Re: luaL_register crashed on iOS

[曹煦 <cao.xu@...>]

Sorry for the misleading conclusion.

The truth is that the broken code still crash under 5.1.5. However，it happened to work fine after  I inserted some lua_checkstack()  calls before  those luaL_register(), which only work fine with lua5.1.5 (the code still crash under 5.1.4). So I simply thought it’s caused by the lua version.

Thanks for the explanation.


> 在 2015年9月17日，下午9:46，Roberto Ierusalimschy <roberto@inf.puc-rio.br> 写道：
> 
>> It seems like a bug of luaV_settable of version 5.1.4, and works fine under 5.1.5
> 
> As lhf said, your code is broken; you should fix it even if it works
> under 5.1.5.
> 
> The documentation of 'luaL_register' [1] is clear:
> 
>  When called with a non-null libname, luaL_register creates a new table t,
>  [...]
>  In any case the function leaves the table on the top of the stack.
> 
> So, you push one new element on the stack at each call to
> 'luaL_register'. The documentation also says [2]:
> 
>  When you interact with Lua API, you are responsible for ensuring
>  consistency. In particular, you are responsible for controlling
>  stack overflow. [...]
> 
>  Whenever Lua calls C, it ensures that at least LUA_MINSTACK stack
>  positions are available. LUA_MINSTACK is defined as 20, [...]
> 
> As you call 'luaL_register' more than 20 times without popping the
> results, you have a stack overflow. Anything that happens after that
> is undefined behavior (which means it can even work as expected).
> 
> If your corrected code still crashes under 5.1.4, please tell us.
> 
> 
> [1] http://www.lua.org/manual/5.1/manual.html#luaL_register
> [2] http://www.lua.org/manual/5.1/manual.html#3.2
> 
> -- Roberto
>