Re: Bus error using lua_touserdata

[Costas Calamvokis <cc28@...>]

Please ignore my last message, for some reason gdb was not telling
me the correct location of the crash. Once I had the correct location
it was clear I had messed the stack up.
Many apologies!

> I have a problem: when I call lua_touserdata() on a file pointer
> in the io table I get a bus error.
>
> I'm doing this because I need to go through all variables and do 
> something for any I find that are of a particular userdata type (using 
> C++).
>
> I have this working pretty much, I start at _G, recurse through 
> everything and when I find userdata I do this:
>
>      if ( lua_type(L,-1) == LUA_TUSERDATA ) {
>         int *ud =(int *) luaL_checkudata_noerror(L, -1, utype);
>         if (ud != NULL) {
>
> Where luaL_checkudata_noerror is just a copy of luaL_checkudata from
> the auxlib with the bit that generates a error if the type is wrong
> commented out, the start looks like:
>
> LUALIB_API void *luaL_checkudata_noerror (lua_State *L, int ud, const 
> char *tname) {
>   void *p = lua_touserdata(L, ud);
>
> ^that's the line that gives the bus error, when it is called with
> one of the file pointers.
>
> I think it may have something to do with the environment of the 
> userdata? But I'm not sure how to fix it.
>
> Alternatively, if there was a way to avoid recursing into the library 
> stuff without having a list of things to skip (which is my current 
> workaround), that would be nice too.
>
> thanks,
> Costas