C++ __STDC_LIMIT_MACROS 和 __STDC_CONSTANT_MACROS 是什么意思？
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What do __STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS mean?
提问by Matthew Willis
I see this in the standard C++ libraries for my system, as well as some of the headers in a library I'm using.
我在系统的标准 C++ 库以及我正在使用的库中的一些头文件中看到了这一点。
What are the semantics of these two definitions? Is there a good reference for #defines like this other than the source itself?
这两个定义的语义是什么？除了源本身之外，是否有像这样的#defines 的很好的参考？
回答by Dingo
__STDC_LIMIT_MACROSand __STDC_CONSTANT_MACROSare a workaround to allow C++ programs to use stdint.hmacros specified in the C99 standard that aren't in the C++ standard. The macros, such as UINT8_MAX, INT64_MIN, and INT32_C()may be defined already in C++ applications in other ways. To allow the user to decide if they want the macros defined as C99 does, many implementations require that __STDC_LIMIT_MACROSand __STDC_CONSTANT_MACROSbe defined before stdint.his included.
__STDC_LIMIT_MACROS并且__STDC_CONSTANT_MACROS是一种允许 C++ 程序使用stdint.hC99 标准中指定但不在 C++ 标准中的宏的变通方法。宏，例如UINT8_MAX, INT64_MIN, 和INT32_C()可能已经以其他方式在 C++ 应用程序中定义。为了让用户决定他们是否想要像 C99 那样定义的宏，许多实现都要求__STDC_LIMIT_MACROS并__STDC_CONSTANT_MACROS在stdint.h包含之前定义。
This isn't part of the C++ standard, but it has been adopted by more than one implementation.
这不是 C++ 标准的一部分，但它已被不止一个实现采用。
回答by malat
The above issue has vanished. C99 is an old standard, so this has been explicitly overruled in the C++11 standard, and as a consequence C11 has removed this rule.
上述问题已不复存在。C99 是一个旧标准，因此在 C++11 标准中已明确否决了这一点，因此 C11 已删除此规则。
More details there:
更多详情：
回答by laalto
In stdint.hunder C++, they control whether to define macros like INT32_MAXor INT32_C(v). See your platform's stdint.hfor additional information.
在stdint.hC++ 下，它们控制是否定义宏，如INT32_MAX或INT32_C(v)。有关stdint.h其他信息，请参阅您的平台。
回答by laalto
The macros are not part of the C++ standard and are probably used for internal purposes in your C++ implementation. If you want to know more about them, you should ask a question with atag that indicates what that implementation is.
宏不是 C++ 标准的一部分，可能在 C++ 实现中用于内部目的。如果您想了解更多关于它们的信息，您应该问一个带有 atag 的问题，表明该实现是什么。
