Index: test/std/algorithms/alg.modifying.operations/alg.random.sample/sample.pass.cpp
===================================================================
--- test/std/algorithms/alg.modifying.operations/alg.random.sample/sample.pass.cpp
+++ test/std/algorithms/alg.modifying.operations/alg.random.sample/sample.pass.cpp
@@ -21,6 +21,7 @@
 #include <random>
 #include <type_traits>
 #include <cassert>
+#include <cstddef>
 
 #include "test_iterators.h"
 #include "test_macros.h"
@@ -70,14 +71,14 @@
   end = std::sample(PopulationIterator(ia),
                                   PopulationIterator(ia + is),
                                   SampleIterator(oa), os, g);
-  assert(end.base() - oa == std::min(os, is));
+  assert(static_cast<std::size_t>(end.base() - oa) == std::min(os, is));
   // sample() is deterministic but non-reproducible;
   // its results can vary between implementations.
   LIBCPP_ASSERT(std::equal(oa, oa + os, oa1));
   end = std::sample(PopulationIterator(ia),
                                   PopulationIterator(ia + is),
                                   SampleIterator(oa), os, std::move(g));
-  assert(end.base() - oa == std::min(os, is));
+  assert(static_cast<std::size_t>(end.base() - oa) == std::min(os, is));
   LIBCPP_ASSERT(std::equal(oa, oa + os, oa2));
 }
 
@@ -127,7 +128,7 @@
   end = std::sample(PopulationIterator(ia),
                                   PopulationIterator(ia + is),
                                   SampleIterator(oa), os, g);
-  assert(end.base() - oa == std::min(os, is));
+  assert(static_cast<std::size_t>(end.base() - oa) == std::min(os, is));
   typedef typename std::iterator_traits<PopulationIterator>::iterator_category PopulationCategory;
   if (std::is_base_of<std::forward_iterator_tag, PopulationCategory>::value) {
     assert(std::equal(oa, end.base(), oa1));
Index: test/std/containers/container.adaptors/priority.queue/priqueue.cons/ctor_iter_iter.pass.cpp
===================================================================
--- test/std/containers/container.adaptors/priority.queue/priqueue.cons/ctor_iter_iter.pass.cpp
+++ test/std/containers/container.adaptors/priority.queue/priqueue.cons/ctor_iter_iter.pass.cpp
@@ -14,12 +14,13 @@
 
 #include <queue>
 #include <cassert>
+#include <cstddef>
 
 int main()
 {
     int a[] = {3, 5, 2, 0, 6, 8, 1};
     int* an = a + sizeof(a)/sizeof(a[0]);
     std::priority_queue<int> q(a, an);
-    assert(q.size() == an - a);
+    assert(q.size() == static_cast<std::size_t>(an - a));
     assert(q.top() == 8);
 }
Index: test/std/containers/container.adaptors/priority.queue/priqueue.cons/ctor_iter_iter_comp.pass.cpp
===================================================================
--- test/std/containers/container.adaptors/priority.queue/priqueue.cons/ctor_iter_iter_comp.pass.cpp
+++ test/std/containers/container.adaptors/priority.queue/priqueue.cons/ctor_iter_iter_comp.pass.cpp
@@ -15,6 +15,7 @@
 #include <queue>
 #include <cassert>
 #include <functional>
+#include <cstddef>
 
