Re: The life cycle of userdata values?

[Marc Balmer <marc@...>]

So.. 

> Am 25.07.2016 um 17:04 schrieb Marc Balmer <marc@msys.ch>:
> 
> I am hunting a ghost.  This is my ghost:
> 
> Previously, we used the following construct in C code:
> 
> p = malloc(sizeof int)
> *p = 42
> 
> /* Do a Lua API call that might error (longjmp) out */
> 
> free(p)
> 

This leaks memory, if the API call errors out.

> p = lua_newuserdate(L, sizeof int)
> *p = 42
> 
> /* Do a Lua API call that might error (longjmp) out */

This has the risk of the memory being invalidated by the
garbage collector.

> p = lua_newuserdate(L, sizeof int)
> l = luaL_ref(L, -1)
> *p = 42
> 
> /* Do a Lua API call that might error (longjmp) out */
> 
> luaL_unref(l)

This would leak memory as well if the API call errors out,
because the userdata is still referenced.