diff -Nur gcc-4.9.3.orig/libstdc++-v3/config/locale/generic/c_locale.h gcc-4.9.3/libstdc++-v3/config/locale/generic/c_locale.h
--- gcc-4.9.3.orig/libstdc++-v3/config/locale/generic/c_locale.h	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/config/locale/generic/c_locale.h	2015-06-30 05:09:31.000000000 +0200
@@ -70,7 +70,7 @@
     __builtin_va_list __args;
     __builtin_va_start(__args, __fmt);
 
-#ifdef _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
     const int __ret = __builtin_vsnprintf(__out, __size, __fmt, __args);
 #else
     const int __ret = __builtin_vsprintf(__out, __fmt, __args);
diff -Nur gcc-4.9.3.orig/libstdc++-v3/config/locale/gnu/c_locale.h gcc-4.9.3/libstdc++-v3/config/locale/gnu/c_locale.h
--- gcc-4.9.3.orig/libstdc++-v3/config/locale/gnu/c_locale.h	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/config/locale/gnu/c_locale.h	2015-06-30 05:09:31.000000000 +0200
@@ -88,7 +88,7 @@
     __builtin_va_list __args;
     __builtin_va_start(__args, __fmt);
 
-#ifdef _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
     const int __ret = __builtin_vsnprintf(__out, __size, __fmt, __args);
 #else
     const int __ret = __builtin_vsprintf(__out, __fmt, __args);
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/bits/basic_string.h gcc-4.9.3/libstdc++-v3/include/bits/basic_string.h
--- gcc-4.9.3.orig/libstdc++-v3/include/bits/basic_string.h	2015-05-28 18:27:46.000000000 +0200
+++ gcc-4.9.3/libstdc++-v3/include/bits/basic_string.h	2015-06-30 05:12:40.000000000 +0200
@@ -2844,7 +2844,7 @@
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
 
-#if __cplusplus >= 201103L && defined(_GLIBCXX_USE_C99)
+#if __cplusplus >= 201103L && (defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__))
 
 #include <ext/string_conversions.h>
 
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/bits/locale_facets_nonio.tcc gcc-4.9.3/libstdc++-v3/include/bits/locale_facets_nonio.tcc
--- gcc-4.9.3.orig/libstdc++-v3/include/bits/locale_facets_nonio.tcc	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/include/bits/locale_facets_nonio.tcc	2015-06-30 05:09:32.000000000 +0200
@@ -572,7 +572,7 @@
     {
       const locale __loc = __io.getloc();
       const ctype<_CharT>& __ctype = use_facet<ctype<_CharT> >(__loc);
-#ifdef _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
       // First try a buffer perhaps big enough.
       int __cs_size = 64;
       char* __cs = static_cast<char*>(__builtin_alloca(__cs_size));
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/bits/locale_facets.tcc gcc-4.9.3/libstdc++-v3/include/bits/locale_facets.tcc
--- gcc-4.9.3.orig/libstdc++-v3/include/bits/locale_facets.tcc	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/include/bits/locale_facets.tcc	2015-06-30 05:09:32.000000000 +0200
@@ -987,7 +987,7 @@
 	char __fbuf[16];
 	__num_base::_S_format_float(__io, __fbuf, __mod);
 
-#ifdef _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
 	// First try a buffer perhaps big enough (most probably sufficient
 	// for non-ios_base::fixed outputs)
 	int __cs_size = __max_digits * 3;
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/c_compatibility/math.h gcc-4.9.3/libstdc++-v3/include/c_compatibility/math.h
--- gcc-4.9.3.orig/libstdc++-v3/include/c_compatibility/math.h	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/include/c_compatibility/math.h	2015-06-30 05:09:32.000000000 +0200
@@ -56,7 +56,7 @@
 using std::floor;
 using std::fmod;
 
-#if _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
 using std::fpclassify;
 using std::isfinite;
 using std::isinf;
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/c_compatibility/wchar.h gcc-4.9.3/libstdc++-v3/include/c_compatibility/wchar.h
--- gcc-4.9.3.orig/libstdc++-v3/include/c_compatibility/wchar.h	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/include/c_compatibility/wchar.h	2015-06-30 05:09:32.000000000 +0200
@@ -103,7 +103,7 @@
 using std::wmemset;
 using std::wcsftime;
 
-#if _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
 using std::wcstold;
 using std::wcstoll;
 using std::wcstoull;
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/c_global/cstdio gcc-4.9.3/libstdc++-v3/include/c_global/cstdio
--- gcc-4.9.3.orig/libstdc++-v3/include/c_global/cstdio	2014-01-23 22:17:15.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/include/c_global/cstdio	2015-06-30 05:09:32.000000000 +0200
@@ -146,7 +146,7 @@
   using ::vsprintf;
 } // namespace
 
-#if _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
 
 #undef snprintf
 #undef vfscanf
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/c_global/cstdlib gcc-4.9.3/libstdc++-v3/include/c_global/cstdlib
--- gcc-4.9.3.orig/libstdc++-v3/include/c_global/cstdlib	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/include/c_global/cstdlib	2015-06-30 05:09:32.000000000 +0200
@@ -182,7 +182,7 @@
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
 
