Index: include/__bit_reference
===================================================================
--- include/__bit_reference
+++ include/__bit_reference
@@ -163,7 +163,7 @@
 {
     typedef __bit_iterator<_Cp, _IsConst> _It;
     typedef typename _It::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    static const int __bits_per_word = _It::__bits_per_word;
     // do first partial word
     if (__first.__ctz_ != 0)
     {
@@ -199,7 +199,7 @@
 {
     typedef __bit_iterator<_Cp, _IsConst> _It;
     typedef typename _It::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    static const int __bits_per_word = _It::__bits_per_word;
     // do first partial word
     if (__first.__ctz_ != 0)
     {
@@ -251,7 +251,7 @@
     typedef __bit_iterator<_Cp, _IsConst> _It;
     typedef typename _It::__storage_type __storage_type;
     typedef typename _It::difference_type difference_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    static const int __bits_per_word = _It::__bits_per_word;
     difference_type __r = 0;
     // do first partial word
     if (__first.__ctz_ != 0)
@@ -282,7 +282,7 @@
     typedef __bit_iterator<_Cp, _IsConst> _It;
     typedef typename _It::__storage_type __storage_type;
     typedef typename _It::difference_type difference_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    static const int __bits_per_word = _It::__bits_per_word;
     difference_type __r = 0;
     // do first partial word
     if (__first.__ctz_ != 0)
@@ -324,7 +324,7 @@
 {
     typedef __bit_iterator<_Cp, false> _It;
     typedef typename _It::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    static const int __bits_per_word = _It::__bits_per_word;
     // do first partial word
     if (__first.__ctz_ != 0)
     {
@@ -354,7 +354,7 @@
 {
     typedef __bit_iterator<_Cp, false> _It;
     typedef typename _It::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    static const int __bits_per_word = _It::__bits_per_word;
     // do first partial word
     if (__first.__ctz_ != 0)
     {
@@ -412,7 +412,7 @@
     typedef __bit_iterator<_Cp, _IsConst> _In;
     typedef  typename _In::difference_type difference_type;
     typedef typename _In::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _In::__bits_per_word;
+    static const int __bits_per_word = _In::__bits_per_word;
     difference_type __n = __last - __first;
     if (__n > 0)
     {
@@ -461,7 +461,7 @@
     typedef __bit_iterator<_Cp, _IsConst> _In;
     typedef  typename _In::difference_type difference_type;
     typedef typename _In::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _In::__bits_per_word;
+    static const int __bits_per_word = _In::__bits_per_word;
     difference_type __n = __last - __first;
     if (__n > 0)
     {
@@ -551,7 +551,7 @@
     typedef __bit_iterator<_Cp, _IsConst> _In;
     typedef  typename _In::difference_type difference_type;
     typedef typename _In::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _In::__bits_per_word;
+    static const int __bits_per_word = _In::__bits_per_word;
     difference_type __n = __last - __first;
     if (__n > 0)
     {
@@ -600,7 +600,7 @@
     typedef __bit_iterator<_Cp, _IsConst> _In;
     typedef  typename _In::difference_type difference_type;
     typedef typename _In::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _In::__bits_per_word;
+    static const int __bits_per_word = _In::__bits_per_word;
     difference_type __n = __last - __first;
     if (__n > 0)
     {
@@ -718,7 +718,7 @@
     typedef __bit_iterator<__C1, false> _I1;
     typedef  typename _I1::difference_type difference_type;
     typedef typename _I1::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _I1::__bits_per_word;
+    static const int __bits_per_word = _I1::__bits_per_word;
     difference_type __n = __last - __first;
     if (__n > 0)
     {
@@ -768,7 +768,7 @@
     typedef __bit_iterator<__C1, false> _I1;
     typedef  typename _I1::difference_type difference_type;
     typedef typename _I1::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _I1::__bits_per_word;
+    static const int __bits_per_word = _I1::__bits_per_word;
     difference_type __n = __last - __first;
     if (__n > 0)
     {
@@ -880,7 +880,7 @@
     typedef typename _Cp::__storage_type  __storage_type;
     typedef typename _Cp::__storage_pointer __storage_pointer;
     typedef typename _Cp::iterator        iterator;
-    static const unsigned __bits_per_word = _Cp::__bits_per_word;
