C - Size of malloc'd?

Author

Size of malloc'd?

bwaichu@yahoo.com

2006-08-29, 6:56 pm

How do I determine the size of a previously malloc'd buffer?

char *buffer;

buffer = calloc(18, sizeof *buffer);

I cannot do a sizeof(buffer) since it would only return the size of the
pointer. I cannot do sizeof *buffer since it would only return the
size of the pointer type. Is there a right way to do this? Do I need
to manage this information in the program?

bert

2006-08-29, 6:56 pm

bwaichu@yahoo.com wrote:
> How do I determine the size of a previously malloc'd buffer?
>
> char *buffer;
>
> buffer = calloc(18, sizeof *buffer);
>
> I cannot do a sizeof(buffer) since it would only return the size of the
> pointer. I cannot do sizeof *buffer since it would only return the
> size of the pointer type. Is there a right way to do this? Do I need
> to manage this information in the program?

This is covered by questions 7.27 and 7.28 in the FAQ list.
Basically, yes, you need to keep track of this for yourself.
--

Eric Sosman

2006-08-29, 6:56 pm

bwaichu@yahoo.com wrote On 08/29/06 14:20,:
> How do I determine the size of a previously malloc'd buffer?
>
> char *buffer;
>
> buffer = calloc(18, sizeof *buffer);
>
> I cannot do a sizeof(buffer) since it would only return the size of the
> pointer. I cannot do sizeof *buffer since it would only return the
> size of the pointer type. Is there a right way to do this? Do I need
> to manage this information in the program?

This is Question 7.27 in the comp.lang.c Frequently
Asked Questions (FAQ) list

http://www.c-faq.com/

--
Eric.Sosman@sun.com

bwaichu@yahoo.com

2006-08-29, 6:56 pm

Eric Sosman wrote:
> bwaichu@yahoo.com wrote On 08/29/06 14:20,:
>
> This is Question 7.27 in the comp.lang.c Frequently
> Asked Questions (FAQ) list
>
> http://www.c-faq.com/

Thanks for the link. The answer is what I expected.

Thanks!

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