[win32] can _open() return valid negative fd ?

Question

Is it possible that win32's _open() return valid FD that is negative ?

In other words, is comparison

 if( (fd=_open(...)) < 0) error...;

as safe as form

 if( (fd=_open(...)) == -1) error...;

?

I am asking because all msdn examples
are in form if(fd == -1 ), and never form if( fd < 0).

Answer 1

No. Negative values are all errors. In fact, if you look at read(), it asserts the fd is between 0 and 31.

Answer 2

Windows file descriptors are borrowed from MS-DOS 2.0 file handles, which were loosely based on Unix file descriptors, all of which are indices into the process's table of file control blocks. So a valid file handle must be non-negative.