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6.9

Access violation when code is moved to another method

Asked by MikeDotNet555 in C++ Programming Language, C Programming Language

I have a c++ code that loads a library dynamically and then make function calls into it using function pointers.

It all works fine if I call the library Init() function and the GenerateKeys() function in the same methdo it works fine, otherwise I get the following exception:
Unhandled exception at 0x025b2168 in WardenCPP.exe: 0xC0000005: Access violation reading location 0xcccccce4. and it seem to break along the lines of >      WardenCPP.exe!mainCRTStartup()  Line 399

I will put a examples in code (trimmed down functions).
Code 1 is working fine, but Code 2 is not. All I try to do is move the code in another method to allow it to be called at a later time. As you can see in the code, it is the exact same thing but splitted into 2 methods instead of 1. I had the exact same problem when I tryied to do this in c# but I tough that c# was moving function pointers but now I guess it is another problem that is not related to c# GC (since this is cpp it should leave stuff where they were created, no?).




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typedef's:
typedef void (__thiscall *fnGenerateRC4Keys)(_WardenFuncList** ppFncList, void* lpData, DWORD dwSize);
typedef WardenFuncList** (__fastcall *fnInitializeModule)(DWORD* lpPtr2Table); 

Code 1:
WardenHandler::InitializeWarden(const unsigned char *pModule)
{
    //some processing...
    ppWFuncList = fpInitializeModule((DWORD*)&tableptr);
    void* ptr = (void*)*ppWFuncList;
	WardenFuncList* pWardenFuncList = (WardenFuncList*)ptr; 
    fpGenerateRC4Keys = pWardenFuncList->fpGenerateRC4Keys;
	
	uint32_t dwGameHash = 0xaef0e532;
	uint32_t *pGameGash = &dwGameHash;
	
	fpGenerateRC4Keys(ppWFuncList, pGameGash, 4);
} 
Code 2
WardenHandler::InitializeWarden(const unsigned char *pModule)
{
    ppWFuncList = fpInitializeModule((DWORD*)&tableptr);
    return ppWFuncList;
}
unsigned char* WardenHandler::GenerateRC4KeysEx(_WardenFuncList** ppWFuncList, void* seed, int len)
{
	fnGenerateRC4Keys fpGenerateRC4Keys; 
	void* ptr = (void*)*ppWFuncList;
	WardenFuncList* pWardenFuncList = (WardenFuncList*)ptr; 
    fpGenerateRC4Keys = pWardenFuncList->fpGenerateRC4Keys;
	
	uint32_t dwGameHash = 0xaef0e532;
	uint32_t *pGameGash = &dwGameHash;
	
        //Crash on the following line.
	fpGenerateRC4Keys(ppWFuncList, pGameGash, 4); 
	return 0;
}
 
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[+][-]11/02/09 11:03 AM, ID: 25722483Accepted Solution

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Zones: C++ Programming Language, C Programming Language
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Solution Provided By: jkr
Participating Experts: 1
Solution Grade: B
 
[+][-]11/02/09 10:04 AM, ID: 25721803Expert Comment

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[+][-]11/02/09 10:44 AM, ID: 25722265Expert Comment

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[+][-]11/02/09 10:48 AM, ID: 25722328Author Comment

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