diff --git a/libcxx/include/__hash_table b/libcxx/include/__hash_table
--- a/libcxx/include/__hash_table
+++ b/libcxx/include/__hash_table
@@ -1571,7 +1571,7 @@
             {
                 (*__p)->__c_ = nullptr;
                 if (--__c->end_ != __p)
-                    memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
+                    _VSTD::memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
             }
         }
         __get_db()->unlock();
@@ -2599,7 +2599,7 @@
         {
             (*__dp)->__c_ = nullptr;
             if (--__c->end_ != __dp)
-                memmove(__dp, __dp+1, (__c->end_ - __dp)*sizeof(__i_node*));
+                _VSTD::memmove(__dp, __dp+1, (__c->end_ - __dp)*sizeof(__i_node*));
         }
     }
     __get_db()->unlock();
diff --git a/libcxx/include/__locale b/libcxx/include/__locale
--- a/libcxx/include/__locale
+++ b/libcxx/include/__locale
@@ -79,7 +79,7 @@
       // locale name, otherwise it will be a semicolon-separated string listing
       // each category.  In the second case, we know at least one category won't
       // be what we want, so we only have to check the first case.
-      if (strcmp(__l.__get_locale(), __lc) != 0) {
+      if (_VSTD::strcmp(__l.__get_locale(), __lc) != 0) {
         __locale_all = _strdup(__lc);
         if (__locale_all == nullptr)
           __throw_bad_alloc();
diff --git a/libcxx/include/__string b/libcxx/include/__string
--- a/libcxx/include/__string
+++ b/libcxx/include/__string
@@ -55,7 +55,9 @@
 
 #include <__config>
 #include <algorithm>  // for search and min
-#include <cstdio>     // For EOF.
+#include <cstdio>     // for EOF
+#include <cstring>    // for memcpy
+#include <cwchar>     // for wmemcpy
 #include <memory>     // for __murmur2_or_cityhash
 
 #include <__debug>
@@ -375,7 +377,7 @@
         {
             return __libcpp_is_constant_evaluated()
                        ? _VSTD::__move_constexpr(__s1, __s2, __n)
-                       : __n == 0 ? __s1 : (char_type*)memmove(__s1, __s2, __n);
+                       : __n == 0 ? __s1 : (char_type*)_VSTD::memmove(__s1, __s2, __n);
         }
     static inline _LIBCPP_CONSTEXPR_AFTER_CXX17
     char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
@@ -383,14 +385,14 @@
             _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
             return __libcpp_is_constant_evaluated()
                        ? _VSTD::__copy_constexpr(__s1, __s2, __n)
-                       : __n == 0 ? __s1 : (char_type*)memcpy(__s1, __s2, __n);
+                       : __n == 0 ? __s1 : (char_type*)_VSTD::memcpy(__s1, __s2, __n);
         }
     static inline _LIBCPP_CONSTEXPR_AFTER_CXX17
     char_type* assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT
         {
             return __libcpp_is_constant_evaluated()
                        ? _VSTD::__assign_constexpr(__s, __n, __a)
-                       : __n == 0 ? __s : (char_type*)memset(__s, to_int_type(__a), __n);
+                       : __n == 0 ? __s : (char_type*)_VSTD::memset(__s, to_int_type(__a), __n);
         }
 
