blocks|key|2606327|text|C的size_t和C%2B%2B的std::size_t都是一样的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2606328|在C中，它是在<stddef.h>和C%2B%2B中定义的，它是在<cstddef>中定义的，其内容与C+header相同(参见下面的引号)。它被定义为sizeof运算符的结果的无符号整数类型。|BOLD|2606329|C标准在§17.7/2中说，|2606330|2606331|+size_t，是sizeof运算符的结果的无符号整数类型|blockquote|2606332|2606333|2606334|而C%2B%2B标准在§18.1/3中说(关于cstddef报头)，|2606335|2606336|其内容与标准C库头文件相同，但有以下变化。|2606337|2606338|2606339|所以，两者是一样的；唯一的区别是C%2B%2B在std+命名空间中定义了。|2606340|还请注意，上面的代码行还显示了“具有以下更改”，这并不是指size_t。更确切地说，它指的是C%2B%2B对语言(不是C语言)所做的新添加(主要是)，这些新添加也定义在同一个头中。|2606341|2606342|维基百科有关于size_t的范围和存储大小的非常好的信息：|2606343|2606344|+范围和size_t的存储大小|2606345|2606346|例如，当从32位体系结构迁移到64位体系结构时，size_t的实际整数类型是a+size_t+假设size_t与无符号整数相同，这可能导致编程错误，3。|2606347|根据1999ISO+C标准(C99)，size_t是至少16位的无符号整数类型。|2606348|2606349|剩下的你可以在维基百科的this+page上读到。|2606350|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Size_t^0|2|6|D|B|0|7|A|T|9|20|6|0|0|0|9|6|0|0|0|J|7|0|0|0|0|0|K|3|O|9|K|3|0|T|6|0|0|0|0|1|9|0|0|12|1|0|0|0|C|9|0|0^^$0|@$1|2|3|4|5|6|7|1N|8|@$9|1O|A|1P|B|C]|$9|1Q|A|1R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1S|8|@$9|1T|A|1U|B|C]|$9|1V|A|1W|B|C]|$9|1X|A|1Y|B|H]]|D|@]|E|$]]|$1|I|3|J|5|6|7|1Z|8|@]|D|@]|E|$]]|$1|K|3|-4|5|6|7|20|8|@]|D|@]|E|$]]|$1|L|3|M|5|N|7|21|8|@$9|22|A|23|B|H]]|D|@]|E|$]]|$1|O|3|-4|5|6|7|24|8|@]|D|@]|E|$]]|$1|P|3|-4|5|6|7|25|8|@]|D|@]|E|$]]|$1|Q|3|R|5|6|7|26|8|@$9|27|A|28|B|C]]|D|@]|E|$]]|$1|S|3|-4|5|6|7|29|8|@]|D|@]|E|$]]|$1|T|3|U|5|N|7|2A|8|@]|D|@]|E|$]]|$1|V|3|-4|5|6|7|2B|8|@]|D|@]|E|$]]|$1|W|3|-4|5|6|7|2C|8|@]|D|@]|E|$]]|$1|X|3|Y|5|6|7|2D|8|@$9|2E|A|2F|B|H]|$9|2G|A|2H|B|H]|$9|2I|A|2J|B|C]]|D|@]|E|$]]|$1|Z|3|10|5|6|7|2K|8|@$9|2L|A|2M|B|C]]|D|@]|E|$]]|$1|11|3|-4|5|6|7|2N|8|@]|D|@]|E|$]]|$1|12|3|13|5|6|7|2O|8|@]|D|@]|E|$]]|$1|14|3|-4|5|6|7|2P|8|@]|D|@]|E|$]]|$1|15|3|16|5|N|7|2Q|8|@$9|2R|A|2S|B|H]]|D|@]|E|$]]|$1|17|3|-4|5|6|7|2T|8|@]|D|@]|E|$]]|$1|18|3|19|5|6|7|2U|8|@$9|2V|A|2W|B|H]]|D|@]|E|$]]|$1|1A|3|1B|5|6|7|2X|8|@]|D|@]|E|$]]|$1|1C|3|-4|5|6|7|2Y|8|@]|D|@]|E|$]]|$1|1D|3|1E|5|6|7|2Z|8|@]|D|@$9|30|A|31|1|32]]|E|$]]|$1|1F|3|-4|5|6|7|33|8|@]|D|@]|E|$]]]|1G|$1H|$5|1I|1J|1K|E|$1L|1M]]]]

C's <code>size_t</code> and C++'s <code>std::size_t</code> are both same. 

