一个字节加空指针？由两个？ [英] Increment void pointer by one byte? by two?

问题描述

我有一个叫空指针 PTR 。我想通过字节数来增加该值。有没有办法做到这一点？

I have a void pointer called ptr. I want to increment this value by a number of bytes. Is there a way to do this?

请注意，我想这样做在避免产生更多的变​​数。

Please note that I want to do this in-place without creating any more variables.

我可以做类似 PTR =（无效*）（+（（字符*）PTR））;

推荐答案

您不能在空指针，因为指针运算都是在大小所指向的对象。

You cannot perform arithmetic on a void pointer because pointer arithmetic is defined in terms of the size of the pointed-to object.

您可以，但是，转换指针到的char * ，做那个指针运算，然后将其转换回一个无效* ：

You can, however, cast the pointer to a char*, do arithmetic on that pointer, and then convert it back to a void*:

void* p = /* get a pointer somehow */;

// In C++:
p = static_cast<char*>(p) + 1;

// In C:
p = (char*)p + 1;

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