问题描述
当我想在C ++中使用 size_t 时，应包含< stddef.h> 或< cstddef> ？我听到几个人说，< cstddef> 是一个坏主意，它应该被弃用。为什么呢？
我更喜欢 #include< stddef.h> 。
C头文件中的一些名称可以是宏，但是集合不同于C规则。在C中， EXIT_FAILURE ， isdigit（）， getc > ao是宏。你知道哪些是C ++中的宏？
其次，只有几个标准的C头文件需要< cfoo& code>头，Posix头不是。你知道哪些标头是标准的，哪些是由你的编译器提供的？
第三，当使用第三方C库的头文件时， #include< stddef.h> ，我不喜欢混合< stddef.h> 第四，新C ++标准的当前草案说，< cstddef>
。 ; cstdlib> 允许将符号转储到全局命名空间中（因为显然很多编译器现在已经这么做），所以使用 #include< cstdlib> 不保证全局命名空间将来不会被污染。所以我建议，当写可移植代码，你应该假设全局命名空间将受到影响（即使它不允许现在）。由于只有少数专家似乎知道这一点（参见本文评论中的讨论），最好使用< stddef.h> ，因为即使是开始C ++程序员理解它污染了全局命名空间。
When I want to use size_t in C++, should I include <stddef.h> or <cstddef>? I have heard several people saying that <cstddef> was a bad idea, and it should be deprecated. Why is that?
I prefer #include <stddef.h>.
Some of the names in the C headers are allowed to be macros, but the set differs from the C rules. In C, EXIT_FAILURE, isdigit(), getc() a.o. are macros. Do you know which ones are macros in C++?
Secondly, only a couple standard C headers are required to have the <cfoo> header, Posix headers are not. Do you know which headers are standard and which ones are provided by your compiler only?
Thirdly, when using headers from a third-party C library, you will end up with #include <stddef.h>, and I prefer not to mix <stddef.h> and <cstddef>.
Fourthly, the current draft for the new C++ standard says that <cstdlib> is allowed to dump the symbols into the global namespace (because apparently many compilers already do so nowadays), so using #include <cstdlib> is not a guarantee that the global namespace will be unpolluted in the future. So I would advice that when writing portable code, you should assume the global namespace will be affected (even though it is not allowed now). As only a few experts seem to know this (see the discussion in the comments here), it is better to use <stddef.h> as even a beginning C++ programmer will understand that it pollutes the global namespace.
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