无法将'const char *'转换为'LPCWSTR {aka const wchar_t *}' [英] cannot convert 'const char*' to 'LPCWSTR {aka const wchar_t*}'

问题描述

我的C ++代码出现错误，我无法理解。剥离的代码位在这里：

I'm getting an error in my C++ code that I can't quite make sense of. The stripped down code bits are here:

RS232Handle=OpenRS232("COM1", 9600);

HANDLE OpenRS232(const char* ComName, DWORD BaudRate)
{
    ComHandle=CreateFile(ComName, GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
}

我收到以下错误：

error: cannot convert 'const char*' to 'LPCWSTR {aka const wchar_t*}' for argument '1' to 'void* CreateFileW(LPCWSTR, DWORD, DWORD, LPSECURITY_ATTRIBUTES, DWORD, DWORD, HANDLE)'
     ComHandle=CreateFile(ComName, GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);

该代码取自VS代码，我现在使用的是Qt Creator。

The code was taken from VS code and I am now using Qt creator.

如何解决此问题？谢谢！

How can I fix this issue? Thanks!

推荐答案

Windows CreateFile 函数实际上是一个扩展为以下其中之一的宏：

The Windows CreateFile function is actually a macro that expands to one of:

• CreateFileA ，其文件类型为 const char *


• CreateFileW ，该文件路径的类型为 const wchar_t * 。

• CreateFileA, which takes a file path of type const char*
• CreateFileW, which takes a file path of type const wchar_t*.

（对于Windows API中大多数采用字符串的功能，都是如此。）

(The same is true for most of the functions in the Windows API that take a string.)

您要声明参数 const char * ComName ，但显然使用已定义的 UNICODE 进行编译，因此它正在调用该函数的 W 版本。从 const wchar_t * 到 const char * 不会自动转换，因此会出错。

You're declaring the parameter const char* ComName, but apparently compiling with UNICODE defined, so it's calling the W version of the function. There's no automatic conversion from const wchar_t* to const char*, hence the error.

您的选项是：

1. 将函数参数更改为UTF-16（ const wchar_t * ）字符串。


2. 保留 char * 参数，但将函数显式转换转换为具有 MultiByteToWideChar 。


3. 显式调用 CreateFileA 而不是 CreateFile 。


4. 不使用 UNICODE 编译程序，以便宏扩展为 A 版本。


5. 绑架一位著名的Microsoft开发人员，并强迫他阅读 UTF-8 Everywhere ，直到他同意让Windows完全支持UTF-8作为 ANSI代码页为止。我们将Windows开发人员从众多字符中解放出来。

1. Change the function parameter to a UTF-16 (const wchar_t*) string.
2. Keep the char* parameter, but have your function explicitly convert it to a UTF-16 string with a function like MultiByteToWideChar.
3. Explicitly call CreateFileA instead of CreateFile.
4. Compile your program without UNICODE, so that the macros expand to the A versions by default.
5. Kidnap a prominent Microsoft developer and force him to read UTF-8 Everywhere until he agrees to have Windows fully support UTF-8 as an "ANSI" code page, thus freeing Windows developers everywhere from this wide-character stuff.

编辑：，我不知道涉及绑架，但Windows 10 1903最终添加了支持将UTF-8作为ANSI代码页。

I don't know if a kidnapping was involved, but Windows 10 1903 finally added support for UTF-8 as an ANSI code page.

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