 int main()
 {
@@ -22,6 +23,6 @@
     int* an = a + sizeof(a)/sizeof(a[0]);
     std::priority_queue<int, std::vector<int>, std::greater<int> >
         q(a, an, std::greater<int>());
-    assert(q.size() == an - a);
+    assert(q.size() == static_cast<std::size_t>(an - a));
     assert(q.top() == 0);
 }
Index: test/std/containers/sequences/deque/deque.capacity/resize_size.pass.cpp
===================================================================
--- test/std/containers/sequences/deque/deque.capacity/resize_size.pass.cpp
+++ test/std/containers/sequences/deque/deque.capacity/resize_size.pass.cpp
@@ -49,7 +49,7 @@
     typedef typename C::const_iterator CI;
     typename C::size_type c1_osize = c1.size();
     c1.resize(size);
-    assert(c1.size() == size);
+    assert(c1.size() == static_cast<std::size_t>(size));
     assert(static_cast<std::size_t>(distance(c1.begin(), c1.end())) == c1.size());
     CI i = c1.begin();
     for (int j = 0; static_cast<std::size_t>(j) < std::min(c1_osize, c1.size()); ++j, ++i)
Index: test/std/containers/sequences/deque/deque.capacity/resize_size_value.pass.cpp
===================================================================
--- test/std/containers/sequences/deque/deque.capacity/resize_size_value.pass.cpp
+++ test/std/containers/sequences/deque/deque.capacity/resize_size_value.pass.cpp
@@ -49,7 +49,7 @@
     typedef typename C::const_iterator CI;
     typename C::size_type c1_osize = c1.size();
     c1.resize(size, x);
-    assert(c1.size() == size);
+    assert(c1.size() == static_cast<std::size_t>(size));
     assert(static_cast<std::size_t>(distance(c1.begin(), c1.end())) == c1.size());
     CI i = c1.begin();
     for (int j = 0; static_cast<std::size_t>(j) < std::min(c1_osize, c1.size()); ++j, ++i)
Index: test/std/containers/sequences/deque/deque.cons/assign_size_value.pass.cpp
===================================================================
--- test/std/containers/sequences/deque/deque.cons/assign_size_value.pass.cpp
+++ test/std/containers/sequences/deque/deque.cons/assign_size_value.pass.cpp
@@ -47,7 +47,7 @@
 {
     typedef typename C::const_iterator CI;
     c1.assign(size, v);
-    assert(c1.size() == size);
+    assert(c1.size() == static_cast<std::size_t>(size));
     assert(static_cast<std::size_t>(distance(c1.begin(), c1.end())) == c1.size());
     for (CI i = c1.begin(); i != c1.end(); ++i)
         assert(*i == v);
Index: test/std/containers/sequences/forwardlist/forwardlist.cons/size.pass.cpp
===================================================================
--- test/std/containers/sequences/forwardlist/forwardlist.cons/size.pass.cpp
+++ test/std/containers/sequences/forwardlist/forwardlist.cons/size.pass.cpp
@@ -14,6 +14,7 @@
 
 #include <forward_list>
 #include <cassert>
+#include <cstddef>
 
 #include "test_macros.h"
 #include "DefaultOnly.h"
@@ -26,7 +27,7 @@
     typedef std::forward_list<T, Allocator> C;
     C d(n, alloc);
     assert(d.get_allocator() == alloc);
-    assert(std::distance(d.begin(), d.end()) == n);
+    assert(static_cast<std::size_t>(std::distance(d.begin(), d.end())) == n);
 #endif
 }
 
Index: test/std/containers/sequences/forwardlist/forwardlist.ops/remove_if.pass.cpp
===================================================================
--- test/std/containers/sequences/forwardlist/forwardlist.ops/remove_if.pass.cpp
+++ test/std/containers/sequences/forwardlist/forwardlist.ops/remove_if.pass.cpp
@@ -14,6 +14,7 @@
 #include <forward_list>
 #include <iterator>
 #include <cassert>
+#include <cstddef>
 
