来自 友好的***一个>:

stdlib.h 和 stddef.h 头文件定义了一种名为 size_t 的数据类型，用于表示对象的大小.接受大小的库函数期望它们的类型为 size_t，而 sizeof 运算符的计算结果为 size_t.

The stdlib.h and stddef.h header files define a datatype called size_t which is used to represent the size of an object. Library functions that take sizes expect them to be of type size_t, and the sizeof operator evaluates to size_t.

size_t 的实际类型是平台相关的；一个常见的错误是假设 size_t 与 unsigned int 相同，这可能会导致编程错误，尤其是在 64 位架构变得更加普遍的情况下.

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, particularly as 64-bit architectures become more prevalent.

另外，查看 为什么 size_t 很重要一个>