使用wscanf在C中处理宽字符时出现问题。

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英文:

Problem using wscanf in c for wide characters

问题

当我尝试输入3个字符时,其中一个是 å。以下是代码部分:

#ifdef _MSC_VER
#include <io.h>     // _setmode
#include <fcntl.h>  // _O_U16TEXT
#endif

#include <stdio.h>
#include <locale.h>
#include <wchar.h>
#define SIZE 4

void set_locale_mode() {
   #ifdef _MSC_VER
   // Unicode UTF-16, little endian byte order (BMP of ISO 10646)
   const char *CP_UTF_16LE = ".1200";

   setlocale(LC_ALL, CP_UTF_16LE);
   _setmode(_fileno(stdout), _O_U16TEXT);
   #else
      setlocale(LC_ALL, "");
   #endif
}

int main(void) {
   set_locale_mode(); 
   wchar_t myString[SIZE];
   wchar_t testChar=0x00E5;

   wprintf(L"Your test character is %lc\n", testChar);
   printf("Now, enter 3 characters: ");
   wscanf(L"%ls", myString);
   wprintf(L"Your input is %ls\n", myString);

   return 0;
}

然而,当我输入例如 blå 时,我得到这个输出:

Your test character is å
Now, enter 3 characters: blå
Your input is bl�
为什么在使用 wscanf 后 &#229; 没有正确打印出来?

我在 Windows 上。

为什么在使用 wscanf 后,å 没有正确打印出来?

英文:

I am trying to enter 3 characters, one of which is å. Here is the code:

#ifdef _MSC_VER
#include &lt;io.h&gt;     // _setmode
#include &lt;fcntl.h&gt;  // _O_U16TEXT
#endif

#include &lt;stdio.h&gt;
#include &lt;locale.h&gt;
#include &lt;wchar.h&gt;
#define SIZE 4

void set_locale_mode() {
   #ifdef _MSC_VER
   // Unicode UTF-16, little endian byte order (BMP of ISO 10646)
   const char *CP_UTF_16LE = &quot;.1200&quot;;

   setlocale(LC_ALL, CP_UTF_16LE);
   _setmode(_fileno(stdout), _O_U16TEXT);
   #else
      setlocale(LC_ALL, &quot;&quot;);
   #endif
}


int main(void) {

   set_locale_mode(); 
   wchar_t myString[SIZE];
   wchar_t testChar=0x00E5;

   wprintf(L&quot;Your test character is %lc\n&quot;, testChar);
   printf(&quot;Now, enter 3 characters: &quot;);
   wscanf(L&quot;%ls&quot;, myString);
   wprintf(L&quot;Your input is %ls\n&quot;, myString);

   return 0;
}

However when I enter for example blå I get this output:

You test character is &#229;
Now, enter 3 characters: bl&#229; 
Your input is bl┼

Why does not å get printed correctly after I use wscanf?

I am on windows.

答案1

得分: 3

由于您希望输入也使用 _O_U16TEXT,请将其添加到 set_locale_mode 函数中。

我还建议不要混合使用“宽”输出和窄输出,例如 wprintfprintf

#if defined(_MSC_VER) || defined(__MINGW32__) || defined(__MINGW64__)
// 或许已经有一个宏来定义这个,但我不知道:
#define ON_WINDOWS
#endif

#ifdef ON_WINDOWS
#define _CRT_SECURE_NO_WARNINGS
#include <io.h>     // _setmode
#include <fcntl.h>  // _O_U16TEXT

// 以防万一mingw没有定义它:
#ifndef _O_U16TEXT
#define _O_U16TEXT (0x20000)
#endif
#endif

#include <stdio.h>
#include <locale.h>
#include <wchar.h>
#define SIZE 4

void set_locale_mode() {
#ifdef ON_WINDOWS
    // Unicode UTF-16,小端字节序(ISO 10646的BMP)
    const char* CP_UTF_16LE = ".1200";

    setlocale(LC_ALL, CP_UTF_16LE);
    _setmode(_fileno(stdin), _O_U16TEXT);                // <- 添加了这一行
    _setmode(_fileno(stdout), _O_U16TEXT);
#else
    setlocale(LC_ALL, "");
#endif
}

int main(void) {
    set_locale_mode();

    wchar_t myString[SIZE];
    wchar_t testChar = u'\u00E5'; // 显示意图比0x00E5更清晰

    wprintf(L"您的测试字符是 %lc\n", testChar);
    wprintf(L"现在,请输入3个字符:");              // <- 在这里使用wprintf
    wscanf(L"%3ls", myString); // <- 由于SIZE为4,限制为3个字符
    wprintf(L"您的输入是 %ls\n", myString);
}
英文:

Since you want input to be using _O_U16TEXT too, add that to the set_locale_mode function.