 #include "min_allocator.h"
 #include "counting_predicates.hpp"
@@ -37,7 +38,7 @@
         Predicate cp(g);
         c1.remove_if(std::ref(cp));
         assert(c1 == c2);
-        assert(cp.count() == std::distance(std::begin(t1), std::end(t1)));
+        assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
     }
     {
         typedef int T;
@@ -49,7 +50,7 @@
         Predicate cp(g);
         c1.remove_if(std::ref(cp));
         assert(c1 == c2);
-        assert(cp.count() == std::distance(std::begin(t1), std::end(t1)));
+        assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
     }
     {
         typedef int T;
@@ -62,7 +63,7 @@
         Predicate cp(g);
         c1.remove_if(std::ref(cp));
         assert(c1 == c2);
-        assert(cp.count() == std::distance(std::begin(t1), std::end(t1)));
+        assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
     }
     {
         typedef int T;
@@ -86,7 +87,7 @@
         Predicate cp(g);
         c1.remove_if(std::ref(cp));
         assert(c1 == c2);
-        assert(cp.count() == std::distance(std::begin(t1), std::end(t1)));
+        assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
     }
 #if TEST_STD_VER >= 11
     {
@@ -100,7 +101,7 @@
         Predicate cp(g);
         c1.remove_if(std::ref(cp));
         assert(c1 == c2);
-        assert(cp.count() == std::distance(std::begin(t1), std::end(t1)));
+        assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
     }
     {
         typedef int T;
@@ -112,7 +113,7 @@
         Predicate cp(g);
         c1.remove_if(std::ref(cp));
         assert(c1 == c2);
-        assert(cp.count() == std::distance(std::begin(t1), std::end(t1)));
+        assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
     }
     {
         typedef int T;
@@ -125,7 +126,7 @@
         Predicate cp(g);
         c1.remove_if(std::ref(cp));
         assert(c1 == c2);
-        assert(cp.count() == std::distance(std::begin(t1), std::end(t1)));
+        assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
     }
     {
         typedef int T;
@@ -149,7 +150,7 @@
         Predicate cp(g);
         c1.remove_if(std::ref(cp));
         assert(c1 == c2);
-        assert(cp.count() == std::distance(std::begin(t1), std::end(t1)));
+        assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
     }
 #endif
 }
Index: test/std/containers/sequences/list/list.cons/size_type.pass.cpp
===================================================================
--- test/std/containers/sequences/list/list.cons/size_type.pass.cpp
+++ test/std/containers/sequences/list/list.cons/size_type.pass.cpp
@@ -13,6 +13,7 @@
 
 #include <list>
 #include <cassert>
+#include <cstddef>
 #include "test_macros.h"
 #include "DefaultOnly.h"
 #include "test_allocator.h"
@@ -28,7 +29,7 @@
     {
     C d(n, alloc);
     assert(d.size() == n);
-    assert(std::distance(d.begin(), d.end()) == n);
+    assert(static_cast<std::size_t>(std::distance(d.begin(), d.end())) == n);
     assert(d.get_allocator() == alloc);
     }
 #endif
Index: test/std/containers/sequences/vector.bool/find.pass.cpp
===================================================================
--- test/std/containers/sequences/vector.bool/find.pass.cpp
+++ test/std/containers/sequences/vector.bool/find.pass.cpp
@@ -17,6 +17,7 @@
 #include <vector>
 #include <algorithm>
 #include <cassert>
+#include <cstddef>
 
 int main()
 {
@@ -25,7 +26,7 @@
         {
             std::vector<bool> b(i,true);
             std::vector<bool>::iterator j = std::find(b.begin()+1, b.end(), false);
-            assert(j-b.begin() == i);
+            assert(static_cast<std::size_t>(j-b.begin()) == i);
             assert(b.end() == j);
         }
     }
@@ -34,7 +35,7 @@
         {
             std::vector<bool> b(i,false);
             std::vector<bool>::iterator j = std::find(b.begin()+1, b.end(), true);
-            assert(j-b.begin() == i);
+            assert(static_cast<std::size_t>(j-b.begin()) == i);
             assert(b.end() == j);
         }
     }
Index: test/std/language.support/support.initlist/support.initlist.access/access.pass.cpp
===================================================================
--- test/std/language.support/support.initlist/support.initlist.access/access.pass.cpp
+++ test/std/language.support/support.initlist/support.initlist.access/access.pass.cpp
@@ -15,6 +15,7 @@
 
 #include <initializer_list>
 #include <cassert>
+#include <cstddef>
 
 #include "test_macros.h"
 
@@ -27,7 +28,7 @@
         const int* b = il.begin();
         const int* e = il.end();
         assert(il.size() == 3);
-        assert(e - b == il.size());
+        assert(static_cast<std::size_t>(e - b) == il.size());
         assert(*b++ == 3);
         assert(*b++ == 2);
         assert(*b++ == 1);
@@ -42,7 +43,7 @@
         const int* b = il.begin();
         const int* e = il.end();
         assert(il.size() == 3);
-        assert(e - b == il.size());
+        assert(static_cast<std::size_t>(e - b) == il.size());
         assert(*b++ == 3);
         assert(*b++ == 2);
         assert(*b++ == 1);
Index: test/std/language.support/support.initlist/support.initlist.range/begin_end.pass.cpp
===================================================================
--- test/std/language.support/support.initlist/support.initlist.range/begin_end.pass.cpp
+++ test/std/language.support/support.initlist/support.initlist.range/begin_end.pass.cpp
@@ -13,6 +13,7 @@
 
