C++ 语言预定义宏

红太狼 2022-09-03 01:22 225阅读 0赞

#  C++ 语言预定义宏 #

## 1. 标准预定义标识符 - Standard predefined identifier ##

ISO C99 和 ISO C++11 指定的预定义标识符：  
`__func__` The unqualified and unadorned name of the enclosing function as a function-local `static const` array of `char`.  
封闭函数 (用作 `char` 的函数局部 `static const` 数组) 的未限定、未修饰名称

## 2. 标准预定义宏 - Standard predefined macros ##

ISO C99、C11、C17 和 ISO C++17 标准指定的预定义宏：

`__cplusplus` Defined as an integer literal value when the translation unit is compiled as C++. Otherwise, undefined.  
当翻译单元编译为 C++ 时，定义为整数文本值。其他情况下则不定义。

`__DATE__` The compilation date of the current source file. The date is a constant length string literal of the form `Mmm dd yyyy`. The month name Mmm is the same as the abbreviated month name generated by the C Runtime Library (CRT) asctime function. The first character of date `dd` is a space if the value is less than 10. This macro is always defined.  
当前源文件的编译日期。日期是 `Mmm dd yyyy` 格式的恒定长度字符串文本。月份名 Mmm 与 C 运行时库 (CRT) `asctime` 函数生成的缩写月份名相同。如果值小于 10，则日期 `dd` 的第一个字符为空格。任何情况下都会定义此宏。

`__FILE__` The name of the current source file. `__FILE__` expands to a character string literal. To ensure that the full path to the file is displayed, use /FC (Full Path of Source Code File in Diagnostics). This macro is always defined.  
当前源文件的名称。`__FILE__` 展开为字符型字符串文本。要确保显示文件的完整路径，请使用 `/FC` (诊断中源代码文件的完整路径)。任何情况下都会定义此宏。

`__LINE__` Defined as the integer line number in the current source file. The value of the `__LINE__` macro can be changed by using a \#line directive. This macro is always defined.  
定义为当前源文件中的整数行号。可使用 `#line` 指令来更改 `__LINE__` 宏的值。任何情况下都会定义此宏。

`__STDC__` Defined as 1 only when compiled as C and if the `/Za` compiler option is specified. Otherwise, undefined.  
仅在编译为 C，并且指定了编译器选项时，定义为 `/Za`。其他情况下则不定义。

`__STDC_HOSTED__` Defined as 1 if the implementation is a hosted implementation, one that supports the entire required standard library. Otherwise, defined as 0.  
如果实现是托管实现并且支持整个必需的标准库，则定义为 1。其他情况下则定义为 0。

`__STDC_NO_ATOMICS__` Defined as 1 if the implementation doesn’t support optional standard atomics. The MSVC implementation defines it as 1 when compiled as C and one of the `/std` C11 or C17 options is specified.  
如果实现不支持可选的标准原子，则定义为 1。当编译为 C 且指定 `/std` C11 或 C17 选项之一时，MSVC 实现会将其定义为 1。

`__STDC_NO_COMPLEX__` Defined as 1 if the implementation doesn’t support optional standard complex numbers. The MSVC implementation defines it as 1 when compiled as C and one of the `/std` C11 or C17 options is specified.  
如果实现不支持可选的标准复数，则定义为 1。当编译为 C 且指定 `/std` C11 或 C17 选项之一时，MSVC 实现会将其定义为 1。

`__STDC_NO_THREADS__` Defined as 1 if the implementation doesn’t support optional standard threads. The MSVC implementation defines it as 1 when compiled as C and one of the `/std` C11 or C17 options is specified.  
如果实现不支持可选的标准线程，则定义为 1。当编译为 C 且指定 `/std` C11 或 C17 选项之一时，MSVC 实现会将其定义为 1。

`__STDC_NO_VLA__` Defined as 1 if the implementation doesn’t support standard variable length arrays. The MSVC implementation defines it as 1 when compiled as C and one of the /std C11 or C17 options is specified.  
如果实现不支持可选的可变长度数组，则定义为 1。当编译为 C 且指定 `/std` C11 或 C17 选项之一时，MSVC 实现会将其定义为 1。

`__STDC_VERSION__` Defined when compiled as C and one of the `/std` C11 or C17 options is specified. It expands to 201112L for `/std:c11`, and 201710L for `/std:c17`.  
当编译为 C 且指定 `/std` C11 或 C17 选项之一时定义。对于 `/std:c11`，它扩展到 201112L；对于 `/std:c17`，则扩展到 201710L。

`__STDCPP_THREADS__` Defined as 1 if and only if a program can have more than one thread of execution, and compiled as C++. Otherwise, undefined.  
当且仅当程序可以有多个执行线程并编译为 C++ 时，定义为 1。 其他情况下则不定义。

`__TIME__` The time of translation of the preprocessed translation unit. The time is a character string literal of the form `hh:mm:ss`, the same as the time returned by the CRT asctime function. This macro is always defined.  
预处理翻译单元的翻译时间。时间是 `hh:mm:ss` 格式的字符型字符串文本，与 CRT `asctime` 函数返回的时间相同。任何情况下都会定义此宏。

## 3. C++ 语言中的预定义宏 ##

__LINE__：当前行号。
    __FILE__：当前文件名。
    __DATE__：形式为 month day year 的字符串，表示把源文件转换为目标代码的日期。
    __TIME__：形式为 hour:minute:second 的字符串，表示程序被编译的时间。

//============================================================================
    // Name        : Yongqiang Cheng
    // Author      : Yongqiang Cheng
    // Version     : Version 1.0.0
    // Copyright   : Copyright (c) 2020 Yongqiang Cheng
    // Description : Hello World in C++, Ansi-style
    //============================================================================
    
    #include <iostream>
    
    int main()
    {
    	std::cout << "__func__ : " << __func__ << std::endl;
    	std::cout << "__LINE__ : " << __LINE__ << std::endl;
    	std::cout << "__FILE__ : " << __FILE__ << std::endl;
    	std::cout << "__DATE__ : " << __DATE__ << std::endl;
    	std::cout << "__TIME__ : " << __TIME__ << std::endl << std::endl;
    
    	return 0;
    }

__func__ : main
    __LINE__ : 14
    __FILE__ : d:\visual_studio_workspace\hash_table\hash_table\yongqiang.cpp
    __DATE__ : Aug  4 2021
    __TIME__ : 23:35:44
    
    请按任意键继续. . .

## References ##

[https://www.runoob.com/cplusplus/cpp-tutorial.html][https_www.runoob.com_cplusplus_cpp-tutorial.html]  
[https://docs.microsoft.com/en-us/cpp/cpp/][https_docs.microsoft.com_en-us_cpp_cpp]  
[https://docs.microsoft.com/zh-cn/cpp/cpp/][https_docs.microsoft.com_zh-cn_cpp_cpp]

[https_www.runoob.com_cplusplus_cpp-tutorial.html]: https://www.runoob.com/cplusplus/cpp-tutorial.html
[https_docs.microsoft.com_en-us_cpp_cpp]: https://docs.microsoft.com/en-us/cpp/cpp/
[https_docs.microsoft.com_zh-cn_cpp_cpp]: https://docs.microsoft.com/zh-cn/cpp/cpp/