     static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
@@ -414,7 +416,7 @@
 #if __has_feature(cxx_constexpr_string_builtins)
     return __builtin_memcmp(__s1, __s2, __n);
 #elif _LIBCPP_STD_VER <= 14
-    return memcmp(__s1, __s2, __n);
+    return _VSTD::memcmp(__s1, __s2, __n);
 #else
     for (; __n; --__n, ++__s1, ++__s2)
     {
@@ -436,7 +438,7 @@
 #if __has_feature(cxx_constexpr_string_builtins)
     return __builtin_char_memchr(__s, to_int_type(__a), __n);
 #elif _LIBCPP_STD_VER <= 14
-    return (const char_type*) memchr(__s, to_int_type(__a), __n);
+    return (const char_type*) _VSTD::memchr(__s, to_int_type(__a), __n);
 #else
     for (; __n; --__n)
     {
@@ -478,7 +480,7 @@
         {
             return __libcpp_is_constant_evaluated()
                        ? _VSTD::__move_constexpr(__s1, __s2, __n)
-                       : __n == 0 ? __s1 : wmemmove(__s1, __s2, __n);
+                       : __n == 0 ? __s1 : _VSTD::wmemmove(__s1, __s2, __n);
         }
     static inline _LIBCPP_CONSTEXPR_AFTER_CXX17
     char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
@@ -486,14 +488,14 @@
             _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
             return __libcpp_is_constant_evaluated()
                        ? _VSTD::__copy_constexpr(__s1, __s2, __n)
-                       : __n == 0 ? __s1 : wmemcpy(__s1, __s2, __n);
+                       : __n == 0 ? __s1 : _VSTD::wmemcpy(__s1, __s2, __n);
         }
     static inline _LIBCPP_CONSTEXPR_AFTER_CXX17
     char_type* assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT
         {
             return __libcpp_is_constant_evaluated()
                        ? _VSTD::__assign_constexpr(__s, __n, __a)
-                       : __n == 0 ? __s : wmemset(__s, __a, __n);
+                       : __n == 0 ? __s : _VSTD::wmemset(__s, __a, __n);
         }
     static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
         {return eq_int_type(__c, eof()) ? ~eof() : __c;}
@@ -516,7 +518,7 @@
 #if __has_feature(cxx_constexpr_string_builtins)
     return __builtin_wmemcmp(__s1, __s2, __n);
 #elif _LIBCPP_STD_VER <= 14
-    return wmemcmp(__s1, __s2, __n);
+    return _VSTD::wmemcmp(__s1, __s2, __n);
 #else
     for (; __n; --__n, ++__s1, ++__s2)
     {
@@ -548,7 +550,7 @@
 #if __has_feature(cxx_constexpr_string_builtins)
     return __builtin_wcslen(__s);
 #elif _LIBCPP_STD_VER <= 14
-    return wcslen(__s);
+    return _VSTD::wcslen(__s);
 #else
     size_t __len = 0;
     for (; !eq(*__s, char_type(0)); ++__s)
@@ -566,7 +568,7 @@
 #if __has_feature(cxx_constexpr_string_builtins)
     return __builtin_wmemchr(__s, __a, __n);
 #elif _LIBCPP_STD_VER <= 14
-    return wmemchr(__s, __a, __n);
+    return _VSTD::wmemchr(__s, __a, __n);
 #else
     for (; __n; --__n)
     {
@@ -611,7 +613,7 @@
         {
             return __libcpp_is_constant_evaluated()
                        ? _VSTD::__move_constexpr(__s1, __s2, __n)
-                       : __n == 0 ? __s1 : (char_type*)memmove(__s1, __s2, __n);
+                       : __n == 0 ? __s1 : (char_type*)_VSTD::memmove(__s1, __s2, __n);
         }
 
     static _LIBCPP_CONSTEXPR_AFTER_CXX17
@@ -620,7 +622,7 @@
             _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
             return __libcpp_is_constant_evaluated()
                        ? _VSTD::__copy_constexpr(__s1, __s2, __n)
-                       : __n == 0 ? __s1 : (char_type*)memcpy(__s1, __s2, __n);
+                       : __n == 0 ? __s1 : (char_type*)_VSTD::memcpy(__s1, __s2, __n);
         }
 
     static _LIBCPP_CONSTEXPR_AFTER_CXX17
@@ -628,7 +630,7 @@
         {
             return __libcpp_is_constant_evaluated()
                        ? _VSTD::__assign_constexpr(__s, __n, __a)
-                       : __n == 0 ? __s : (char_type*)memset(__s, to_int_type(__a), __n);
+                       : __n == 0 ? __s : (char_type*)_VSTD::memset(__s, to_int_type(__a), __n);
         }
 
     static inline constexpr int_type  not_eof(int_type __c) noexcept
diff --git a/libcxx/include/atomic b/libcxx/include/atomic
--- a/libcxx/include/atomic
+++ b/libcxx/include/atomic
@@ -662,7 +662,7 @@
 
 template <typename _Tp> _LIBCPP_INLINE_VISIBILITY
 bool __cxx_nonatomic_compare_equal(_Tp const& __lhs, _Tp const& __rhs) {
-    return memcmp(&__lhs, &__rhs, sizeof(_Tp)) == 0;
+    return _VSTD::memcmp(&__lhs, &__rhs, sizeof(_Tp)) == 0;
 }
 
