是什么在C ++中_tmain（）和main（）的区别？ [英] What is the difference between _tmain() and main() in C++?

问题描述

如果我跑我的C ++应用程序下面的main（）方法万事OK：

If I run my C++ application with the following main() method everything is OK:

int main(int argc, char *argv[]) 
{
   cout << "There are " << argc << " arguments:" << endl;

   // Loop through each argument and print its number and value
   for (int i=0; i<argc; i++)
      cout << i << " " << argv[i] << endl;

   return 0;
}

我得到了我希望和我的参数打印出来。

I get what I expect and my arguments are printed out.

不过，如果我使用_tmain：

However, if I use _tmain:

int _tmain(int argc, char *argv[]) 
{
   cout << "There are " << argc << " arguments:" << endl;

   // Loop through each argument and print its number and value
   for (int i=0; i<argc; i++)
      cout << i << " " << argv[i] << endl;

   return 0;
}

它只是显示每个参数的第一个字符。

It just displays the first character of each argument.

是什么造成这种区别？

推荐答案

_tmain 中不存在C ++。 主一样。

_tmain does not exist in C++. main does.

_tmain 是一个Microsoft扩展。

_tmain is a Microsoft extension.

主，根据C ++标准，程序的入口点。
它有两个特征之一：

main is, according to the C++ standard, the program's entry point. It has one of these two signatures:

int main();
int main(int argc, char* argv[]);

微软增加了一个wmain，与此代替第二签名：

Microsoft has added a wmain which replaces the second signature with this:

int wmain(int argc, wchar_t* argv[]);

然后，以使其更容易统一code（UTF-16）和多字节字符集之间切换，他们已经定义的 _tmain ，如果UNI code被启用，被编译为 wmain ，否则为主。

And then, to make it easier to switch between Unicode (UTF-16) and their multibyte character set, they've defined _tmain which, if Unicode is enabled, is compiled as wmain, and otherwise as main.

至于你的问题的第二部分，拼图的第一部分是你的主要功能是错误的。 wmain 应采取 wchar_t的参数，而不是字符。由于编译器不强制这个对主的功能，你就会得到一个程序，其中 wchar_t的字符串数组是传递到主功能，其中除$ p $其中pts他们为字符字符串。

As for the second part of your question, the first part of the puzzle is that your main function is wrong. wmain should take a wchar_t argument, not char. Since the compiler doesn't enforce this for the main function, you get a program where an array of wchar_t strings are passed to the main function, which interprets them as char strings.

现在，在UTF-16，使用的字符集由Windows当启用统一code，所有的ASCII字符重新psented为字节对$ P $ \\ 0 后跟的ASCII值。

Now, in UTF-16, the character set used by Windows when Unicode is enabled, all the ASCII characters are represented as the pair of bytes \0 followed by the ASCII value.

此外，由于x86处理器是小尾数，这些字节的顺序进行交换，从而使ASCII值是第一位的，然后由一个空字节。

And since the x86 CPU is little-endian, the order of these bytes are swapped, so that the ASCII value comes first, then followed by a null byte.

和在字符的字符串，是如何串通常终止？是的，一个空字节。所以，你的程序发现一串字符串，每一个字节长。

And in a char string, how is the string usually terminated? Yep, by a null byte. So your program sees a bunch of strings, each one byte long.

在一般情况下，你有三个选择做Windows程序设计时：

In general, you have three options when doing Windows programming:

• 明确使用统一code（调用wmain，并为这需要焦炭相关的参数每个Windows API函数，调用该函数的 -W 版本。相反， CreateWindow的的，叫CreateWindowW）。而不是使用字符使用 wchar_t的等


• 明确禁用的Uni code。通话为主，并CreateWindowA，并使用字符的字符串。


• 允许两者。 （呼叫_tmain和CreateWindow的，它决心主要/ _tmain和CreateWindowA / CreateWindowW），并使用替代字符/ wchar_t的TCHAR。

• Explicitly use Unicode (call wmain, and for every Windows API function which takes char-related arguments, call the -W version of the function. Instead of CreateWindow, call CreateWindowW). And instead of using char use wchar_t, and so on
• Explicitly disable Unicode. Call main, and CreateWindowA, and use char for strings.
• Allow both. (call _tmain, and CreateWindow, which resolve to main/_tmain and CreateWindowA/CreateWindowW), and use TCHAR instead of char/wchar_t.

这同样适用于由WINDOWS.H定义的字符串类型：
LPCTSTR解析为LPCSTR或LPCWSTR，并用于包括char或wchar_t的每一个其他类型，-T-版本始终存在可以替代使用。

The same applies to the string types defined by windows.h: LPCTSTR resolves to either LPCSTR or LPCWSTR, and for every other type that includes char or wchar_t, a -T- version always exists which can be used instead.

请注意，所有的这是微软具体。 TCHAR不是一个标准的C ++类，它是在WINDOWS.H中定义的宏。 wmain和_tmain也被微软定义只。

Note that all of this is Microsoft specific. TCHAR is not a standard C++ type, it is a macro defined in windows.h. wmain and _tmain are also defined by Microsoft only.

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