c++ - 当使用 _ENABLE_PER_THREAD_LOCALE 时，STL 对象使用 C 运行时库语言环境进行浮点转换？

Question

C 运行时语言环境由 setlocale 设置。标准 C++ 库 (STL) 语言环境由 std::locale 类设置，并且可以在单个 STL 对象(如 std::istringstream 等)上设置。

函数 _configthreadlocale(_ENABLE_PER_THREAD_LOCALE) 允许在每个线程的基础上设置 C 运行时语言环境。

不幸的是，启用了 _configthreadlocale(_ENABLE_PER_THREAD_LOCALE) 的线程中的 STL 对象似乎正在使用 C 运行时语言环境。或者至少使用 C 运行时语言环境的小数点。

在没有 _ENABLE_PER_THREAD_LOCALE 的线程中没有问题。

Paavo 在 2008 年提出了类似的问题，但没有答案:_configthreadlocale and localeconv

以下代码显示了问题:

//Enable per thread locale in current thread  
_configthreadlocale(_ENABLE_PER_THREAD_LOCALE)  

//Create istringstream object  
std::istringstream LibraryStream;  
//Create double object  
double Value = 0;  
//Create std::locale object with "C" locale ("." as decimal point)  
std::locale StreamLoc("C");  
//Set C Runtime locale to danish ("," as decimal point)  
setlocale(LC_ALL, "danish");  

//Set the "C" locale on the istringstream object  
LibraryStream.imbue(StreamLoc);  
//Get the locale of the istringstream object for test (returns "C" as expected)  
std::locale NewStreamLoc = LibraryStream.getloc();  

//Set floating point string with "C" locale decimal point in istringstream object  
LibraryStream.str("60.258351");  
//Convert the string to double  
LibraryStream >> Value;  

//Now the expected value of "Value" is 60.258351, but it is 60.000  
//when debugging the conversion, I can see that "," is used as decimal point  

有没有人遇到过这种情况？难道我做错了什么？有解决方案的建议吗？

提前致谢/TEB

Answer 1

由于 C++ 标准库最近才获得有关线程的知识，所以这种明显的二分法并不让我感到惊讶。对不同场景中发生的情况进行了详尽的讨论(特定于 Microsoft，但作为一般背景似乎很有帮助)here .

总结:

To change the locale using the C++ Runtime Library, use the locale Class. By calling the locale::global method, you change the locale in every thread that has not explicitly enabled per-thread locale. To change the locale in a single thread or portion of an application, simply create an instance of a locale object in that thread or portion of code.