Re: Re[2]: _CrtIsValidHeapPointer Problem

["jason zhang" <jzhang@...>]

Thank you. 
So what should I do? Dynamic link to the core lua lib?



----- Original Message ----- 
From: "cloudwu" <cloudwu@163.com>
To: "Lua list" <lua@bazar2.conectiva.com.br>
Sent: Wednesday, September 13, 2006 5:55 PM
Subject: Re[2]: _CrtIsValidHeapPointer Problem


> Hello jason,
> 
> Friday, August 25, 2006, 6:03:32 PM, you wrote:
> 
> jz> Thanks all of you.
> jz> I suspend this problem for about one week and look at it again today.
> jz> I compared the DLL case and exe case. The same C code works well
> jz> in a exe but cause a heap error in dll. Below is what I get during debuging:
> 
> jz> When create a array in a DLL, it will allocate some memory and they are
> jz> stored in the stack of the interpreter. When the script finished, the interpreter
> jz> will call lua_close(L) to release the resources. But I found that, it unload the
> jz> dll before clear the stack, so, the memory allocated in the DLL is invalid.
> 
> jz> For Lua 5.1
> 
> jz> lstate.c, line 210, in the function LUA_API void lua_close (lua_State *L)
> jz> do {  /* repeat until no more errors */
> jz>     L->ci = L->base_ci;
> jz>     L->base = L->top = L->ci->base;
> jz>     L->nCcalls = 0;
> jz>   } while (luaD_rawrunprotected(L, callallgcTM, NULL) != 0); // Line 210
> jz> Inside the luaD_rawrunprotected function, it will call
> jz> luaC_callGCTM() function to clear all the user data,
> jz> Finally, the routine go to the static int gctm (lua_State *L) function in loadlib.c, which
> jz> unload the dll from the interpreter. So , all the memory allocated in DLL is invalid.
> 
> jz> Is my analysis correct?
> 
> jz> What I can't understand is, why only the array cause the
> jz> problem, while normal table works.
> jz> And I also don't understand why it works if I insert an element with index zero.
> 
> jz> Please help me.
> 
> jz> Thank you so much.
> 
> I guess you linked luacore twice. The lua interpreter static link
> luacore lib once, and your dll link it again.
> 
> In ltable.c , line 73 :
> 
> -------------------------------------------
> #define dummynode               (&dummynode_)
> 
> static const Node dummynode_ = {
>  {{NULL}, LUA_TNIL},  /* value */
>  {{{NULL}, LUA_TNIL, NULL}}  /* key */
> };
> -------------------------------------------
> 
> The dummynode is the static stuct .
> 
> When you create a table, it may call
> ------------
>  if (size == 0) {  /* no elements to hash part? */
>    t->node = cast(Node *, dummynode);  /* use common `dummynode' */
>    lsize = 0;
>  }
> ------------
> 
> And when the table release, it checks t->node
> -----------
> void luaH_free (lua_State *L, Table *t) {
>  if (t->node != dummynode)
>    luaM_freearray(L, t->node, sizenode(t), Node);
>  luaM_freearray(L, t->array, t->sizearray, TValue);
>  luaM_free(L, t);
> }
> -----------
> 
> If you linked luacore twice, there are 2 copy of dummynode existed. It
> may cause your problem.
> 
> ps. Lua table will put the index zero to hash part not array part.
> 
> -- 
> Best regards,
> cloudwu                            mailto:cloudwu@163.com
>            http://www.codingnow.com
> 
> [人生是不公平的]
> 
> 
>