的swprintf（）窄弦 [英] swprintf() with narrow strings

问题描述

code以下行给出了垃圾与Visual Studio 2010：

The following line of code gives garbage with Visual Studio 2010:

swprintf(buf, L"Value is %s", "abcd");

然而，同样的code正常工作在Linux上。

However, the same code works fine on Linux.

通过试验，我可以使它由Visual Studio下，使用％S代替％S的工作。

By trial, I could make it work by using %S instead of %s under Visual Studio.

swprintf(buf, L"Value is %S", "abcd");

我想知道，如果这是在Visual Studio 2010中的错误还是我失去了一些东西。问候。

I am wondering if this is a bug in Visual Studio 2010 or am I missing something. Regards.

推荐答案

这是一个错误，虽然该行为是由设计。最初的Visual C ++实现宽字符串的printf和scanf函数$ P $的pdated其标准化C，在某些情况下的行为，从被C标准库规范需要什么样的偏离。

This is a "bug," though the behavior is by design. The initial Visual C++ implementation of the wide string printf and scanf functions predated their standardization in C, and in some cases the behavior deviates from what is required by the C Standard Library specification.

在C标准库规范中，％S 或％C 格式说明必须始终与配对字符数组或元素，而→长度修改时，必须使用一个 wchar_t的提供数组或元素。

In the C Standard Library specification, a %s or %c format specifier must always be paired with a char array or element, and the l length modifier must be used when a wchar_t array or element is provided.

在Visual C ++实现的这些功能​​（文档）在％S 和％C 格式说明期望的自然宽度的相应参数。对于窄字符串的printf和scanf函数，一个字符指针或元素是必需的和广泛的字符串函数 wchar_t的指针或元件是必需的。要通过其他宽度的字符串，可以使用％S 和％C 格式说明。另外， ^ h 和→可用于长度修改明确指定该字符串参数是一个窄或宽字符串

In the Visual C++ implementation of these functions (documentation), the %s and %c format specifiers expect a corresponding argument of the "natural" width. For the narrow string printf and scanf functions, a char pointer or element is required and for the wide string functions a wchar_t pointer or element is required. To pass a string of the "other" width, the %S and %C format specifiers may be used. Alternatively, the h and l length modifiers may be used to explicitly specify that the string argument is a narrow or wide string.

在其他的优势，Visual C ++实现的这些功能​​使我们能够轻松地迁移旧code通过的在 _TCHAR 在＆LT映射> 。不幸的是，什么是标准化的东西已经在Visual C ++实现实施不同的（我不熟悉这里的历史;它可能是什么标准匹配的另一种实现方式。）

Among other advantages, the Visual C++ implementation of these functions made it possible to easily migrate old code to use Unicode strings via the _TCHAR mappings in <tchar.h>. It is unfortunate that what was standardized was different from what had already been implemented in the Visual C++ implementation (I am not familiar with the history here; it may be that what was standardized matched another implementation.).

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