Re: Bug in debug.sethook

["Wesley Smith" <wesley.hoke@...>]

Is memfault the name of memory leak detection software?  I can't seem
to find anything about it.  Any links?

thanks,
wes

On 8/16/07, Rici Lake <lua@ricilake.net> wrote:
> (Reported by sanooj in #lua)
>
> Summary: the debug library's hook function can call lua_rawget() on nil,
> causing unpredictable behaviour (probably a segfault).
>
> The rawget is at line 212 in ldblib.c; it assumes that the lookup of
> KEY_HOOK in the registry will return a table. The table is created by
> gethooktable() which is called by db_sethook (debug.sethook). Under
> normal circumstances, this means that the table will be present when
> the hook function is invoked.
>
> Unfortunately, it is possible for the lua_createtable() in gethooktable()
> to fail and throw a memory error. Since db_sethook calls lua_sethook()
> before calling before gethooktable(), this could result in the hook
> function being installed without a valid hooktable, leading to the
> call of rawget() on nil when the return hook subsequently fires.
>
> Of course, this is highly unlikely. It was apparently discovered by
> use of the memfault tool.
>
> It is only fair to quote a bit of the conversation on #lua:
>
> sanooj: spent a lot of time yesterday hammering lua with memfault
> rici: did you find one?
> sanooj: just one
> sanooj: the rest of the time.. wow..I've *never* seen software as stable
> as this.
>
>
>
>
>