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

[David Jones <drj@...>]

On 29 Jun 2006, at 11:34, D Burgess wrote:

> Carsten Fuchs wrote:
> [...]
> > lua_tostring() from my code.
> >
> > However, I'm wondering why lua_tostring() behaves in this (somewhat
> > surprising) manner? This makes it different from all the other  
> > lua_to*()
> > functions, and I wonder why this is so??
> I guess that the conversion to a string means that the string has  
> to be
> allocated and stored somewhere. Numbers and booleans presumably
> do not have the allocation issue.

Exactly.  The string returned from lua_tostring is only valid whilst  
there is a corresponding Lua string on the stack.  So lua_tostring  
must put a Lua string somewhere on the stack.  And the current  
implementation overwrites the number with the string.

I'm sure lots of people have been bitten by this behaviour (I know I  
have).  Maybe it would be better if lua_tostring took an additional  
argument which was the stack slot to overwrite with the Lua string.   
Then it would be more clear that lua_tostring was doing something a  
bit different, and if you didn't want to change your number into a  
string you could do that by specifying a different stack slot.  There  
are other variations that come to mind too.

drj