c++ – How to use std::stoul and std::stoull in Android?-ThrowExceptions

Exception or error:

C++11 has two new string conversion functions into unsigned long and long long: std::stoul() and std::stoll().

The recent Android NDK r9 introduces Clang 3.3 compiler which is said to be C++11 feature complete. There are prototypes for these functions deep inside NDK, however I cannot use them.

What do I need to do to use them?

P.S. I already do LOCAL_CPPFLAGS += -std=c++11

How to solve:

The reason why you cannot use the functions is quite deep rooted, and unfortunately currently unsolvable.

Looking into the libs/armeabi-v7a/include/bits/c++config.h file in the gnu stdlibc++ folder, you’ll see this:

/* Define if C99 functions or macros from <wchar.h>, <math.h>, <complex.h>,
   <stdio.h>, and <stdlib.h> can be used or exposed. */
/* #undef _GLIBCXX_USE_C99 */

The above, in conjunction with the following snippet from bits/basic_string.h spells bad news:

#if (defined(__GXX_EXPERIMENTAL_CXX0X__) && defined(_GLIBCXX_USE_C99) \

/* The definitions of Numeric Conversions [string.conversions] */

Thus, these functions are unusable in the NDK.

Root Cause: The root cause seems to be that the C99 functionality usage has been disabled in the GNU stdlibc++ on the armeabi-v7a platform due to the fact the the Bionic libc does not support complex math (the standard C library on Android is Bionic).

Possible Fix (untested): Explore CrystaX’s Android NDK which seems to have extensions over the Vanilla Android NDK.

Note: __GXX_EXPERIMENTAL_CXX0X__ is defined by adding -std=gnu++11 to APP_CXXFLAGS or LOCAL_CXXFLAGS

Detailed Test log: Built using NDK version r8e

APP_STL := gnustl_static
APP_CXXFLAGS += -std=gnu++11


LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE    := cxx11
LOCAL_SRC_FILES := cxx11.cpp


#include <iostream>
#include <string>

int main(int argc, char* argv[]) {
#if defined(__GXX_EXPERIMENTAL_CXX0X__)
    std::cout<<"__GXX_EXPERIMENTAL_CXX0X__ defined."<<std::endl;
    std::cout<<"__GXX_EXPERIMENTAL_CXX0X__ not defined."<<std::endl;

#if defined(_GLIBCXX_USE_C99)
    std::cout<<"_GLIBCXX_USE_C99 defined."<<std::endl;
    std::cout<<"_GLIBCXX_USE_C99 not defined."<<std::endl;

    std::cout<<"_GLIBCXX_HAVE_BROKEN_VSWPRINTF defined."<<std::endl;
    std::cout<<"_GLIBCXX_HAVE_BROKEN_VSWPRINTF not defined."<<std::endl;

#if (defined(__GXX_EXPERIMENTAL_CXX0X__) && defined(_GLIBCXX_USE_C99) \
    std::string s="1";
    std::cout<<"No support for stoll/stoul."<<std::endl;

Output on Nexus 4 (Android 4.3):

u0_a51@mako:/ $ /data/local/tmp/cxx11
_GLIBCXX_USE_C99 not defined.
No support for stoll/stoul.



APP_STL := c++_static

to Application.mk fixed my issue of not being able to access std::stoi() (using gcc 4.8.4).

solution via Daniel Tavares, from this Google Groups post.

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