Add `LL.setdtor()` function to add a "destructor" to any Lua object.

`setdtor('description', object, function)` returns a proxy userdata object
referencing object and function. When the proxy is garbage-collected, or at
the end of the script, its destructor calls `function(object)`.

The original object may be retrieved as `proxy._target`, e.g. to pass it to
the `table` library. The proxy also has a metatable with metamethods
supporting arithmetic operations, string concatenation, length and table
indexing. For other operations, retrieve `proxy._target`. (But don't assign to
`proxy._target`. It will appear to work, in that subsequent references to
`proxy._target` will retrieve the replacement object -- however, the
destructor will still call `function(original object)`.)

Fix bugs in `lua_setfieldv()`, `lua_rawgetfield()` and `lua_rawsetfield()`.

Add C++ functions `lua_destroyuserdata()` to explicitly destroy a
`lua_emplace<T>()` userdata object, plus `lua_destroybounduserdata()`. The
latter can bind such a userdata object as an upvalue to pass to `LL.atexit()`.

Make `LL.help()` and `LL.leaphelp()` help text include the `LL.` prefix.

1 files changed, 62 insertions, 0 deletions

diff --git a/indra/newview/scripts/lua/test_setdtor.lua b/indra/newview/scripts/lua/test_setdtor.lua
new file mode 100644
index 0000000000..743c5168d0
--- /dev/null
+++ b/indra/newview/scripts/lua/test_setdtor.lua
@@ -0,0 +1,62 @@
+inspect = require 'inspect'
+
+print('initial setdtor')
+bye = LL.setdtor('initial setdtor', 'Goodbye world!', print)
+
+print('arithmetic')
+n = LL.setdtor('arithmetic', 11, print)
+print("n =", n)
+print("n._target =", n._target)
+print("getmetatable(n) =", inspect(getmetatable(n)))
+print("-n =", -n)
+for i = 10, 12 do
+    -- Comparison metamethods are only called if both operands have the same
+    -- metamethod.
+    tempi = LL.setdtor('tempi', i, function(n) print('temp', i) end)
+    print(`n <  {i}`, n <  tempi)
+    print(`n <= {i}`, n <= tempi)
+    print(`n == {i}`, n == tempi)
+    print(`n ~= {i}`, n ~= tempi)
+    print(`n >= {i}`, n >= tempi)
+    print(`n >  {i}`, n >  tempi)
+end
+for i = 2, 3 do
+    print(`n + {i} =`, n + i)
+    print(`{i} + n =`, i + n)
+    print(`n - {i} =`, n - i)
+    print(`{i} - n =`, i - n)
+    print(`n * {i} =`, n * i)
+    print(`{i} * n =`, i * n)
+    print(`n / {i} =`, n / i)
+    print(`{i} / n =`, i / n)
+    print(`n % {i} =`, n % i)
+    print(`{i} % n =`, i % n)
+    print(`n ^ {i} =`, n ^ i)
+    print(`{i} ^ n =`, i ^ n)
+end
+
+print('string')
+s = LL.setdtor('string', 'hello', print)
+print('s =', s)
+print('#s =', #s)
+print('s .. " world" =', s .. " world")
+print('"world " .. s =', "world " .. s)
+
+print('table')
+t = LL.setdtor('table', {'[1]', '[2]', abc='.abc', def='.def'},
+               function(t) print(inspect(t)) end)
+print('t =', inspect(t))
+print('t._target =', inspect(t._target))
+print('#t =', #t)
+print('t[2] =', t[2])
+print('t.def =', t.def)
+t[1] = 'new [1]'
+print('t[1] =', t[1])
+
+print('function')
+f = LL.setdtor('function', function(a, b) return (a .. b) end, print)
+print('f =', f)
+print('f._target =', f._target)
+print('f("Hello", " world") =', f("Hello", " world"))
+
+print('cleanup')