Possible Duplicate:
determine size of dynamically allocated memory in c
newbie questions about malloc and sizeof
How can I get the size of an array from a pointer in C?
int **arrofptr;
arrofptr = (int **)malloc(sizeof(int *) * 2);
arrofptr[0] = (int *)malloc(sizeof(int)*6144);
arrofptr[1] = (int *)malloc(sizeof(int)*4800);
Now i have to know that how many bytes are allocated in arrofptr,arrofptr[0],arrofptr[1]? is there any way to know the size?
if we will print
sizeof(arrofptr);
sizeof(arrofptr[0]);
sizeof(arrofptr[1]);
then it will print 4
No, there is no way to find how much memory a pointer is referring to.
At least not on any system, so no portable way.
No. Not without using extra data somewhere that stores the allocated sizes.
来源：https://stackoverflow.com/questions/12803562/how-to-get-the-size-of-dynamically-using-malloc-or-calloc-allocated-memory