从void **转换为char **有多危险 [英] How dangerous is conversion from void ** to char **

问题描述

因此，我们知道标准不会强制指针大小相等. (此处和此处)(而非谈论函数指针)

So we know that the standard doesn't force pointer sizes to be equal. (here and here) (and not talking about function pointers)

我想知道实际上这可能是个问题.我们知道void *可以容纳任何内容，因此如果指针大小不同，那将是最大大小.鉴于此，将void **分配给char **意味着麻烦.

I was wondering how in reality that can be an issue. We know that void * can hold anything, so if the pointer sizes are different, that would be the biggest size. Given that, assigning a void ** to a char ** means trouble.

我的问题是，假设void *和char *具有相同的大小将有多危险?真的有一个不正确的架构吗?

My question is how dangerous would it be to assume void * and char * have the same size? Is there actually an architecture where this is not true?

此外，我不希望听到16位dos信息！ ;)

Also, 16-bit dos is not what I want to hear! ;)

推荐答案

void *和char *保证具有相同的大小.

void * and char * are guaranteed to have the same size.

void **不能保证具有与char **相同的大小(但是在实现上非常有可能).

void ** is not guaranteed to have the same size as char ** (but very likey on your implementation they will).

(C99，6.2.5p27)指向void的指针应与指向字符类型的指针具有相同的表示和对齐要求.指向其他类型的指针不必具有相同的表示或对齐要求.

(C99, 6.2.5p27) "A pointer to void shall have the same representation and alignment requirements as a pointer to a character type [...] Pointers to other types need not have the same representation or alignment requirements."

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