Re: [Dev-C++] Re: malloc , extra bytes ! Somewhat urgent !

[Per W. <pw...@ia...>]

Stop bothering about the size of the returned memory block.

The allocation functions are only required to return AT LEAST the required
amount of memory, or a NULL pointer.

Internally, they normally add 8-16 byte of internal header for
book-keeping on the heap, i.e. to allow the heap manager to walk free and
used memory block.

Besides, most heap managers performs one of the following:
- rounds each block up to the nearest 8 or 16 byte increment.
- allocates the nearest larger 2^n size.
- uses the buddy system and allocates the nearest larger block size.

As a result - for allocation of very small objects, it might often
be better to allocate a bunch of objects at a time, and keep pool of
evailable objects in a list.

In the example below, the calloc call MUST use sizeof(BYTE). The
statement calloc(1000,BYTE) doesn't make sense.

/Per W

On Mon, 24 Feb 2003, Danny Roelofs wrote:

> Hi,
>
> Well i dont realy know what youre doing with it.. and i never used calloc but it seems your allocating memory for 1000 bytes
> and a additional 8 bytes..  sizeof(byte) reserves 8 bytes in my opinion. is it perhaps that you have to do this:
>
> calloc(1000,BYTE) instead of calloc(1000,sizeof(BYTE))
>
> Well i actualy dont know.. i am just programming in C for just a month or so..
>
>
>   ----- Original Message -----
>   From: veenurs
>   To: dev...@li... ; ra...@ww...
>   Sent: Monday, February 24, 2003 1:16 AM
>   Subject: [Dev-C++] Re: malloc , extra bytes ! Somewhat urgent !
>
>
>
>
>   Hi !
>   It seems too simple .But what is it !?
>   if( (buffer = ( PBYTE )calloc( 1000 ,sizeof(BYTE) )) == NULL ){
>          ------
>         -------
>   }
>     size = _msize( buffer );
>
>   The size I get it is not 1000 , but 1008  !Same for malloc. Any subsequent call to realloc  does not add  the 8 bytes,though  .
>
>   [ Dev Cpp Version 4.9.7.0 ]
>   What's happening ?
>   BTW - "Generate debugging info" is OFF .
>   Thanks in advance .
>
>   -Rahul.
>
>
>