v3/testsuite/25_algorithms/reverse_copy/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/reverse_copy/constexpr.cc
@@ -29,7 +29,7 @@ test()
 
   const auto outqq = std::reverse_copy(ca0.rbegin(), ca0.rend(), out0.begin());
 
-  return true;
+  return outqq == (out0.begin() + ca0.size()) && out0[3] == 3;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/rotate_copy/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/rotate_copy/constexpr.cc
index f8377b8a24c..8d9d966ba03 100644
--- a/libstdc++-v3/testsuite/25_algorithms/rotate_copy/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/rotate_copy/constexpr.cc
@@ -30,7 +30,7 @@ test()
   const auto outrr = std::rotate_copy(ca0.begin(), ca0.begin() + 6,
 				      ca0.end(), out0.begin());
 
-  return true;
+  return outrr == (out0.begin() + ca0.size()) && out0[3] == 9 && out0[8] == 2;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/search/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/search/constexpr.cc
index e34194cfc5d..557234ec819 100644
--- a/libstdc++-v3/testsuite/25_algorithms/search/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/search/constexpr.cc
@@ -24,7 +24,7 @@
 constexpr bool
 test()
 {
-  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5,  6, 7, 8,  9, 10, 11}};
+  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
   constexpr std::array<int, 3> cam{{4, 5, 6}};
 
   const auto outtt = std::search(ca0.begin(), ca0.end(),
@@ -35,7 +35,7 @@ test()
     = std::search(ca0.begin(), ca0.end(),
 		  std::default_searcher(cam.begin(), cam.end()));
 
-  return true;
+  return outtt == (ca0.begin() + 4) && outtt2 == outtt;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/set_difference/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/set_difference/constexpr.cc
index ef0f7184604..f66c957df80 100644
--- a/libstdc++-v3/testsuite/25_algorithms/set_difference/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/set_difference/constexpr.cc
@@ -29,13 +29,16 @@ test()
   std::array<int, 24> out0{{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}};
 
   const auto outvv = std::set_difference(ca0.begin(), ca0.end(),
-					 cas.begin(), cas.end(), out0.begin());
+					 cas.begin(), cas.end(),
+					 out0.begin());
 
   const auto outww = std::set_difference(ca0.begin(), ca0.end(),
 				         cas.begin(), cas.end(),
-				         out0.begin(), std::less<int>());
+				         outvv,
+					 std::less<int>());
 
-  return true;
+
+  return outvv == (out0.begin() + 3) && outww == (outvv + 3);
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/set_intersection/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/set_intersection/constexpr.cc
index b415020943a..720e8a5a6c0 100644
--- a/libstdc++-v3/testsuite/25_algorithms/set_intersection/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/set_intersection/constexpr.cc
@@ -36,7 +36,7 @@ test()
 					   cas.begin(), cas.end(),
 					   out0.begin(), std::less<int>());
 
-  return true;
+  return outxx == (out0.begin() + 9) && outyy == outxx;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/set_symmetric_difference/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/set_symmetric_difference/constexpr.cc
index ef0f7184604..0505aaf2519 100644
--- a/libstdc++-v3/testsuite/25_algorithms/set_symmetric_difference/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/set_symmetric_difference/constexpr.cc
@@ -25,17 +25,19 @@ constexpr bool
 test()
 {
   constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
-  constexpr std::array<int, 12> cas{{3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14}};
+  constexpr std::array<int, 12> cas{{4, 4, 5, 6, 7, 8, 9, 10, 11, 11, 12, 13}};
   std::array<int, 24> out0{{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}};
 
-  const auto outvv = std::set_difference(ca0.begin(), ca0.end(),
-					 cas.begin(), cas.end(), out0.begin());
+  const auto outvv = std::set_symmetric_difference(ca0.begin(), ca0.end(),
+						   cas.begin(), cas.end(),
+						   out0.begin());
 
-  const auto outww = std::set_difference(ca0.begin(), ca0.end(),
-				         cas.begin(), cas.end(),
-				         out0.begin(), std::less<int>());
+  const auto outww = std::set_symmetric_difference(ca0.begin(), ca0.end(),
+						   cas.begin(), cas.end(),
+						   out0.begin(),
+						   std::less<int>());
 
-  return true;
+  return outvv == (out0.begin() + 8) && outww == outvv;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/set_union/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/set_union/constexpr.cc
index fccfe2099d7..87f3f27f9e1 100644
--- a/libstdc++-v3/testsuite/25_algorithms/set_union/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/set_union/constexpr.cc
@@ -29,13 +29,14 @@ test()
   std::array<int, 24> out0{{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}};
 
   const auto out11 = std::set_union(ca0.begin(), ca0.end(),
-				    cas.begin(), cas.end(), out0.begin());
+				    cas.begin(), cas.end(),
+				    out0.begin());
 
   const auto out22 = std::set_union(ca0.begin(), ca0.end(),
 				    cas.begin(), cas.end(),
 				    out0.begin(), std::less<int>());
 
-  return true;
+  return out11 == (out0.begin() + 15) && out22 == out11;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/unique_copy/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/unique_copy/constexpr.cc
index 167dc55add6..ee372b8488d 100644
--- a/libstdc++-v3/testsuite/25_algorithms/unique_copy/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/unique_copy/constexpr.cc
@@ -29,10 +29,11 @@ test()
 
   const auto out55 = std::unique_copy(ar3.begin(), ar3.end(), out0.begin());
 
-  const auto out66 = std::unique_copy(ar3.begin(), ar3.end(), out0.begin(),
+  const auto out66 = std::unique_copy(ar3.begin(), ar3.end(), out55,
 				      std::equal_to<int>());
 
-  return true;
+  return out55 == (out0.begin() + 10) && out0[7] == 8
+    && out66 == (out55 + 10) ; // && out0[19] == 11;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/upper_bound/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/upper_bound/constexpr.cc
index 8dedb6bd615..3479116c210 100644
--- a/libstdc++-v3/testsuite/25_algorithms/upper_bound/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/upper_bound/constexpr.cc
@@ -31,7 +31,7 @@ test()
   const auto out88 = std::upper_bound(ca0.begin(), ca0.end(), 6,
 				      std::less<int>());
 
-  return true;
+  return out77 == (ca0.begin() + 7) && out88 == out77;
 }
 
 static_assert(test());
-- 
2.30.2