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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Crash in MemoryLoadLibraryEx(): 0xC0000005: Access violation reading location 0x00000000.","articleBody":"I'm using the latest version of MemoryModule (f02a8e6a382d42b2fcc43e93729ebdef3ce420eb).\n\nTo reproduce, replace `SampleDLL.cpp` with:\n\n``` cpp\nclass Callable\n{\npublic:\n    virtual int call() { return 0; }\n};\n\nCallable * GetCallable()\n{\n    static Callable callable;\n    return \u0026callable;\n}\n\nint i = GetCallable()-\u003ecall();\n```\n\n(this should be valid C++ code as far as I'm aware)\n\nand `DllLoader.cpp` with:\n\n``` cpp\n#define WIN32_LEAN_AND_MEAN\n\n#include \u003cwindows.h\u003e\n#include \u003ctchar.h\u003e\n#include \u003cstdio.h\u003e\n#include \u003cmalloc.h\u003e\n\n#include \"../../MemoryModule.h\"\n\n#define DLL_FILE TEXT(\"..\\\\SampleDLL\\\\SampleDLL.dll\")\n\nvoid LoadFromFile(void)\n{\n    HINSTANCE handle = LoadLibrary(DLL_FILE);\n    if (handle == NULL)\n        return;\n\n    FreeLibrary(handle);\n}\n\nvoid LoadFromMemory(void)\n{\n    FILE *fp;\n    unsigned char *data=NULL;\n    size_t size;\n    HMEMORYMODULE handle;\n\n    fp = _tfopen(DLL_FILE, _T(\"rb\"));\n    if (fp == NULL)\n    {\n        _tprintf(_T(\"Can't open DLL file \\\"%s\\\".\"), DLL_FILE);\n        goto exit;\n    }\n\n    fseek(fp, 0, SEEK_END);\n    size = ftell(fp);\n    data = (unsigned char *)malloc(size);\n    fseek(fp, 0, SEEK_SET);\n    fread(data, 1, size, fp);\n    fclose(fp);\n\n    handle = MemoryLoadLibrary(data);\n    if (handle == NULL)\n    {\n        _tprintf(_T(\"Can't load library from memory.\\n\"));\n        goto exit;\n    }\n\n    MemoryFreeLibrary(handle);\n\nexit:\n    if (data)\n        free(data);\n}\n\nint main(int argc, char* argv[])\n{\n    //LoadFromFile();\n    LoadFromMemory();\n    return 0;\n}\n```\n\nIf `LoadFromFile()` is run, the program exits with 0.\n\nHowever, if `LoadFromMemory()` is run, it crashes with:\n\n```\nException thrown at 0x0008146E in DllLoader.exe: 0xC0000005: Access violation reading location 0x00000000.\n```\n\nStacktrace:\n\n```\n    0008146e()  Unknown\n    [Frames below may be incorrect and/or missing]  \n    ucrtbased.dll!__initterm\u001E() Unknown\n    00082d41()  Unknown\n    00082be9()  Unknown\n    00082fbd()  Unknown\n    000831df()  Unknown\n\u003e   DllLoader.exe!MemoryLoadLibraryEx(const void * data, void * (const char *, void *) * loadLibrary, int (...) * (void *, const char *, void *) * getProcAddress, void (void *, void *) * freeLibrary, void * userdata) Line 560   C\n    DllLoader.exe!MemoryLoadLibrary(const void * data) Line 433 C\n    DllLoader.exe!LoadFromMemory() Line 42  C++\n    DllLoader.exe!main(int argc, char * * argv) Line 60 C++\n    DllLoader.exe!invoke_main() Line 74 C++\n    DllLoader.exe!__scrt_common_main_seh() Line 264 C++\n    DllLoader.exe!__scrt_common_main() Line 309 C++\n    DllLoader.exe!mainCRTStartup() Line 17  C++\n    kernel32.dll!@BaseThreadInitThunk@12\u001E() Unknown\n    ntdll.dll!___RtlUserThreadStart@8\u001E()    Unknown\n    ntdll.dll!__RtlUserThreadStart@8\u001E() Unknown\n```\n\nLine 560 in `MemoryModule.c`:\n\n``` cpp\n// notify library about attaching to process\nBOOL successfull = (*DllEntry)((HINSTANCE)code, DLL_PROCESS_ATTACH, 0);\n```\n\nStrangely enough, if _both_ `LoadFromLibrary()` and `LoadFromMemory()` are run (and in that order!), there is no crash.\n","author":{"url":"https://github.com/Gama11","@type":"Person","name":"Gama11"},"datePublished":"2015-11-27T15:19:40.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":14},"url":"https://github.com/31/MemoryModule/issues/31"}