 static_assert((is_same<underlying_type<memory_order>::type, __memory_order_underlying_t>::value),
@@ -1262,7 +1262,7 @@
   _Tp __temp;
   __a->__lock();
   __cxx_atomic_assign_volatile(__temp, __a->__a_value);
-  bool __ret = (memcmp(&__temp, __expected, sizeof(_Tp)) == 0);
+  bool __ret = (_VSTD::memcmp(&__temp, __expected, sizeof(_Tp)) == 0);
   if(__ret)
     __cxx_atomic_assign_volatile(__a->__a_value, __value);
   else
@@ -1275,11 +1275,11 @@
 bool __cxx_atomic_compare_exchange_strong(__cxx_atomic_lock_impl<_Tp>* __a,
                                           _Tp* __expected, _Tp __value, memory_order, memory_order) {
   __a->__lock();
-  bool __ret = (memcmp(&__a->__a_value, __expected, sizeof(_Tp)) == 0);
+  bool __ret = (_VSTD::memcmp(&__a->__a_value, __expected, sizeof(_Tp)) == 0);
   if(__ret)
-    memcpy(&__a->__a_value, &__value, sizeof(_Tp));
+    _VSTD::memcpy(&__a->__a_value, &__value, sizeof(_Tp));
   else
-    memcpy(__expected, &__a->__a_value, sizeof(_Tp));
+    _VSTD::memcpy(__expected, &__a->__a_value, sizeof(_Tp));
   __a->__unlock();
   return __ret;
 }
@@ -1291,7 +1291,7 @@
   _Tp __temp;
   __a->__lock();
   __cxx_atomic_assign_volatile(__temp, __a->__a_value);
-  bool __ret = (memcmp(&__temp, __expected, sizeof(_Tp)) == 0);
+  bool __ret = (_VSTD::memcmp(&__temp, __expected, sizeof(_Tp)) == 0);
   if(__ret)
     __cxx_atomic_assign_volatile(__a->__a_value, __value);
   else
@@ -1304,11 +1304,11 @@
 bool __cxx_atomic_compare_exchange_weak(__cxx_atomic_lock_impl<_Tp>* __a,
                                         _Tp* __expected, _Tp __value, memory_order, memory_order) {
   __a->__lock();
-  bool __ret = (memcmp(&__a->__a_value, __expected, sizeof(_Tp)) == 0);
+  bool __ret = (_VSTD::memcmp(&__a->__a_value, __expected, sizeof(_Tp)) == 0);
   if(__ret)
-    memcpy(&__a->__a_value, &__value, sizeof(_Tp));
+    _VSTD::memcpy(&__a->__a_value, &__value, sizeof(_Tp));
   else
-    memcpy(__expected, &__a->__a_value, sizeof(_Tp));
+    _VSTD::memcpy(__expected, &__a->__a_value, sizeof(_Tp));
   __a->__unlock();
   return __ret;
 }
diff --git a/libcxx/include/charconv b/libcxx/include/charconv
--- a/libcxx/include/charconv
+++ b/libcxx/include/charconv
@@ -333,7 +333,7 @@
         auto __len = __p - __buf;
         if (__len <= __diff)
         {
-            memcpy(__first, __buf, __len);
+            _VSTD::memcpy(__first, __buf, __len);
             return {__first + __len, {}};
         }
         else
@@ -382,7 +382,7 @@
         return {__last, errc::value_too_large};
     else
     {
-        memmove(__first, __p, __len);
+        _VSTD::memmove(__first, __p, __len);
         return {__first + __len, {}};
     }
 }
@@ -429,7 +429,7 @@
         if (__x <= __complement(__to_unsigned(__tl::min())))
         {
             __x = __complement(__x);
-            memcpy(&__value, &__x, sizeof(__x));
+            _VSTD::memcpy(&__value, &__x, sizeof(__x));
             return __r;
         }
     }
diff --git a/libcxx/include/fstream b/libcxx/include/fstream
--- a/libcxx/include/fstream
+++ b/libcxx/include/fstream
@@ -721,7 +721,7 @@
     int_type __c = traits_type::eof();
     if (this->gptr() == this->egptr())
     {
-        memmove(this->eback(), this->egptr() - __unget_sz, __unget_sz * sizeof(char_type));
+        _VSTD::memmove(this->eback(), this->egptr() - __unget_sz, __unget_sz * sizeof(char_type));
         if (__always_noconv_)
         {
             size_t __nmemb = static_cast<size_t>(this->egptr() - this->eback() - __unget_sz);
@@ -738,7 +738,7 @@
         {
             _LIBCPP_ASSERT ( !(__extbufnext_ == NULL && (__extbufend_ != __extbufnext_)), "underflow moving from NULL" );
             if (__extbufend_ != __extbufnext_)
