Re: Strong tables in Lua 5.4

[Roberto Ierusalimschy <roberto@...>]

> Every `t[k] = f()` of every module and dependency (and their
> dependencies recursively) would have to be checked for memory leaks.
> And this won't be the typical Lua 5.x to Lua 5.(x+1) situation where
> you try out a dependency on a new Lua version and it doesn't) build
> because lua_dump now has an extra argument, or lua_objlen was renamed
> to lua_rawlen in a Lua/C module, or you get a crash with a stack trace
> in your testsuite because setfenv() doesn't exist anymore.

I still think you are exaggerating the problem, but I may be wrong. I
would like to know how many real programs have the construction
t[k] = f() where f() returning 'nil' is not a bug. (You mentioned
that table.move could create that kind of thing. I asked for a real
scenario, but got no answer.)

More concretely, I propose a little experiment: suppose that Lua raises
a run-time error for every assignment of nils to tables except in
explicit assignments with a constant nil (t[k]=nil). How frequently this
error will occurr without hinting a hidden bug in the code? (Please,
any answer should be about some piece of real, useful code where that
could happen.)

-- Roberto