How to get the size of dynamically (using malloc or calloc )allocated memory?

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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?

Malloc -> how much memory has been allocated?

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

It's implementation specific at this point. For example when you're in the Linux kernel you can get this information for memory allocated with kmalloc: `stuff = kmalloc(1,GFP_KERNEL); printk("I got: %zu bytes of memory\n", ksize(stuff));` Obviously that only works within the Linux kernel, you'd need to get an answer tied to the malloc implementation you're using. — Mike, Oct 09 '12 at 16:09

score 4 · Answer 1 · answered Oct 09 '12 at 15:36

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.

answered Oct 09 '12 at 15:36

alk

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score 2 · Answer 2 · answered Oct 09 '12 at 15:37

2

No. Not without using extra data somewhere that stores the allocated sizes.

answered Oct 09 '12 at 15:37

HonkyTonk

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Thanks... Yup you are right we can use structure to track the size.... – Dixit Singla Oct 09 '12 at 16:08

How to get the size of dynamically (using malloc or calloc )allocated memory?

2 Answers2

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