Corrupted Stack...

Hello...
As soon as this function returns the Debug Window in VisualC++ reports this error:

"Run-Time Check Failure #2 - Stack around the variable 'fBuffer' was corrupted."

Code:

---

int cFile::GetType(LPCWSTR filename)
{
        HANDLE hFile = NULL;
        char fBuffer[3];
        DWORD nread = 0;

        hFile = CreateFile(filename, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
        if (hFile == NULL)
                return -1;

        ZeroMemory(fBuffer, sizeof(char) * 4);
        ::ReadFile(hFile, fBuffer, 4, &nread, NULL);
        if (nread < 4)
                return -1;

        if (fBuffer[0] == 82 && fBuffer[1] == 73 && fBuffer[2] == 70 && fBuffer[3] == 70)
                return FILE_TYPE_AUDIO;

        if (fBuffer[0] == 77 && fBuffer[1] == 84 && fBuffer[1] == 104 && fBuffer[1] == 100)
                return FILE_TYPE_MIDI;

        return 0;
}

---

Why??

Because you're calling ZeroMemory() on a buffer of only 3 chars and telling it to zero out 4.

BTW, this is the C section, and that's C++ code. ;)

ReadFile also uses 4 bytes buffer
You should close the file in this function ( you do not return handle for future use)

your use of "magic" numbers is also not too good

yes...you're right

I've tried declaring fBuffer[4] instead of fBuffer[3] and everything works fine...
Anyway shouldn't fBuffer[3] be 4 bytes long (of type char)?

Thanks

char array[SIZE]
has exactly SIZE bytes... what you ask is what you get.

Valid indexes are from 0 to SIZE-1

Ooops!

I was thinking that an array had indexes from 0 to size...Well thanks a lot!