to_string() not declared in gnustl_static

This code will give error message "to_string was not declared in this scope"

#include <jni.h>
#inlcude <string>
#include <android/log.h>

JNIEXPORT jboolean JNICALL Java_com_package_activity_method
(JNIEnv *env, jobject classObject,jdouble number) {
  String string= to_string(number);
   __android_log_print(ANDROID_LOG_DEBUG, "JNI","The number is: %s,string);
  return;
}

if trace the header file I can find these in string.h -> basic_string.h

inline string
to_string(double __val)
{
  const int __n = 
   __gnu_cxx::__numeric_traits<double>::__max_exponent10 + 20;
  return __gnu_cxx::__to_xstring<string>(&std::vsnprintf, __n,
                   "%f", __val);
}

So it was declared after all...

I can fix the problem by write my own version of to_string

String to_string(double number){
    std::stringstream ss;
    ss << number;
    return ss.str();  }

or change -DANDROID_STL to c++_static

but what I am trying understand it which part of the code obscure the to_string method in gnustl from being seen.