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.

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 11f1a33..757eebc 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 370f7f3..dadd450 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 0e355cc..f82a689 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 704dcf5..e97e30e 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 6b6a280..3b900a9 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 a3ebee5..ca1b7bc 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 0bd1b0d..2b46f5f 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 ec69a7f..154e48b 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 c5ba397..9339ab0 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 b4064e6..6c88c49 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 deab94d..163f9bd 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 1da8bbe..1567c26 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 d000e55..3c54055 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 7046f44..1d7502c 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 1b570a2..ec5da9b3 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 d46b578..0249358 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 868bb41..f2cc21d 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 cea4fc6..245ebe4 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 e7cb308..2168563 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 0474fec..e82a506 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 813be78c..f8133fc 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 c2d98f2..d590d4d 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 6bcc0bd..4b293f4 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 ba1f47b..1514001 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 86214e1..9a85e59 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 f8377b8..8d9d966 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 e34194c..557234e 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 ef0f7184..f66c957 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 b415020..720e8a5 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 ef0f7184..0505aaf 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 fccfe20..87f3f27 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 167dc55..ee372b8 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 8dedb6b..3479116 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());