Critical error detected c0000374 - C++ dll returns pointer off allocated memory to C#

I have a c++ dll which serving some functionality to my main c# application. Here i try to read a file, load it to memory and then return some information such as the Pointer to loaded data and count of memory blocks to c#. The Dll reads file to memory successfully but on the return to the main application, program crashes due to Heap Corruption(Critical error detected c0000374).

The code is quite simple and straightforward and I have done some similar things before with no problem, However i could not figure out what makes the problem here, I tried to allocate memory using "new, malloc and GlobalAlloc" but neither did help. Codes are as follow:

C++ MyDll:

typedef unsigned long         U32;

extern "C" __declspec(dllexport) int ReadFile(LPSTR Path, U32** DataPtr, U32* Count)
   FILE *fp;
   U32 *Data;
   CString tempStr(Path);
   long fSize;

   if(!(fp = fopen(tempStr, "rb"))) {
    return 0;

   // Obtain File Size;
   fseek(fp, 0, SEEK_END);
   fSize =  ftell(fp);

   Data = (U32 *)GlobalAlloc(0, fSize);
   if(Data == NULL) {
            return -1;

    // Copy file into the buffer.
        if(!(*Count = fread(Data, sizeof(U32), fSize / sizeof(U32), fp))) {
           return -2;

   *DataPtr = (U32 *)Data;
       return 1;

C# Application:

        [DllImport(@"MyDll.dll", CallingConvention= CallingConvention.Cdecl)]
    private static extern int ReadFile([MarshalAs(UnmanagedType.LPStr)]string Path, out IntPtr dataPtr, out uint Count);

private void readDump(string Path)
    uint count = 0;
    IntPtr Data = new IntPtr();

       if(ReadFile(Path, out Data, out count) == 1) //The Program crashes just right after this statement
           //Do Something ...
    catch() {}


The program crashes on both debug and release mode. Unless I pause the program in debug mode after loading the file and call some blocks of memory in the "Visual Studio's Immediate window". The size of files to be loaded are around 64MB and we have more than 2GB unused ram on the PC.

UPDATE: I noticed that, some third party programs which they working before, crash with "Exception Code: c0000005", and some other weird things happens in Windows 7 (the Host). so I tested the code in another installation of windows and everything seems to work as they should. So probably it's related be the Windows 7. Now how could I fix the problem? "sfc /scannow" failed to find any issue.


If all your code is indeed what is shown above, then I don't see the problem. However, when I get this issue, sometimes its because malloc/new/whatever detects heap corruption, often this corruption has already occurred previously in the program, but the crash has been delayed until the next call to new/malloc.

If you read other files, or allocate or free other buffers before the above is executed and crashes, I would look there for problems. Perhaps throw a bunch of asserts anywhere you write to buffers and check the bounds and what you are writing for overruns. Sorry this isn't a concrete answer, I do not have enough rep to leave this advice as a comment.

You are allocating the output data 2 times. Once in C# as new IntPtr and then in C++ as GlobalAlloc and then return the Pointer Returned by GlobalAlloc. So the Pointer returned by new intPtr has been lost.

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