如何使用std :: stoul和std :: stoull在Android中？ [英] How to use std::stoul and std::stoull in Android?

问题描述

C ++ 11有两个新的字符串转换函数为无符号长和很长很长：的std :: stoul（）和的std ::斯托尔（）。

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

近期的Andr​​oid NDK R9介绍锵3.3编译器被认为是C ++ 11功能齐全。有这些函数的原型内心深处NDK，不过，我可以不使用它们。

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.

什么我需要做的，使用他们？

What do I need to do to use them?

PS 我已经做 LOCAL_CPPFLAGS + = -std = C ++ 11

推荐答案

为什么你不能使用的功能的原因很根深蒂固的，可惜目前无法解决的。

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

展望库/ armeabi-V7A /包括/位/ C ++的config.h 在GNU stdlibc ++文件夹中的文件，你会看到这一点：

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 */
...

以上，与下面的代码片段一起从位/ basic_string.h 法术坏消息：

...
#if (defined(__GXX_EXPERIMENTAL_CXX0X__) && defined(_GLIBCXX_USE_C99) \
     && !defined(_GLIBCXX_HAVE_BROKEN_VSWPRINTF))

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

因此​​，这些功能都无法使用的NDK。

Thus, these functions are unusable in the NDK.

根本原因：的根本原因似乎是对C99功能的使用已经在armeabi-V7A平台上的GNU stdlibc ++被禁用由于这样的事实的仿生libc中不支持复杂的数学（在Android标准C库是仿生）。

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).

可能修复（未测试）：探索 CrystaX的Andr​​oid NDK 似乎有扩展在香草的Andr​​oid NDK。

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

注意： __ GXX_EXPERIMENTAL_CXX0X __ 通过添加定义 -std = GNU + 11 以 APP_CXXFLAGS 或 LOCAL_CXXFLAGS

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

详细的测试日志：内置使用NDK版本R8E
JNI / Application.mk 的：

Detailed Test log: Built using NDK version r8e
jni/Application.mk:

APP_STL := gnustl_static
APP_CXXFLAGS += -std=gnu++11
NDK_TOOLCHAIN_VERSION := 4.7

JNI / Android.mk 的

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

JNI / cxx11.cpp 的：

#include <iostream>
#include <string>

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

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

#if defined(_GLIBCXX_HAVE_BROKEN_VSWPRINTF)
    std::cout<<"_GLIBCXX_HAVE_BROKEN_VSWPRINTF defined."<<std::endl;
#else
    std::cout<<"_GLIBCXX_HAVE_BROKEN_VSWPRINTF not defined."<<std::endl;
#endif

#if (defined(__GXX_EXPERIMENTAL_CXX0X__) && defined(_GLIBCXX_USE_C99) \
     && !defined(_GLIBCXX_HAVE_BROKEN_VSWPRINTF))
    std::string s="1";
    std::cout<<"ll:"<<std::stoll(s)<<std::endl<<"ul:"<<std::stoul(s)<<std::endl;
#else
    std::cout<<"No support for stoll/stoul."<<std::endl;
#endif
    return(0);
}

输出在Nexus 4（安卓4.3）：

Output on Nexus 4 (Android 4.3):

u0_a51@mako:/ $ /data/local/tmp/cxx11
__GXX_EXPERIMENTAL_CXX0X__ defined.
_GLIBCXX_USE_C99 not defined.
_GLIBCXX_HAVE_BROKEN_VSWPRINTF not defined.
No support for stoll/stoul.

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