将void指针强制转换为char指针指针是否安全

Question

Just wondering if it's safe to cast like this:

char **cpp;
// ... allocation and what not 
void *vp = (void *)cpp;
// ...
cpp = (char **)vp;

should a void ** be used or is void * fine? This works on a couple of my boxes without issue but was wondering if it could cause problems on certain systems.

Answer 1

The cast is always safe, dereferencing it is safe as long as the pointer is valid. The only case where you'd use a void ** is when you plan to dereference it to get a void * .

However, unless you do pointer arithmetics it won't really matter. As you can see on http://codepad.org/UcZUA0UL it works fine no matter if you use void* or void ** . Before you actually use the pointer you are going to cast it back to char ** anyway - so it is never dereferenced while it's void -ish.

Answer 2

The casting (and usage afterwards) from void* , if the original pointer was char ** .

You shouldn't use void** .