Re: lua5.1: Lua stack is too small for a script that takes over 2048 arguments

[Asko Kauppi <askok@...>]

Would the userdata approach allow bygone string arguments to be GC'ed?

If it does, it would have a slight benefit towards the current make- 
table-up-front approach. Then again, if strings could be pushed in C  
saying "this memory will always be there", there wouldn't be much  
difference again.

In other words, could Lua have a 'lua_pushstring()' that does not  
make a copy of the string contents but uses the ones in ROM/argv that  
the code author says won't ever vanish. I believe that would be  
welcome in 5.2?

LUA_API void  (lua_pushlstring_fixed) (lua_State *L, const char *s,  
size_t l);

and

#define lua_pushliteral(L, s)	\
	lua_pushlstring_fixed(L, "" s, (sizeof(s)/sizeof(char))-1)

-asko


Gé Weijers kirjoitti 20.12.2007 kello 8:27:

> This is a bit of a problem.
>
> Alternatively the arguments could be passed in as a single  
> argument, i.e. an array, or a userdata object pretending to be a  
> read-only array (implementing the length and index operations). The  
> userdata object would not require the allocation of a potentially  
> massive array to store a copy of the argument vector, but would  
> copy the contents of 'argv' to the lua interpreter one string at a  
> time.
>
> The worst case argument vector would be about ARG/MAX zero-byte  
> strings, which would require LUAI_MAXCSTACK to be equal to ARG_MAX,  
> i.e. insanely large.
>
> Gé
>
> On Dec 19, 2007, at 4:03 PM, Norman Ramsey wrote:
>
> > Package: lua5.1
> > Version: 5.1.2-4
> > Severity: normal
> >
> > I just got this rather unhappy result:
> >
> > : nr@homedog 10445 ; label-by-hand -udir /home/nr/tmp/tt2 *
> > lua5.1: stack overflow (too many arguments to script)
> >
> >
> > It seems to me that the Lua interpreter should accept as many
> > arguments as the local operating system is willing to provide.  This
> > number is fairly fuzzy (see http://tinyurl.com/nn8yd for a good
> > discussion of the issues), but the current default of 2048 is
> > unreasonably small for a stock Debian system.  ARG_MAX is 131072 on
> > this system, so supposing we assume each argument is an 8.3 pathname
> > with a trailing null, even leaving room for some environment this is
> > space for about ten thousand arguments.  I suggest that when Lua is
> > built for Debian that line 445 of luaconf.h be changed so that
> > LUAI_MAXCSTACK is more in that range.
> >
> >
> > Norman
> >
> >
> > -- System Information:
> > Debian Release: lenny/sid
> >   APT prefers testing
> >   APT policy: (500, 'testing'), (500, 'stable'), (50, 'unstable')
> > Architecture: i386 (i686)
> >
> > Kernel: Linux 2.6.22-3-k7 (SMP w/2 CPU cores)
> > Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968)
> > Shell: /bin/sh linked to /bin/bash
> >
> > Versions of packages lua5.1 depends on:
> > ii  libc6                         2.7-3      GNU C Library: Shared  
> > libraries
> > ii  libreadline5                  5.2-3      GNU readline and  
> > history libraries
> >
> > lua5.1 recommends no packages.
> >
> > -- no debconf information
>
> --
> Gé Weijers
> ge@weijers.org