-#if _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
 
 #undef _Exit
 #undef llabs
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/c_global/cwchar gcc-4.9.3/libstdc++-v3/include/c_global/cwchar
--- gcc-4.9.3.orig/libstdc++-v3/include/c_global/cwchar	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/include/c_global/cwchar	2015-06-30 05:09:32.000000000 +0200
@@ -232,7 +232,7 @@
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
 
-#if _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
 
 #undef wcstold
 #undef wcstoll
@@ -289,7 +289,7 @@
   using std::vwscanf;
 #endif
 
-#if _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
   using std::wcstold;
   using std::wcstoll;
   using std::wcstoull;
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/c_std/cstdio gcc-4.9.3/libstdc++-v3/include/c_std/cstdio
--- gcc-4.9.3.orig/libstdc++-v3/include/c_std/cstdio	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/include/c_std/cstdio	2015-06-30 05:09:32.000000000 +0200
@@ -144,7 +144,7 @@
   using ::vsprintf;
 } // namespace std
 
-#if _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
 
 #undef snprintf
 #undef vfscanf
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/c_std/cstdlib gcc-4.9.3/libstdc++-v3/include/c_std/cstdlib
--- gcc-4.9.3.orig/libstdc++-v3/include/c_std/cstdlib	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/include/c_std/cstdlib	2015-06-30 05:09:32.000000000 +0200
@@ -180,7 +180,7 @@
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
 
-#if _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
 
 #undef _Exit
 #undef llabs
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/c_std/cwchar gcc-4.9.3/libstdc++-v3/include/c_std/cwchar
--- gcc-4.9.3.orig/libstdc++-v3/include/c_std/cwchar	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/include/c_std/cwchar	2015-06-30 05:09:32.000000000 +0200
@@ -228,7 +228,7 @@
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
 
-#if _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
 
 #undef wcstold
 #undef wcstoll
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/ext/vstring.h gcc-4.9.3/libstdc++-v3/include/ext/vstring.h
--- gcc-4.9.3.orig/libstdc++-v3/include/ext/vstring.h	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/include/ext/vstring.h	2015-06-30 05:09:32.000000000 +0200
@@ -2680,7 +2680,7 @@
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
 
-#if ((__cplusplus >= 201103L) && defined(_GLIBCXX_USE_C99))
+#if ((__cplusplus >= 201103L) && (defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)))
 
 #include <ext/string_conversions.h>
 
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/tr1/cstdio gcc-4.9.3/libstdc++-v3/include/tr1/cstdio
--- gcc-4.9.3.orig/libstdc++-v3/include/tr1/cstdio	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/include/tr1/cstdio	2015-06-30 05:09:32.000000000 +0200
@@ -33,7 +33,7 @@
 
 #include <cstdio>
 
-#if _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
 
 namespace std _GLIBCXX_VISIBILITY(default)
 {
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/tr1/cstdlib gcc-4.9.3/libstdc++-v3/include/tr1/cstdlib
--- gcc-4.9.3.orig/libstdc++-v3/include/tr1/cstdlib	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/include/tr1/cstdlib	2015-06-30 05:09:32.000000000 +0200
@@ -35,7 +35,7 @@
 
 #if _GLIBCXX_HOSTED
 
-#if _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
 
 namespace std _GLIBCXX_VISIBILITY(default)
 {
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/tr1/cwchar gcc-4.9.3/libstdc++-v3/include/tr1/cwchar
--- gcc-4.9.3.orig/libstdc++-v3/include/tr1/cwchar	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/include/tr1/cwchar	2015-06-30 05:09:32.000000000 +0200
@@ -52,7 +52,7 @@
   using std::vwscanf;
 #endif
 
-#if _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
   using std::wcstold;
   using std::wcstoll;
   using std::wcstoull;
diff -Nur gcc-4.9.3.orig/libstdc++-v3/include/tr1/stdlib.h gcc-4.9.3/libstdc++-v3/include/tr1/stdlib.h
--- gcc-4.9.3.orig/libstdc++-v3/include/tr1/stdlib.h	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/include/tr1/stdlib.h	2015-06-30 05:09:32.000000000 +0200
@@ -33,7 +33,7 @@
 
 #if _GLIBCXX_HOSTED
 
-#if _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
 
 using std::tr1::atoll;
 using std::tr1::strtoll;
diff -Nur gcc-4.9.3.orig/libstdc++-v3/src/c++11/debug.cc gcc-4.9.3/libstdc++-v3/src/c++11/debug.cc
--- gcc-4.9.3.orig/libstdc++-v3/src/c++11/debug.cc	2014-01-02 23:30:10.000000000 +0100
+++ gcc-4.9.3/libstdc++-v3/src/c++11/debug.cc	2015-06-30 05:09:32.000000000 +0200
@@ -788,7 +788,7 @@
 				     int __n __attribute__ ((__unused__)), 
 				     const char* __fmt, _Tp __s) const throw ()
     {
-#ifdef _GLIBCXX_USE_C99
+#if defined(_GLIBCXX_USE_C99) || defined(__UCLIBC__)
       std::snprintf(__buf, __n, __fmt, __s);
 #else
       std::sprintf(__buf, __fmt, __s);