GetLocalizedText sometimes crashing Wow

[peterwurst]

Heya guys,

I hooked the 3D3 EndScene function in Wow to call some functions like lua Dostring and GetText.

Sometimes (not often once out of 1000-5000 calls) my Wow seems to crash:

ERROR #132 (0x85100084) Fatal Exception
Exception:	0xC0000005 (ACCESS_VIOLATION) at 001B:005A82F7

The instruction at "0x005A82F7" referenced memory at "0x00000008".
The memory could not be "read".

I looked at the offset in IDA and it seems to be the GetLocalizedText function I'm calling to get lua DoString results.


As said before, it's not crashing frequently but in unregular timespans.

.text:005A82F0 sub_5A82F0      proc near  
.text:005A82F0                                        
.text:005A82F0
.text:005A82F0 arg_0           = dword ptr  8
.text:005A82F0 arg_4           = dword ptr  0Ch
.text:005A82F0
.text:005A82F0                 push    ebp
.text:005A82F1                 mov     ebp, esp
.text:005A82F3                 push    ebx
.text:005A82F4                 push    esi
.text:005A82F5                 mov     esi, ecx
.text:005A82F7                 mov     eax, [esi+8]
.text:005A82FA                 mov     ebx, [eax+4]
.text:005A82FD                 push    edi
.text:005A82FE                 mov     edi, [eax]
.text:005A8300                 call    sub_7BC8D0
.text:005A8305                 cmp     edi, eax
.text:005A8307                 jnz     short loc_5A8319
.text:005A8309                 cmp     ebx, edx
.text:005A830B                 jnz     short loc_5A8319
.text:005A830D                 mov     eax, [esi+0FD0h]
.text:005A8313                 movzx   eax, byte ptr [eax+1Ch]
.text:005A8317                 jmp     short loc_5A8323

What could cause the crash?

[schlumpf]

You may want to pass "this".

[peterwurst]

I'm already calling it with this

typedef const char* (__thiscall * luaGetText)(void* pPlayer, const char* luaVar, DWORD_PTR unknown);

Otherwise the function would crash as soon I am calling it, but it seems like random crashes.

[Cypher]

It's obviously because you're passing in 0 as pPlayer for those calls. You need to check the pointer is valid before you start using it and throwing it around.

Come on people, this is basic stuff.

If you have to ask about this stuff you really need to get back to the books.

[rootguy]

your this pointer seems to be 0