+    static const int __bits_per_word = _Cp::__bits_per_word;
     static const unsigned _Np = 4;
 
     difference_type __size_;
@@ -959,7 +959,7 @@
     typedef __bit_iterator<_Cp, _IC1> _It;
     typedef  typename _It::difference_type difference_type;
     typedef typename _It::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    static const int __bits_per_word = _It::__bits_per_word;
     difference_type __n = __last1 - __first1;
     if (__n > 0)
     {
@@ -1041,7 +1041,7 @@
     typedef __bit_iterator<_Cp, _IC1> _It;
     typedef  typename _It::difference_type difference_type;
     typedef typename _It::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    static const int __bits_per_word = _It::__bits_per_word;
     difference_type __n = __last1 - __first1;
     if (__n > 0)
     {
@@ -1101,7 +1101,7 @@
     typedef typename _Cp::__storage_type                                           __storage_type;
     typedef typename conditional<_IsConst, typename _Cp::__const_storage_pointer,
                                            typename _Cp::__storage_pointer>::type  __storage_pointer;
-    static const unsigned __bits_per_word = _Cp::__bits_per_word;
+    static const int __bits_per_word = _Cp::__bits_per_word;
 
     __storage_pointer __seg_;
     unsigned          __ctz_;
Index: include/deque
===================================================================
--- include/deque
+++ include/deque
@@ -2735,7 +2735,7 @@
     difference_type __pos = __f - __b;
     iterator __p = __b + __pos;
     allocator_type& __a = __base::__alloc();
-    if (__pos <= (__base::size() - 1) / 2)
+    if (static_cast<size_type>(__pos) <= (__base::size() - 1) / 2)
     {   // erase from front
         _VSTD::move_backward(__b, __p, _VSTD::next(__p));
         __alloc_traits::destroy(__a, _VSTD::addressof(*__b));
Index: include/istream
===================================================================
--- include/istream
+++ include/istream
@@ -1651,7 +1651,7 @@
             ios_base::iostate __err = ios_base::goodbit;
             _CharT __zero = __ct.widen('0');
             _CharT __one = __ct.widen('1');
-            while (__c < _Size)
+            while (static_cast<size_t>(__c) < _Size)
             {
                 typename _Traits::int_type __i = __is.rdbuf()->sgetc();
                 if (_Traits::eq_int_type(__i, _Traits::eof()))
Index: include/random
===================================================================
--- include/random
+++ include/random
@@ -2918,7 +2918,7 @@
 typename discard_block_engine<_Engine, __p, __r>::result_type
 discard_block_engine<_Engine, __p, __r>::operator()()
 {
-    if (__n_ >= __r)
+    if (__n_ >= 0 && static_cast<size_t>(__n_) >= __r)
     {
         __e_.discard(__p - __r);
         __n_ = 0;
Index: include/regex
===================================================================
--- include/regex
+++ include/regex
@@ -6420,7 +6420,8 @@
     _Position __prev = __position_;
     if (__result_ == &__suffix_)
         __result_ = nullptr;
-    else if (_N_ + 1 < __subs_.size())
+    // _N_ should always be positive
+    else if (static_cast<size_t>(_N_) + 1 < __subs_.size())
     {
         ++_N_;
         __establish_result();
Index: include/vector
===================================================================
--- include/vector
+++ include/vector
@@ -2914,7 +2914,9 @@
 vector<bool, _Allocator>::assign(_ForwardIterator __first, _ForwardIterator __last)
 {
     clear();
-    difference_type __n = _VSTD::distance(__first, __last);
+    const difference_type __ns = _VSTD::distance(__first, __last);
+    _LIBCPP_ASSERT(__ns >= 0, "invalid range specified");
+    const size_type __n = static_cast<size_type>(__ns);
     if (__n)
     {
         if (__n > capacity())
Index: test/libcxx/test/config.py
===================================================================
--- test/libcxx/test/config.py
+++ test/libcxx/test/config.py
@@ -660,7 +660,7 @@
             # team using the test suite; They enable the warnings below and
             # expect the test suite to be clean.
             # FIXME: Re-enable this after fixing remaining occurrences.
-            self.cxx.addWarningFlagIfSupported('-Wno-sign-compare')
+            self.cxx.addWarningFlagIfSupported('-Wsign-compare')
             # FIXME: Enable the two warnings below.
             self.cxx.addWarningFlagIfSupported('-Wno-unused-variable')
             self.cxx.addWarningFlagIfSupported('-Wno-unused-parameter')