[RFA]: Remove unused header files.

[Andrew Cagney]

"J.T. Conklin" wrote:

> In several instances it identified two header files, <errno.h> and
> <linespec.h>, as unnecessary because <errno.h> is unconditionally
> included in defs.h; and the only declaration in linespec.h
> (decode_line_1) is also defined in symtab.h.
> 
> I'm unsure about the correct way to handle those are.  As long as
> errno.h is included in defs.h, I see no reason to include it in any
> *.c file.  One could argue that errno.h should be remove from defs.h,
> but since errno (or the E* macros) is used in almost every file, I
> suspect we'd have to #include it in many files.

I'm aware of two strategies:

	o	Every module include a
		single header file and
		that suck in all the other
		header files.

		Makes for very simple but
		absolutely lethal make file
		dependencies :-)

	o	Every module define their
		own header and each component
		pull in the header files it
		is using.

		A variation on this theme has
		each of these header files
		[not] sucking in anything they
		refer to.

GDB clearly has a foot in both of those camps (and the second foot has
both of those variations squished between its toes .... :-).

"defs.h" contains declarations that various modules can't live without. 
Each module header contains declarations specific to their module.  How
self contained a module header file is,  is pretty arbitrary.

To get back to your question.  I expect the status quo to largely
remain:

	o	defs.h provide declarations for
		the things that all of GDB uses.

	o	module headers try to be largely
		self contained.  If they refer
		to other headers then suck
		those headers in.

So <errno.h> should be included but (to give a counter example)
<endian.h> should be given the boot (see TODO file for details).

	Andrew