upgrading to 4.0(a)
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- Subject: upgrading to 4.0(a)
- From: Stephan Herrmann <stephan@...>
- Date: 2000年8月30日 17:02:03 +0200 (MEST)
Hi,
Finally, I made it to upgrade to Lua4.0(alpha).
Here are my (unpleasant) findings, some of which concern the
list of incompatibilities, but there is also one severe bug.
* 'gc' tagmethod not settable from Lua
* somewhere I learned, that type() returns two values: type and tag.
Although it was undocumented, it is a feature that disappeared.
And its disappearance produces errors that are not at all obvious.
* lua_seterrormethod disappeared. (Why?)
* lua_State argument needed also in non-reentrant programs for luaL_verror()
* how about a little guide on adapting custom made main-programs?
(creating the lua_State, using begin/endblock() for opening libs..)
* below is a program that screws up the internal Lua-Stack. Doesn't look
really dangerous, does it?
Changing the if-condition to 1 changes the bug to a
segmentation violation. Using replacement (2) works around the bug.
(Don't ask me, how I found that =:-0 )
Sorry, if some of this has been reported on the list before. I couldn't
follow the busy discussion of the last weeks very thoroughly.
(maybe Lua4.0beta will change everything, but I had the time for
upgrading now, not in October :-(
ciao
Stephan
PS: I also had to dig into the sources a little deeper, because I need
a version of foreach which has repeatable order also for string indices.
Something comparable to foreachi, but -- for strings. Easiest way seems
to be to use qsort before iterating. Unfortunately using memcpy and qsort
to do the job requires low-level access to internal data structures..
I had posted a suggestion of "sortedforeach" some time ago and I still
wonder, whether I'm the only one who needs this predictable ordering?
BTW: what is a tag, that is guaranteed to be invalid? -2 ?
----------------------------------------------------------------------
$debug
function func1 () end
function func2()
local a
if nil then
-- (1) if 1 then
print("T1")
a={func1()}
-- (2) a={}; a[1]=func1()
end
print("T2") -- print is no longer print..
end
func2()
--------------------------------------------------------------------------
Stephan Herrmann
----------------
Technical University Berlin
Software Engineering Research Group
http://swt.cs.tu-berlin.de/~stephan
phone: ++49 30 314 73174
--------------------------------------------------------------------------