sizeof(char)和sizeof(char *)之间的区别 [英] Difference between sizeof(char) and sizeof(char *)

问题描述

我想知道sizeof(char)和sizeof(char *)之间是否有区别:

I'm wondering if there is a difference between sizeof(char) and sizeof(char *) :

char *s;
s = malloc(sizeof(char*)*len + 1);

char *s;
s = malloc(sizeof(char)*len + 1);

是不是一样?

推荐答案

char是字符，并且sizeof(char)定义为1.(

char is a character and sizeof(char) is defined to be 1. (N1570 6.5.3.4 The sizeof and _Alignof operators, paragraph 4)

char*是指向字符的指针，而sizeof(char*)取决于环境.在32位环境中通常为4，而在64位环境中通常为8.

char* is a pointer to a character and sizeof(char*) depends on the environment. It is typically 4 in 32-bit environment and 8 in 64-bit environment.

在sizeof(char*) > sizeof(char)的典型环境中，如果len足够小而不会引起整数溢出，则malloc(sizeof(char*)*len + 1)将(至少尝试)分配比malloc(sizeof(char)*len + 1)更多的内存.

In typical environment where sizeof(char*) > sizeof(char), malloc(sizeof(char*)*len + 1) will (at least try to) allocate more memory than malloc(sizeof(char)*len + 1) if len is small enough not to cause integer overflow.

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