 #include <initializer_list>
 #include <cassert>
+#include <cstddef>
 
 #include "test_macros.h"
 
@@ -25,7 +26,7 @@
         const int* b = begin(il);
         const int* e = end(il);
         assert(il.size() == 3);
-        assert(e - b == il.size());
+        assert(static_cast<std::size_t>(e - b) == il.size());
         assert(*b++ == 3);
         assert(*b++ == 2);
         assert(*b++ == 1);
@@ -40,7 +41,7 @@
         const int* b = begin(il);
         const int* e = end(il);
         assert(il.size() == 3);
-        assert(e - b == il.size());
+        assert(static_cast<std::size_t>(e - b) == il.size());
         assert(*b++ == 3);
         assert(*b++ == 2);
         assert(*b++ == 1);
Index: test/std/localization/locale.categories/category.ctype/locale.codecvt/locale.codecvt.members/wchar_t_in.pass.cpp
===================================================================
--- test/std/localization/locale.categories/category.ctype/locale.codecvt/locale.codecvt.members/wchar_t_in.pass.cpp
+++ test/std/localization/locale.categories/category.ctype/locale.codecvt/locale.codecvt.members/wchar_t_in.pass.cpp
@@ -19,6 +19,7 @@
 #include <string>
 #include <vector>
 #include <cassert>
+#include <cstddef>
 
 typedef std::codecvt<wchar_t, char, std::mbstate_t> F;
 
@@ -35,8 +36,8 @@
     F::result r = f.in(mbs, from.data(), from.data() + from.size(), from_next,
                             &to[0], &to[0] + to.size(), to_next);
     assert(r == F::ok);
-    assert(from_next - from.data() == from.size());
-    assert(to_next - to.data() == expected.size());
-    assert(to_next - to.data() == expected.size());
+    assert(static_cast<std::size_t>(from_next - from.data()) == from.size());
+    assert(static_cast<std::size_t>(to_next - to.data()) == expected.size());
+    assert(static_cast<std::size_t>(to_next - to.data()) == expected.size());
     assert(to == expected);
 }
Index: test/std/localization/locale.categories/category.ctype/locale.codecvt/locale.codecvt.members/wchar_t_out.pass.cpp
===================================================================
--- test/std/localization/locale.categories/category.ctype/locale.codecvt/locale.codecvt.members/wchar_t_out.pass.cpp
+++ test/std/localization/locale.categories/category.ctype/locale.codecvt/locale.codecvt.members/wchar_t_out.pass.cpp
@@ -19,6 +19,7 @@
 #include <string>
 #include <vector>
 #include <cassert>
+#include <cstddef>
 
 typedef std::codecvt<wchar_t, char, std::mbstate_t> F;
 
@@ -35,8 +36,8 @@
         F::result r = f.out(mbs, from.data(), from.data() + from.size(), from_next,
                                  to.data(), to.data() + to.size(), to_next);
         assert(r == F::ok);
-        assert(from_next - from.data() == from.size());
-        assert(to_next - to.data() == from.size());
+        assert(static_cast<std::size_t>(from_next - from.data()) == from.size());
+        assert(static_cast<std::size_t>(to_next - to.data()) == from.size());
         assert(to.data() == std::string("some text"));
     }
     {
@@ -49,8 +50,8 @@
         F::result r = f.out(mbs, from.data(), from.data() + from.size(), from_next,
                                  to.data(), to.data() + to.size(), to_next);
         assert(r == F::ok);
-        assert(from_next - from.data() == from.size());
-        assert(to_next - to.data() == from.size());
+        assert(static_cast<std::size_t>(from_next - from.data()) == from.size());
+        assert(static_cast<std::size_t>(to_next - to.data()) == from.size());
         assert(memcmp(to.data(), "some\0text", from.size()) == 0);
     }
     {
@@ -62,8 +63,8 @@
         F::result r = f.out(mbs, from.data(), from.data() + from.size(), from_next,
                                  to.data(), to.data() + to.size()-1, to_next);
         assert(r == F::partial);
-        assert(from_next - from.data() == to.size()-1);
-        assert(to_next - to.data() == to.size()-1);
+        assert(static_cast<std::size_t>(from_next - from.data()) == to.size()-1);
+        assert(static_cast<std::size_t>(to_next - to.data()) == to.size()-1);
         assert(to.data() == std::string("some te"));
     }
 }
Index: test/std/numerics/numarray/valarray.range/end_const.pass.cpp
===================================================================
--- test/std/numerics/numarray/valarray.range/end_const.pass.cpp
+++ test/std/numerics/numarray/valarray.range/end_const.pass.cpp
@@ -17,6 +17,7 @@
 
