How free () knows how much free memory?

Question

Possible duplicate:
C-programming: how to find out how much for free?

In this fragment

void main() {
void *p = malloc(300);
printf("%d",sizeof(*p));
free(p);
}

How to freely know a lot of memory, is it supposed to be released from the void pointer?

I believe that if there is an internal table / function, it should be available to find out the sizes of any objects, while the output printfis1

Answer 1

malloc and free do their own hidden accounting so that they can do the right thing.

, sizeof() , , sizeof() , malloc/free .

Answer 2

. comp.lang.c · 7.26

Answer 3

. , , , .. sizeof(void), .

Answer 4

malloc , . free malloc , , .

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