C语言 size_t 的最大大小
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Maximum size of size_t
提问by Sunil Bojanapally
I know in Creturn type of sizeofoperator is size_tbeing unsigned integer type defined in <stdint.h>. Which means max size of it should be 65535as stated in C99standard 7.18.3:
我知道操作符的C返回类型sizeof是size_t在<stdint.h>. 这意味着它的最大大小应该65535如C99标准7.18.3 中所述：
limit of size_t
SIZE_MAX 65535
However in gcc-4.8.2header file stdint.hhas defined its size much greater than 65535contradicting to which is stated in C99standard as below shown,
然而，在gcc-4.8.2头文件stdint.h中定义的大小比标准中65535规定的要大得多C99，如下所示，
/* Limit of `size_t' type. */
# if __WORDSIZE == 64
# define SIZE_MAX (18446744073709551615UL)
# else
# define SIZE_MAX (4294967295U)
# endif
Kindly help me in understanding why there is a difference or reason behind my misinterpretation.
请帮助我理解为什么我的误解背后存在差异或原因。
回答by Keith Thompson
The standard says that SIZE_MAXmust be at least65535.
标准说SIZE_MAX必须至少为65535。
It specifies no upper bound, and gcc's implementation is perfectly valid.
它没有指定上限，gcc 的实现是完全有效的。
Quoting the reference you cited (emphasis added):
引用你引用的参考文献（强调）：
Its implementation-defined value shall be equal to or greaterin magnitude (absolute value) than the corresponding value given below, with the same sign.
其实现定义的值应等于或大于下面给出的相应值的幅度（绝对值），并具有相同的符号。
