[Rd] How to unload R.dll successfully by FreeLibrary

暮如雪 snowyfox at 163.com
Thu Feb 5 09:09:08 CET 2015

    I've some C++ code which try to load R.dll and execute some R command, then unload R.dll, yet it seems fail to unload it, so second time to call the function hangs since it is trying to Initialize R again(this is not allowed as documented). Anyone can tell me why, thanks.
//the following is my c++ code, used in a Visual Studio 2012 Console Application
#define ORAPI__cdecl
typedefBOOL(ORAPI*PFN_Rf_initEmbeddedR)(int argc, char *argv[]);
typedefvoid(ORAPI*PFN_Rf_endEmbeddedR)(int fatal);

#define STR_R_DLL_PATH_T("D:\\R\\R-3.1.2\\bin\\i386\\R.dll")
HMODULEm_hRDll = LoadLibrary(STR_R_DLL_PATH);
if ( m_hRDll )
PFN_Rf_initEmbeddedR pfnInit = (PFN_Rf_initEmbeddedR)GetProcAddress(m_hRDll, "Rf_initEmbeddedR");
PFN_Rf_endEmbeddedR pfnEnd = (PFN_Rf_endEmbeddedR)GetProcAddress(m_hRDll, "Rf_endEmbeddedR");

char*szArgs[] = {"REmbeddedPostgres", "--gui=none", "--silent"};
BOOL bRet = pfnInit(_countof(szArgs), szArgs); //call second time, this function will not return
//do something.
FreeLibrary(m_hRDll); //==> After this, R.dll still in memory, as I can see in Visual Studio 2012, Module window
//testing code end
int _tmain(int argc, _TCHAR* argv[])
_simple_test(); //first time, seems fine.
_simple_test(); //second time, hangs...
return 0;

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