Re: Function call with number parameter becomes a string parameterinside the function

[Asko Kauppi <askok@...>]

Not having read the whole thread, but... I have snippet of code that  
seems like what everyone's after. Or.. is it? :)


const char* _glua_tolstring_safe( lua_State* L, int argn, uint* /*  
size_t* */ len_ref )
{
const char* ptr;

	// To bypass the int->str conversion side-effect, we make a local
	// copy of the stack entry, get a pointer to it, and remove it.
	// Even though the item is removed from stack, our pointer remains
	// valid until Lua does Garbage Collection (which is only after
	// GLUA_FUNC_END so this is safe :).

	_glua_pushvalue( L, argn );		// Makes [-1] a local copy
		{
		ptr= _glua_tolstring_raw(L,-1,len_ref);	  // may change the local copy
		}
	_glua_remove( L, -1 );			// Removes the copy from stack

	return ptr;		// Should remain valid until GLUA_FUNC_END.
}


Now... I hear you cry, it's not safe.  This is another thread we've  
been up to a while back, namely whether Lua C API functions can cause  
garbage collection to be ignited, while a C function is running... I  
wish they did not :) ; that way the push-remove-butstilluse trick  
would be valid.  It _is_ handy, and btw it does work in practise (at  
least, seems so...)

Perhaps I need to mark my code, that the commented behaviour actually  
is not guaranteed.   **sigh**  ;)
-asko


Daniel Collins kirjoitti 30.6.2006 kello 4.42:

> Nobody has suggested what seems to me an obvious variation.  
> lua_tostring
> leaves the original value unchanged, and pushes either nil or the  
> string
> onto the top of the stack. That way you can copy the string if  
> desired,
> then pop it when you are finished with it.
>
> - DC