hide-ifdef-expand-reinclusion-protection

hide-ifdef-expand-reinclusion-protection is a variable defined in `hideif.el'.
Its value is

t

Documentation:
Non-nil means don't hide an entire header file enclosed by #ifndef...#endif.
Most C/C++ headers are usually wrapped with ifdefs to prevent re-inclusion:

----- beginning of file -----
#ifndef _XXX_HEADER_FILE_INCLUDED_
#define _XXX_HEADER_FILE_INCLUDED_
xxx
xxx
xxx...
#endif
----- end of file -----

The first time we visit such a file, _XXX_HEADER_FILE_INCLUDED_ is
undefined, and so nothing is hidden. The next time we visit it, everything will
be hidden.

This behavior is generally undesirable. If this option is non-nil, the outermost
#if is always visible.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 25.1 of Emacs.