-                memmove(__extbuf_, __extbufnext_, __extbufend_ - __extbufnext_);
+                _VSTD::memmove(__extbuf_, __extbufnext_, __extbufend_ - __extbufnext_);
             __extbufnext_ = __extbuf_ + (__extbufend_ - __extbufnext_);
             __extbufend_ = __extbuf_ + (__extbuf_ == __extbuf_min_ ? sizeof(__extbuf_min_) : __ebs_);
             size_t __nmemb = _VSTD::min(static_cast<size_t>(__ibs_ - __unget_sz),
diff --git a/libcxx/include/list b/libcxx/include/list
--- a/libcxx/include/list
+++ b/libcxx/include/list
@@ -810,7 +810,7 @@
         {
             __cn2->__add(*__p);
             if (--__cn1->end_ != __p)
-                memmove(__p, __p+1, (__cn1->end_ - __p)*sizeof(__i_node*));
+                _VSTD::memmove(__p, __p+1, (__cn1->end_ - __p)*sizeof(__i_node*));
         }
         else
             (*__p)->__c_ = __cn1;
@@ -823,7 +823,7 @@
         {
             __cn1->__add(*__p);
             if (--__cn2->end_ != __p)
-                memmove(__p, __p+1, (__cn2->end_ - __p)*sizeof(__i_node*));
+                _VSTD::memmove(__p, __p+1, (__cn2->end_ - __p)*sizeof(__i_node*));
         }
         else
             (*__p)->__c_ = __cn2;
@@ -1758,7 +1758,7 @@
         {
             (*__p)->__c_ = nullptr;
             if (--__c->end_ != __p)
-                memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
+                _VSTD::memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
         }
     }
     __get_db()->unlock();
@@ -1787,7 +1787,7 @@
         {
             (*__p)->__c_ = nullptr;
             if (--__c->end_ != __p)
-                memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
+                _VSTD::memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
         }
     }
     __get_db()->unlock();
@@ -1823,7 +1823,7 @@
         {
             (*__ip)->__c_ = nullptr;
             if (--__c->end_ != __ip)
-                memmove(__ip, __ip+1, (__c->end_ - __ip)*sizeof(__i_node*));
+                _VSTD::memmove(__ip, __ip+1, (__c->end_ - __ip)*sizeof(__i_node*));
         }
     }
     __get_db()->unlock();
@@ -1869,7 +1869,7 @@
                 {
                     (*__p)->__c_ = nullptr;
                     if (--__c->end_ != __p)
-                        memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
+                        _VSTD::memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
                 }
             }
             __get_db()->unlock();
@@ -2034,7 +2034,7 @@
                     __cn1->__add(*__ip);
                     (*__ip)->__c_ = __cn1;
                     if (--__cn2->end_ != __ip)
-                        memmove(__ip, __ip+1, (__cn2->end_ - __ip)*sizeof(__i_node*));
+                        _VSTD::memmove(__ip, __ip+1, (__cn2->end_ - __ip)*sizeof(__i_node*));
                 }
             }
             __db->unlock();
@@ -2079,7 +2079,7 @@
                     __cn1->__add(*__ip);
                     (*__ip)->__c_ = __cn1;
                     if (--__cn2->end_ != __ip)
-                        memmove(__ip, __ip+1, (__cn2->end_ - __ip)*sizeof(__i_node*));
+                        _VSTD::memmove(__ip, __ip+1, (__cn2->end_ - __ip)*sizeof(__i_node*));
                 }
             }
             __db->unlock();
@@ -2138,7 +2138,7 @@
                         __cn1->__add(*__ip);
                         (*__ip)->__c_ = __cn1;
                         if (--__cn2->end_ != __ip)
-                            memmove(__ip, __ip+1, (__cn2->end_ - __ip)*sizeof(__i_node*));
+                            _VSTD::memmove(__ip, __ip+1, (__cn2->end_ - __ip)*sizeof(__i_node*));
                     }
                 }
             }
