Index: include/locale
===================================================================
--- include/locale
+++ include/locale
@@ -191,8 +191,18 @@
 #endif
 #include <cstdlib>
 #include <ctime>
+
+#ifndef __has_include
+#define __has_include(x) 0
+#endif
+#if __has_include(<newlib.h>)
+#include <newlib.h> // for _NEWLIB_VERSION
+#endif
+
 #if defined(_LIBCPP_MSVCRT) || defined(__MINGW32__)
 #include <support/win32/locale_win32.h>
+#elif defined(_NEWLIB_VERSION)
+#include <support/newlib/xlocale.h>
 #elif !defined(__ANDROID__)
 #include <nl_types.h>
 #endif
@@ -229,7 +239,8 @@
 // OSX has nice foo_l() functions that let you turn off use of the global
 // locale.  Linux, not so much.  The following functions avoid the locale when
 // that's possible and otherwise do the wrong thing.  FIXME.
-#if defined(__linux__) || defined(__EMSCRIPTEN__) || defined(_AIX)
+#if defined(__linux__) || defined(__EMSCRIPTEN__) || defined(_AIX) || \
+    defined(_NEWLIB_VERSION)
 
 #ifdef _LIBCPP_LOCALE__L_EXTENSIONS
 decltype(MB_CUR_MAX_L(_VSTD::declval<locale_t>()))
@@ -3673,7 +3684,7 @@
 typename messages<_CharT>::catalog
 messages<_CharT>::do_open(const basic_string<char>& __nm, const locale&) const
 {
-#if defined(_WIN32) || defined(__ANDROID__)
+#if defined(_WIN32) || defined(__ANDROID__) || defined(_NEWLIB_VERSION)
     return -1;
 #else // _WIN32 || __ANDROID__
     catalog __cat = (catalog)catopen(__nm.c_str(), NL_CAT_LOCALE);
@@ -3688,7 +3699,7 @@
 messages<_CharT>::do_get(catalog __c, int __set, int __msgid,
                          const string_type& __dflt) const
 {
-#if defined(_WIN32) || defined(__ANDROID__)
+#if defined(_WIN32) || defined(__ANDROID__) || defined(_NEWLIB_VERSION)
     return __dflt;
 #else // _WIN32
     string __ndflt;
@@ -3710,7 +3721,7 @@
 void
 messages<_CharT>::do_close(catalog __c) const
 {
-#if !defined(_WIN32) && !defined(__ANDROID__)
+#if !defined(_WIN32) && !defined(__ANDROID__) && !defined(_NEWLIB_VERSION)
     if (__c != -1)
         __c <<= 1;
     nl_catd __cat = (nl_catd)__c;
Index: include/support/newlib/xlocale.h
===================================================================
--- include/support/newlib/xlocale.h
+++ include/support/newlib/xlocale.h
@@ -0,0 +1,72 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_SUPPORT_NEWLIB_XLOCALE_H
+#define _LIBCPP_SUPPORT_NEWLIB_XLOCALE_H
+
+#if defined(_NEWLIB_VERSION)
+
+#include <cstdlib>
+#include <clocale>
+#include <cwctype>
+#include <ctype.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+#if defined(__STRICT_ANSI__)
+// TODO(jroelofs): so newlib has this, but it's guarded out in c++. Would it be
+// better to put the declaration for that here?
+static inline int isascii(int c) {
+    return (0 <= c && c <= 127) ? 1 : 0;
+}
+#endif
+
+// Patch over newlib's lack of extended locale support
+typedef void *locale_t;
+static inline locale_t duplocale(locale_t) {
+  return nullptr;
+}
+
+static inline void freelocale(locale_t) {
+}
+
+static inline locale_t newlocale(int, const char *, locale_t) {
+  return nullptr;
+}
+
+static inline locale_t uselocale(locale_t) {
+  return nullptr;
+}
+
+#define LC_COLLATE_MASK (1 << LC_COLLATE)
+#define LC_CTYPE_MASK (1 << LC_CTYPE)
+#define LC_MESSAGES_MASK (1 << LC_MESSAGES)
+#define LC_MONETARY_MASK (1 << LC_MONETARY)
+#define LC_NUMERIC_MASK (1 << LC_NUMERIC)
+#define LC_TIME_MASK (1 << LC_TIME)
+#define LC_ALL_MASK (LC_COLLATE_MASK|\
+                     LC_CTYPE_MASK|\
+                     LC_MONETARY_MASK|\
+                     LC_NUMERIC_MASK|\
+                     LC_TIME_MASK|\
+                     LC_MESSAGES_MASK)
+
+// TODO(jroelofs): I hate '..' in include lines. Is there a better way?
+#include <support/xlocale/xlocale.h>
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif // _NEWLIB_VERSION
+
+#endif
Index: include/support/xlocale/xlocale.h
===================================================================
--- include/support/xlocale/xlocale.h
+++ include/support/xlocale/xlocale.h
@@ -0,0 +1,194 @@
+// -*- C++ -*-
+//===------------------- support/xlocale/xlocale.h ------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// This is a shared implementation of a shim to provide extended locale support
+// on top of libc's that don't support it (like Android's bionic, and Newlib).