I also suggest not mixing "wide" output with narrow, like wprintf and printf.

#if defined(_MSC_VER) || defined(__MINGW32__) || defined(__MINGW64__)
// perhaps there is already a macro for this, but I don&#39;t know of one:
#define ON_WINDOWS
#endif

#ifdef ON_WINDOWS
#define _CRT_SECURE_NO_WARNINGS
#include &lt;io.h&gt;     // _setmode
#include &lt;fcntl.h&gt;  // _O_U16TEXT

// just in case mingw doesn&#39;t define it after all:
#ifndef _O_U16TEXT
#define _O_U16TEXT (0x20000)
#endif
#endif

#include &lt;stdio.h&gt;
#include &lt;locale.h&gt;
#include &lt;wchar.h&gt;
#define SIZE 4

void set_locale_mode() {
#ifdef ON_WINDOWS
    // Unicode UTF-16, little endian byte order (BMP of ISO 10646)
    const char* CP_UTF_16LE = &quot;.1200&quot;;

    setlocale(LC_ALL, CP_UTF_16LE);
    _setmode(_fileno(stdin), _O_U16TEXT);                // &lt;- Added
    _setmode(_fileno(stdout), _O_U16TEXT);
#else
    setlocale(LC_ALL, &quot;&quot;);
#endif
}


int main(void) {
    set_locale_mode();

    wchar_t myString[SIZE];
    wchar_t testChar = u&#39;\u00E5&#39;; // shows intent clearer than 0x00E5

    wprintf(L&quot;Your test character is %lc\n&quot;, testChar);
    wprintf(L&quot;Now, enter 3 characters: &quot;);              // &lt;- Use wprintf here
    wscanf(L&quot;%3ls&quot;, myString); // &lt;- limit to 3 since SIZE is 4
    wprintf(L&quot;Your input is %ls\n&quot;, myString);
}

答案2

得分: 2

代码遇到了未定义行为(UB),因为它尝试使用不同的_方向_进行写入。

每个流都有一个_方向_。在将流关联到外部文件之后,但在对其执行任何操作之前,该流是未定向的。一旦对未定向流应用了宽字符输入/输出函数,该流就会成为宽定向流。同样,一旦对未定向流应用了字节输入/输出函数,该流就会成为字节定向流。只有对freopen函数或fwide函数的调用才能否则更改流的方向。(对freopen的成功调用会删除任何方向。)
不得将字节输入/输出函数应用于宽定向流,也不得将宽字符输入/输出函数应用于字节定向流。...
C23dr § 7.23.2 4-5

使用与@Ted Lyngmo建议的相同方向,或者移除方向。

wprintf(L"Your test character is %lc\n", testChar);
freopen(NULL, "w", stdout);
printf("Now, enter 3 characters: ");
freopen(NULL, "w", stdout);
wprintf(L"...");
英文:

Code runs into undefined behavior (UB) as it attempts to write using a different orientation.

> Each stream has an orientation. After a stream is associated with an external file, but before any operations are performed on it, the stream is unoriented. Once a wide character input/output function has been applied to an unoriented stream, the stream becomes a wide-oriented stream. Similarly, once a byte input/output function has been applied to an unoriented stream, the stream becomes a byte-oriented stream. Only a call to the freopen function or the fwide function can otherwise alter the orientation of a stream. (A successful call to freopen removes any orientation.)
> Byte input/output functions shall not be applied to a wide-oriented stream and wide character input/output functions shall not be applied to a byte-oriented stream. ...
> C23dr § 7.23.2 4-5

Use the same orientation as well suggested by @Ted Lyngmo or remove the orientation.

wprintf(L&quot;Your test character is %lc\n&quot;, testChar);
freopen(NULL, &quot;w&quot;, stdout);
printf(&quot;Now, enter 3 characters: &quot;);
freopen(NULL, &quot;w&quot;, stdout);
wprintf(L&quot;...&quot;);

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  • 本文由 发表于 2023年6月29日 00:29:17
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