 #include <valarray>
 #include <cassert>
+#include <cstddef>
 
 int main()
 {
@@ -26,6 +27,6 @@
         const unsigned N = sizeof(a)/sizeof(a[0]);
         const std::valarray<T> v(a, N);
         assert(v[v.size()-1] == 5);
-        assert(end(v) - begin(v) == v.size());
+        assert(static_cast<std::size_t>(end(v) - begin(v)) == v.size());
     }
 }
Index: test/std/numerics/numarray/valarray.range/end_non_const.pass.cpp
===================================================================
--- test/std/numerics/numarray/valarray.range/end_non_const.pass.cpp
+++ test/std/numerics/numarray/valarray.range/end_non_const.pass.cpp
@@ -17,6 +17,7 @@
 
 #include <valarray>
 #include <cassert>
+#include <cstddef>
 
 int main()
 {
@@ -27,6 +28,6 @@
         std::valarray<T> v(a, N);
         *(end(v) - 1) = 10;
         assert(v[v.size()-1] == 10);
-        assert(end(v) - begin(v) == v.size());
+        assert(static_cast<std::size_t>(end(v) - begin(v)) == v.size());
     }
 }
Index: test/std/re/re.results/re.results.acc/begin_end.pass.cpp
===================================================================
--- test/std/re/re.results/re.results.acc/begin_end.pass.cpp
+++ test/std/re/re.results/re.results.acc/begin_end.pass.cpp
@@ -16,6 +16,7 @@
 
 #include <regex>
 #include <cassert>
+#include <cstddef>
 #include "test_macros.h"
 
 void
@@ -28,7 +29,7 @@
     std::match_results<const char*>::const_iterator i = m.begin();
     std::match_results<const char*>::const_iterator e = m.end();
 
-    assert(e - i == m.size());
+    assert(static_cast<std::size_t>(e - i) == m.size());
     for (int j = 0; i != e; ++i, ++j)
         assert(*i == m[j]);
 }
Index: test/std/re/re.results/re.results.acc/cbegin_cend.pass.cpp
===================================================================
--- test/std/re/re.results/re.results.acc/cbegin_cend.pass.cpp
+++ test/std/re/re.results/re.results.acc/cbegin_cend.pass.cpp
@@ -16,6 +16,7 @@
 
 #include <regex>
 #include <cassert>
+#include <cstddef>
 #include "test_macros.h"
 
 void
@@ -28,7 +29,7 @@
     std::match_results<const char*>::const_iterator i = m.cbegin();
     std::match_results<const char*>::const_iterator e = m.cend();
 
-    assert(e - i == m.size());
+    assert(static_cast<std::size_t>(e - i) == m.size());
     for (int j = 0; i != e; ++i, ++j)
         assert(*i == m[j]);
 }
Index: test/std/strings/basic.string/string.cons/size_char_alloc.pass.cpp
===================================================================
--- test/std/strings/basic.string/string.cons/size_char_alloc.pass.cpp
+++ test/std/strings/basic.string/string.cons/size_char_alloc.pass.cpp
@@ -15,6 +15,7 @@
 #include <stdexcept>
 #include <algorithm>
 #include <cassert>
+#include <cstddef>
 
