5.1 request: reporting external memory usage to Lua (Re: Fix needed in 5.0.2 Makefile)

[Jay Carlson <nop@...>]

Luiz Henrique de Figueiredo wrote:

> We'll look into this (and other Makefile issues) carefully for Lua 5.1.

Another thing for 5.1:

The C implementation of iostring uses an external buffer, with a pointer 
stored in a userdata.  The userdata itself is quite small.   I would 
like to tell the garbage collector that it can recover (say) 5 megabytes 
if it claims a particular 5 megabyte iostring instance.  Without this, 
common code patterns may result in a tiny Lua heap that doesn't know 
enough to free the monster external buffers.  (I am also adding a manual 
 f:reset() method to allow users to clean them up by hand, but that's 
gross.)

My first thought was to add to the API a way of code adding or 
subtracting from the global "amount of memory allocated" number that Lua 
holds.  If C code added to it, it would be responsible for subtracting 
it at gc time.

If I could realloc a userdata, that would work for this case too.

Jay