[ILUG] Re: thoughts on malloc...

[John P. Looney]

On Wed, Mar 27, 2002 at 12:13:02AM +0000, kevin lyda mentioned:
> now for free to work, malloc has to do accounting.  so each call
> requires malloc to record each location returned and the size of each.
> so somewhere there's a table that says 20(10), 30(5), 35(5), 40(10),
> 50(10).  it might be an actual table or it might be just before the
> block allocated or whatever.
 
 I may be wrong, but I don't think there is just a table, as such. when
you do;

    malloc(50);

 and it returns something like 0x23288322, it has actually put its
accounting info 32 bytes back, in 0x23288302. So, when you
free(0x23288322), it steps back 32 bytes, checks how much etc. and where,
and then marks the mini-allocation free, in the table.

 As unix people, we should really know exactly how this works. Anyone care
to explain ?

Kate

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