Persistent access error calling a function returned by GetProcAddress
Here is my code. It seems straighforward to do, but somehow it just isn't working. The final call to the function always fails with an access error.
extern "C"
{
typedef const char* (*Init_fptr_t)();
HMODULE CMolNet::LoadDLL()
{
string dir = "C:\\MyDllDir\\";
CA2W dirw( dir.c_str() );
SetDllDirectory(dirw);
string dllfile = CombinePath(dir.c_str(), "mydll.dll");
CA2W dllfilew( dllfile.c_str() );
mDLL = LoadLibraryEx(dllfilew,0,LOAD_WITH_ALTERED_SEARCH_PATH);
DWORD err = GetLastError();
Init_fptr_t iFunc = (Init_fptr_t)GetProcAddress(mDLL,"Init");
const char *res = (*iFunc)();
}
}
mydll.dll is a third party dll. I do not have the source code, but the prototype of the function in the header is as follows:
extern "C" {
const char* Init();
}
mydll.dll itself depends on several other dlls, stored in directory "C:\MyDllDir", hence the call to SetDllDirectory.
Some observations:
- I could not get vanilla LoadLibrary to work, but
LoadLibraryEx
with the arguments should seemed to work (in thatGetLastError
returns0
) - The address of the dll returned seems odd (
0x43900000
) - T开发者_C百科he address of the function returned by
GetProcAddress
is also odd (0x43902b34
), but reassuringly DLL Export Viewer reports the Init function as having an offset of0x00002b34
) - Calling the returned function always throws an access errors. I have tried every combination of
_ccdecl
,__stdcall
etc on thetypedef
for the function but always get the same error. I have tried with and withoutextern C
Other data:
- This piece of c++ code is being called from a managed environment
- I am running on windows 7, 64 bit, but compiling the unmanaged part as win32
What am I doing wrong? How can I debug this? I have tried dependency walker and dll export viewer and everything seems ok.
Everything is fine. You just don't need to use *
when you're calling function through a pointer. Call it like ordinary function:
const char *res = iFunc();
instead of
const char *res = (*iFunc)();
精彩评论