Program crashes while trying to do a check in constructor

[tbscope]

I don't know what you mean by name of the pointer. The filename, or the object name?

file = 0 because there's a problem opening the file:

RETURN VALUES
Upon successful completion fopen(), fdopen(), and freopen() return a FILE
pointer. Otherwise, NULL is returned and the global variable errno is
set to indicate the error.

Use errno to see which error occured.
http://www.manpagez.com/man/3/fopen/

And print out the exect file path that you're trying to open, maybe there's something wrong with it.

[SixDegrees]

It isn't just pointers. When a routine can fail, you need to check status upon return before proceeding. In this case, you're trying to open a file - an operation that is not guaranteed to succeed. The filename may be wrong; permissions may not allow you to open the file; the disk the file is on my not be mounted; just to name a few of the possible failure modes.

[hakermania]

In a very strange way the program now works fine. i can't understand why but errno returned Success and the Preferences dialog opened normally. Anyway, thx for the help!