NULL Pointer Returned by fopen - but no Errors

I'm attempting to use fopen to open a file. I'm using an absolute path, the file does exist, and it's not corrupt. Also, all system users have full access to read/write the file.

const char* filename = "absolute\\path\\to\\file.something";
const char* mode = "rb";

FILE* file = fopen(filename, mode);

std::cout << "Errors: " << strerror(errno) << std::endl;
std::cout << "File errors: " << ferror(file) << std::endl;
perror(filename);

fclose(file);

All the error reporting shows no errors at all, yet fopen returns a null pointer. If I try to seek the file I get an `Access Violation 0x00000014, which, from what I've read, just means the pointer is null. :)

Error reports:

• strerror(errno): "No error"
• ferror(file): 0
• perror(filename): "No error"

What other error checking could I possibly do? What's the next thing to try in order to figure this out?

To explain why I'm mixing C with C++: I'm going to be using a C library which needs a FILE handle, otherwise I would've used fstream. So, the hope is to get this fopen working so I can pass the FILE over to the C library. The rest of my project is in C++. :)

UPDATE #1:

This check does not work for me:

if (file == NULL) {
    std::cout << "File is null" << std::endl;
}

This check does work for me:

if (file->_ptr == NULL) {
    std::cout << "_ptr is null" << std::endl;
}

UPDATE #2:

This shows the FILE as not NULL:

std::cout << static_cast<void*>(file) << std::endl;

This shows the FILE's pointer as 00000000 (NULL):

std::cout << static_cast<void*>(file->_ptr) << std::endl;

UPDATE #3:

@chux has enlightened me. The file does indeed open correctly, as I just did a quick check and printed to the console the contents of the file and it didn't fail at all.

I was misinterpreting the file->_ptr as showing NULL to be the "true" value of the pointer. However, even though stepping through the code in the debugger shows it as NULL, I was able to print the contents of the file - it was opened successfully all along!

Perhaps this question should be started again - perhaps elsewhere - due to the fact I now realise this is not an fopen issue, but that of the library I'm passing the FILE to. The library is experiencing the exception that originally brought my attention to checking if the file opened correctly, and eventually to seeing (in debugging) that the _ptr shows as NULL - which was misleading to me.

How embarrassing. :)

You need to save errno before invoking any functions that may change it:

FILE* file = fopen(filename, mode);
int error_code = errno;
std::cout << "Errors: " << strerror(error_code) << std::endl;

In this particular code std::cout << "Errors: " may change errno.