Re: Does malloc() have to zero the block?

[Ralph Hempel <rhempel@...>]

Roberto Ierusalimschy wrote:
> > It turns out that realloc() is the only library function that is
> > called, and my implementation of realloc() calls malloc() if the
> > pointer to the original data is NULL.
>
> First you should check whether the new size is not zero. (malloc(0) does
> allocate memory on some systems...)

Does Lua ever realloc() or malloc() 0 bytes?

As Lua sends all memory requests through realloc(ptr,size) with the
assumption that a NULL ptr means allocate me a new block...

What are the expected semantics of:

1. realloc() an existing block to a size of 0 bytes?
2. realloc() a new block to a size of 0 bytes?

I have instrumented my code to see what the typical size range of
malloc()/realloc()/free() requests is and I see lots of requests in
the 32 to 128 byte size. I don't see any requests in the 0 bytes size.

I'm wondering if my heap is getting horribly fragmented because
my realloc() tends to "break off" the higher memory and put it
in the free list if a block is being downsized.

I think that I may try to do something like limit the block sizes
to some minimal value, and possibly try to find a new block EVERY
time a block is actually reallocated to avoid fragmenting the small
memory blocks.

Ralph