@@ -2271,7 +2271,7 @@
                 __cn1->__add(*__p);
                 (*__p)->__c_ = __cn1;
                 if (--__cn2->end_ != __p)
-                    memmove(__p, __p+1, (__cn2->end_ - __p)*sizeof(__i_node*));
+                    _VSTD::memmove(__p, __p+1, (__cn2->end_ - __p)*sizeof(__i_node*));
             }
         }
         __db->unlock();
diff --git a/libcxx/include/locale b/libcxx/include/locale
--- a/libcxx/include/locale
+++ b/libcxx/include/locale
@@ -3578,7 +3578,7 @@
     char* __n = catgets(__cat, __set, __msgid, __ndflt.c_str());
     string_type __w;
     __widen_from_utf8<sizeof(char_type)*__CHAR_BIT__>()(back_inserter(__w),
-                                                        __n, __n + strlen(__n));
+                                                        __n, __n + _VSTD::strlen(__n));
     return __w;
 #else // !_LIBCPP_HAS_CATOPEN
     _LIBCPP_UNUSED_VAR(__c);
@@ -3999,7 +3999,7 @@
     int_type __c = traits_type::eof();
     if (this->gptr() == this->egptr())
     {
-        memmove(this->eback(), this->egptr() - __unget_sz, __unget_sz * sizeof(char_type));
+        _VSTD::memmove(this->eback(), this->egptr() - __unget_sz, __unget_sz * sizeof(char_type));
         if (__always_noconv_)
         {
             streamsize __nmemb = static_cast<streamsize>(this->egptr() - this->eback() - __unget_sz);
@@ -4016,7 +4016,7 @@
         {
              _LIBCPP_ASSERT(!(__extbufnext_ == NULL && (__extbufend_ != __extbufnext_)), "underflow moving from NULL" );
              if (__extbufend_ != __extbufnext_)
-                memmove(__extbuf_, __extbufnext_, __extbufend_ - __extbufnext_);
+                _VSTD::memmove(__extbuf_, __extbufnext_, __extbufend_ - __extbufnext_);
             __extbufnext_ = __extbuf_ + (__extbufend_ - __extbufnext_);
             __extbufend_ = __extbuf_ + (__extbuf_ == __extbuf_min_ ? sizeof(__extbuf_min_) : __ebs_);
             streamsize __nmemb = _VSTD::min(static_cast<streamsize>(this->egptr() - this->eback() - __unget_sz),
diff --git a/libcxx/include/string b/libcxx/include/string
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -1774,7 +1774,7 @@
             {
                 (*__p)->__c_ = nullptr;
                 if (--__c->end_ != __p)
-                    memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
+                    _VSTD::memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
             }
         }
         __get_db()->unlock();
diff --git a/libcxx/include/strstream b/libcxx/include/strstream
--- a/libcxx/include/strstream
+++ b/libcxx/include/strstream
@@ -290,7 +290,7 @@
     _LIBCPP_INLINE_VISIBILITY
     ostrstream(char* __s, int __n, ios_base::openmode __mode = ios_base::out)
         : ostream(&__sb_),
-          __sb_(__s, __n, __s + (__mode & ios::app ? strlen(__s) : 0))
+          __sb_(__s, __n, __s + (__mode & ios::app ? _VSTD::strlen(__s) : 0))
         {}
 
 #ifndef _LIBCPP_CXX03_LANG
@@ -350,7 +350,7 @@
     _LIBCPP_INLINE_VISIBILITY
     strstream(char* __s, int __n, ios_base::openmode __mode = ios_base::in | ios_base::out)
         : iostream(&__sb_),
-          __sb_(__s, __n, __s + (__mode & ios::app ? strlen(__s) : 0))
+          __sb_(__s, __n, __s + (__mode & ios::app ? _VSTD::strlen(__s) : 0))
         {}
 
 #ifndef _LIBCPP_CXX03_LANG
diff --git a/libcxx/include/vector b/libcxx/include/vector
--- a/libcxx/include/vector
+++ b/libcxx/include/vector
@@ -2139,7 +2139,7 @@
     if (__i->base() > __new_last) {
       (*__p)->__c_ = nullptr;
       if (--__c->end_ != __p)
-        memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
+        _VSTD::memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
     }
   }
   __get_db()->unlock();