+//
+// The 'illusion' only works when the specified locale is "C" or "POSIX", but
+// that's about as good as we can do without implementing full xlocale support
+// in the underlying libc.
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_SUPPORT_XLOCALE_XLOCALE_H
+#define _LIBCPP_SUPPORT_XLOCALE_XLOCALE_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static inline int isalnum_l(int c, locale_t) {
+  return isalnum(c);
+}
+
+static inline int isalpha_l(int c, locale_t) {
+  return isalpha(c);
+}
+
+static inline int isblank_l(int c, locale_t) {
+  return isblank(c);
+}
+
+static inline int iscntrl_l(int c, locale_t) {
+  return iscntrl(c);
+}
+
+static inline int isdigit_l(int c, locale_t) {
+  return isdigit(c);
+}
+
+static inline int isgraph_l(int c, locale_t) {
+  return isgraph(c);
+}
+
+static inline int islower_l(int c, locale_t) {
+  return islower(c);
+}
+
+static inline int isprint_l(int c, locale_t) {
+  return isprint(c);
+}
+
+static inline int ispunct_l(int c, locale_t) {
+  return ispunct(c);
+}
+
+static inline int isspace_l(int c, locale_t) {
+  return isspace(c);
+}
+
+static inline int isupper_l(int c, locale_t) {
+  return isupper(c);
+}
+
+static inline int isxdigit_l(int c, locale_t) {
+  return isxdigit(c);
+}
+
+static inline int iswalnum_l(wint_t c, locale_t) {
+  return iswalnum(c);
+}
+
+static inline int iswalpha_l(wint_t c, locale_t) {
+  return iswalpha(c);
+}
+
+static inline int iswblank_l(wint_t c, locale_t) {
+  return iswblank(c);
+}
+
+static inline int iswcntrl_l(wint_t c, locale_t) {
+  return iswcntrl(c);
+}
+
+static inline int iswdigit_l(wint_t c, locale_t) {
+  return iswdigit(c);
+}
+
+static inline int iswgraph_l(wint_t c, locale_t) {
+  return iswgraph(c);
+}
+
+static inline int iswlower_l(wint_t c, locale_t) {
+  return iswlower(c);
+}
+
+static inline int iswprint_l(wint_t c, locale_t) {
+  return iswprint(c);
+}
+
+static inline int iswpunct_l(wint_t c, locale_t) {
+  return iswpunct(c);
+}
+
+static inline int iswspace_l(wint_t c, locale_t) {
+  return iswspace(c);
+}
+
+static inline int iswupper_l(wint_t c, locale_t) {
+  return iswupper(c);
+}
+
+static inline int iswxdigit_l(wint_t c, locale_t) {
+  return iswxdigit(c);
+}
+
+static inline int toupper_l(int c, locale_t) {
+  return toupper(c);
+}
+
+static inline int tolower_l(int c, locale_t) {
+  return tolower(c);
+}
+
+static inline int towupper_l(int c, locale_t) {
+  return towupper(c);
+}
+
+static inline int towlower_l(int c, locale_t) {
+  return towlower(c);
+}
+
+static inline int strcoll_l(const char *s1, const char *s2, locale_t) {
+  return strcoll(s1, s2);
+}
+
+static inline size_t strxfrm_l(char *dest, const char *src, size_t n,
+                               locale_t) {
+  return strxfrm(dest, src, n);
+}
+
+static inline size_t strftime_l(char *s, size_t max, const char *format,
+                                const struct tm *tm, locale_t) {
+  return strftime(s, max, format, tm);
+}
+
+static inline int wcscoll_l(const wchar_t *ws1, const wchar_t *ws2, locale_t) {
+  return wcscoll(ws1, ws2);
+}
+
+static inline size_t wcsxfrm_l(wchar_t *dest, const wchar_t *src, size_t n,
+                               locale_t) {
+  return wcsxfrm(dest, src, n);
+}
+
+static inline long double strtold_l(const char *nptr, char **endptr, locale_t) {
+  return strtold(nptr, endptr);
+}
+
+static inline long long strtoll_l(const char *nptr, char **endptr, int base,
+                                  locale_t) {
+  return strtoll(nptr, endptr, base);
+}
+
+static inline unsigned long long strtoull_l(const char *nptr, char **endptr,
+                                            int base, locale_t) {
+  return strtoull(nptr, endptr, base);
+}
+
+static inline long long wcstoll_l(const wchar_t *nptr, wchar_t **endptr,
+                                  int base, locale_t) {
+  return wcstoll(nptr, endptr, base);
+}
+
+static inline unsigned long long wcstoull_l(const wchar_t *nptr,
+                                            wchar_t **endptr, int base,
+                                            locale_t) {
+  return wcstoull(nptr, endptr, base);
+}
+
+static inline long double wcstold_l(const wchar_t *nptr, wchar_t **endptr,
+                                    locale_t) {
+  return wcstold(nptr, endptr);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // _LIBCPP_SUPPORT_XLOCALE_XLOCALE_H