Re: bug in 5.0

[Chromix <Chromix@...>]

> As far as we checked, this bug is not present in Lua 5.1 beta.

I've created another variant of my demonstration script for 5.1,
which uses 5 empty tables that occupy about 60MB of RAM.
If it is not a bug, it is at least unexpected behaviour.

I've used http://www.lua.org/work/lua-5.1-beta.tar.gz
for testing the script on linux.


-------<snip>-------
-- Weak values & garbage collection problem, Version for Lua 5.1 beta

--[=[
    Output on linux:
    Lua 5.1 (beta)
    Loop    1
    44603   -->     12602
    Loop    2
    57185   -->     25185
    Loop    3
    69768   -->     37768
    Loop    4
    82351   -->     50351
    Loop    5
    94934   -->     62934
]=]


print( _VERSION );

local t = {};
for loop = 1, 5 do
    print( "Loop", loop );

    -- Create a new local table with weak values.
    local tTest = setmetatable( {}, { __mode = "v" } );

    -- Fill the table, and make sure the GC won't get triggered
    -- while it is being filled.
    collectgarbage( "stop" );
    for i = 1, 1000000 do
        tTest[i] = {};
    end

    -- The table will contain 1000000 entries now.
    local count = 0;
    table.foreach( tTest, function() count = count + 1; end );
    assert( count == 1000000 );

    -- Run the GC. All values are weak and unreferenced...
    local usage = math.floor( collectgarbage("count") );
    collectgarbage();

    -- ...so the table is empty now.
    assert( not next( tTest ) );

    print( usage, "-->", math.floor( collectgarbage("count") ) );

    -- Store the empty table. This should not consume a lot of RAM
    t[loop] = tTest;
end
-------</snip>------