 #include "test_macros.h"
 #include "test_allocator.h"
@@ -61,7 +62,7 @@
     typedef typename S::allocator_type A;
     S s2(n, c);
     LIBCPP_ASSERT(s2.__invariants());
-    assert(s2.size() == n);
+    assert(s2.size() == static_cast<std::size_t>(n));
     for (int i = 0; i < n; ++i)
         assert(s2[i] == c);
     assert(s2.get_allocator() == A());
@@ -77,7 +78,7 @@
     typedef typename S::traits_type T;
     S s2(n, c, a);
     LIBCPP_ASSERT(s2.__invariants());
-    assert(s2.size() == n);
+    assert(s2.size() == static_cast<std::size_t>(n));
     for (int i = 0; i < n; ++i)
         assert(s2[i] == c);
     assert(s2.get_allocator() == a);
Index: test/std/strings/basic.string/string.iterators/end.pass.cpp
===================================================================
--- test/std/strings/basic.string/string.iterators/end.pass.cpp
+++ test/std/strings/basic.string/string.iterators/end.pass.cpp
@@ -14,6 +14,7 @@
 
 #include <string>
 #include <cassert>
+#include <cstddef>
 
 #include "min_allocator.h"
 
@@ -29,8 +30,8 @@
         assert(e == s.begin());
         assert(ce == cs.begin());
     }
-    assert(e - s.begin() == s.size());
-    assert(ce - cs.begin() == cs.size());
+    assert(static_cast<std::size_t>(e - s.begin()) == s.size());
+    assert(static_cast<std::size_t>(ce - cs.begin()) == cs.size());
 }
 
 int main()
Index: test/std/strings/basic.string/string.iterators/rend.pass.cpp
===================================================================
--- test/std/strings/basic.string/string.iterators/rend.pass.cpp
+++ test/std/strings/basic.string/string.iterators/rend.pass.cpp
@@ -14,6 +14,7 @@
 
 #include <string>
 #include <cassert>
+#include <cstddef>
 
 #include "min_allocator.h"
 
@@ -29,8 +30,8 @@
         assert(e == s.rbegin());
         assert(ce == cs.rbegin());
     }
-    assert(e - s.rbegin() == s.size());
-    assert(ce - cs.rbegin() == cs.size());
+    assert(static_cast<std::size_t>(e - s.rbegin()) == s.size());
+    assert(static_cast<std::size_t>(ce - cs.rbegin()) == cs.size());
 }
 
 int main()
Index: test/std/strings/string.view/string.view.iterators/end.pass.cpp
===================================================================
--- test/std/strings/string.view/string.view.iterators/end.pass.cpp
+++ test/std/strings/string.view/string.view.iterators/end.pass.cpp
@@ -13,6 +13,7 @@
 
 #include <string_view>
 #include <cassert>
+#include <cstddef>
 
 #include "test_macros.h"
 
@@ -38,9 +39,9 @@
         assert(ce2 !=  s.begin());
     }
 
-    assert(  e -  s.begin() == s.size());
-    assert(ce1 - cs.begin() == cs.size());
-    assert(ce2 - s.cbegin() == s.size());
+    assert(static_cast<std::size_t>(  e -  s.begin()) == s.size());
+    assert(static_cast<std::size_t>(ce1 - cs.begin()) == cs.size());
+    assert(static_cast<std::size_t>(ce2 - s.cbegin()) == s.size());
 
     assert(  e == ce1);
     assert(  e == ce2);
Index: test/std/strings/string.view/string.view.iterators/rend.pass.cpp
===================================================================
--- test/std/strings/string.view/string.view.iterators/rend.pass.cpp
+++ test/std/strings/string.view/string.view.iterators/rend.pass.cpp
@@ -13,6 +13,7 @@
 
 #include <string_view>
 #include <cassert>
+#include <cstddef>
 
 #include "test_macros.h"
 
@@ -38,9 +39,9 @@
         assert(ce2 !=  s.rbegin());
     }
 
-    assert(  e -  s.rbegin() == s.size());
-    assert(ce1 - cs.rbegin() == cs.size());
-    assert(ce2 - s.crbegin() == s.size());
+    assert(static_cast<std::size_t>(  e -  s.rbegin()) == s.size());
+    assert(static_cast<std::size_t>(ce1 - cs.rbegin()) == cs.size());
+    assert(static_cast<std::size_t>(ce2 - s.crbegin()) == s.size());
 
     assert(  e == ce1);
     assert(  e == ce2);