In C, it's defined in <code>&lt;stddef.h&gt;</code> and in C++, its defined in <code>&lt;cstddef&gt;</code> whose contents are the same as C header (see the quotation below). Its defined as unsigned integer type of the result of the sizeof operator.

C Standard says in §17.7/2,

<blockquote>
 size_t which is the unsigned integer type of the result of the sizeof operator
</blockquote>

And C++ Standard says (about <code>cstddef</code> header) in §18.1/3,

<blockquote>
 The contents are the same as the Standard C library header , with the following changes.
</blockquote>

So yeah, both are same; the only difference is that C++ defines <code>size_t</code> in <code>std</code> namespace. 

Please also notice that the above line also says "with the following changes" which isn't referring to <code>size_t</code>. Its rather referring to the new additions (mostly) made by C++ into the language (not present in C) which are also defined in the same header.

<hr>

Wikipedia has very good info about range and storage size of size_t:

<blockquote>
 Range and storage size of size_t
 
 The actual type of size_t is
 platform-dependent; a common mistake
 is to assume size_t is the same as
 unsigned int, which can lead to
 programming errors,[3][4] when moving
 from 32 to 64-bit architecture, for
 example.
 
 According to the 1999 ISO C
 standard (C99), size_t is an unsigned
 integer type of at least 16 bits.
</blockquote>

And the rest you can read from <a href="http://en.wikipedia.org/wiki/Size_t" rel="noreferrer">this page</a> at wikipedia.

blocks|key|2606358|text|std::size_t实际上是stddef.h的size_t。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2606359|cstddef提供了以下内容：|2606360|#include+<stddef.h>
namespace+std+
{
++using+::ptrdiff_t;
++using+::size_t;
}|code-block|syntax|javascript|2606361|...effectively将先前的定义带入std名称空间。|2606362|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

std::size_t is in fact stddef.h's size_t.

cstddef gives the following:

<pre><code>#include &lt;stddef.h&gt;
namespace std 
{
 using ::ptrdiff_t;
 using ::size_t;
}
</code></pre>

...effectively bringing the previous definition into the std namespace.

blocks|key|346197|text|来自C%2B%2B03+"17.4.3.1.4+Types"：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|346198|346199|对于标准C库中的每个类型T(脚注169)，类型::T和std::T保留给实现，并且在定义时，::T应与std::T相同。|blockquote|346200|346201|346202|和脚注169：|346203|346204|这些类型包括clock_t、div_t、FILE、fpos_t、lconv、ldiv_t、mbstate_t、ptrdiff_t、sig_atomic_t、size_t、time_t、tm、va_list、wctrans_t、wctype_t和wint_t。|346205|346206|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|R|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]|$1|G|3|-4|5|6|7|T|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|U|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|E|7|W|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|X|8|@]|9|@]|A|$]]|$1|N|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|O|$]]

From C++03 "17.4.3.1.4 Types":

<blockquote>
 For each type T from the Standard C library (footnote 169), the types ::T and std::T are reserved to the implementation and, when defined, ::T shall be identical to std::T.
</blockquote>

And footnote 169: 

<blockquote>
 These types are clock_t, div_t, FILE, fpos_t, lconv, ldiv_t, mbstate_t, ptrdiff_t, sig_atomic_t, size_t, time_t, tm, va_list, wctrans_t, wctype_t, and wint_t.
</blockquote>

What are the differences between <code>size_t</code> and <code>std::size_t</code> in terms of where they are declared, when they should be used and any other differentiating features?

Difference between size_t and std::size_t

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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size_t和std::size_t在声明的位置、应该使用的时间以及其他区别功能方面有什么不同？

问size_t与std::size_t的区别
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