現象?

cocos2d-x 2.2.6 項目的源碼中使用了?std::to_string()?方法，使用 NDK r9d 編譯的時候，報如下錯誤：

error: 'to_string' is not a member of 'std'

Application.mk 文件的部分內容如下：

APP_STL := gnustl_static NDK_TOOLCHAIN_VERSION := 4.8 APP_CPPFLAGS := -frtti -std=c++11 -fexceptions -Wno-error=format-security -Wno-literal-suffix -Wno-deprecated-declarations -fsigned-char -Os $(CPPFLAGS)

換用 NDK 10e ，錯誤依然。

快速解決?

想快速解決這個問題，可以自己寫一個?std::to_string()?替換標準庫中的。

首先寫一個?stdtostring.h?文件：

#ifndef STDTOSTRING_H #define STDTOSTRING_H #include <string> #include <sstream>using namespace std; namespace std {template < typename T > std::string to_string( const T& n ){std::ostringstream stm ;stm << n ;return stm.str() ;} } #endif

然后在需要使用?std::to_stirng()?方法的源文件中包含它：

#if CC_TARGET_PLATFORM == CC_PLATFORM_ANDROID #include "stdtostring.h" #endif

追根溯源?

Why gnustl_static?中介紹了采用?c++_static?和?clang?編譯器來實現std::to_string()?支持，于是我嘗試了下：

# APP_STL := gnustl_static # NDK_TOOLCHAIN_VERSION := 4.8 APP_STL := c++_static NDK_TOOLCHAIN_VERSION := clang

根據?C++ Library Support?的說明，?c++_static?對應的是 The LLVM libc++ runtime (static) ，因此應該采用 clang 的工具鏈進行編譯。

結果是：?std::to_string()?編譯正常，但出現下面的錯誤：

In file included from src/Utilities.cpp:1:0: android-ndk-r9d/sources/cxx-stl/llvm-libc++/libcxx/include/cmath:1498:46: error: expected unqualified-id before 'float' inline _LIBCPP_INLINE_VISIBILITY float remainder(float __x, float __y) _NOEXCEPT {return remainderf(__x, __y);}^ android-ndk-r9d/sources/cxx-stl/llvm-libc++/libcxx/include/cmath:1498:46: error: expected ')' before 'float' android-ndk-r9d/sources/cxx-stl/llvm-libc++/libcxx/include/cmath:1499:46: error: expected unqualified-id before 'long' inline _LIBCPP_INLINE_VISIBILITY long double remainder(long double __x, long double __y) _NOEXCEPT {return remainderl(__x, __y);}^ android-ndk-r9d/sources/cxx-stl/llvm-libc++/libcxx/include/cmath:1499:46: error: expected ')' before 'long' android-ndk-r9d/sources/cxx-stl/llvm-libc++/libcxx/include/cmath:1509:1: error: expected ')' before '__x' remainder(_A1 __x, _A2 __y) _NOEXCEPT ^ android-ndk-r9d/sources/cxx-stl/llvm-libc++/libcxx/include/cmath:1559:46: error: expected unqualified-id before 'float' inline _LIBCPP_INLINE_VISIBILITY float round(float __x) _NOEXCEPT {return roundf(__x);}^ android-ndk-r9d/sources/cxx-stl/llvm-libc++/libcxx/include/cmath:1559:46: error: expected ')' before 'float' android-ndk-r9d/sources/cxx-stl/llvm-libc++/libcxx/include/cmath:1560:46: error: expected unqualified-id before 'long' inline _LIBCPP_INLINE_VISIBILITY long double round(long double __x) _NOEXCEPT {return roundl(__x);}^ android-ndk-r9d/sources/cxx-stl/llvm-libc++/libcxx/include/cmath:1560:46: error: expected ')' before 'long' android-ndk-r9d/sources/cxx-stl/llvm-libc++/libcxx/include/cmath:1565:1: error: expected ')' before '__x' round(_A1 __x) _NOEXCEPT {return round((double)__x);}

minggo?在?Cocos can’t compile Android with APP_STL := c++_static?中提到：

A prebuilt version can only support one type of c++ lib. Did you mean we should provide two kinds of prebuilt libcocos2d that using two different c++ libs?

I don’t know if cocos2d can compile with c++_static or not. I don’t remember if there is a good reason to choose one instead of other one. But cocos2d-x uses gnustl_static from very early version, so we know it works well. You can replace it with c++_static if you like, but it is not fully tested.

因此我懷疑在 cocos2d-x 的舊版本中，?c++_static?是沒有經過完整測試的。

也有人說?在新版本（>3.7）中，?gnustl_static?會導致 lambda 和std::to_string?不能使用，已經切換到使用?c++_static?和 clange 組合。

I never made it to work with gnustl_static and gcc with all the c++11 features. I was getting crashes in simple lambdas, as mentioned std::to_string was missing and much more, so i’ve switched to c++_static and clang long time ago.

本文轉自：http://www.tuicool.com/articles/RBBjMz

轉載于:https://www.cnblogs.com/Anzhongliu/p/6091789.html

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