Re: lua_checkstack and luaL_checkstack

[David Jones <drj@...>]

On 11 Sep 2008, at 10:32, Aladdin Lampé wrote:

> Thank you Patrick.
>
> If I understand correctly, this means that I should first have a  
> call to luaL_checkstack() each time I use one of the following  
> functions:
> - lua_pushboolean
> - lua_pushcclosure
> - lua_pushcfunction
> - lua_pushfstring
> - lua_pushinteger
> - lua_pushlightuserdata
> - lua_pushliteral
> - lua_pushlstring
> - lua_pushnil
> - lua_pushnumber
> - lua_pushstring
> - lua_pushthread
> - lua_pushvalue
> - lua_pushvfstring
>
> Is there any way of telling the Lua interpreter once-for-all to  
> grow the stack "when needed", "if possible" and "with a specified  
> message in case of error" instead of a segmentation fault?

No, but it's rarely needed.  Whenever Lua calls C it ensures that  
there are at least 20 (or LUA_MINSTACK) slots available on the Lua  
stack for your C code to use.  Therefore if your C code doesn't push  
more than 20 items, you'll be fine.  If your C code does push more  
than 20 items, but you can get some bound on the number, then you can  
check once at the beginning of the C function that you have enough  
space on the stack.

You only need to repeatedly call checkstack if you have a C function  
that uses an amount of Lua stack that grows without bound (for  
example, a loop that pushes lots of strings onto the stack, the  
concatenates them in one go at the end of the loop).  Such cases are  
rare, and there are usually better ways of doing it.

Cheers,
 drj