bin/71613: [PATCH] traceroute(8): cleanup of the usr.sbin/traceroute6 code

[Dan Lukes]

	OK

	There seems to be several ways to correct the problem.

	We can avoid the warning by adding "const" or "volatile" or __used or 
by removing "static".

	The "remove static" way can't be used - non-static symbol is global 
variable - so const char copyright[] from one source will collide with 
the same name variable from another source. It's not problem only when 
there are one source file only or we can guarantee unique variable name.

	It seems we need 'static'. Unfortunately, static unused variable can be 
optimized out.

	Adding 'const' and/or __used clear the warning, but doesn't prevent 
"optimized-out" problem. The 'const' shall be used because the string is 
constant. We can use __used, but it has limited portability.

	We still have the problem the variable may be optimized out.

	The 'volatile' is way to tell an ANSI C compiler "this variable may be 
modified via mechanism you don't know about it" - it mean "count it as 
used" and "don't optimize it". Note, the 'const' and 'static' are ANSI C 
keywords also, so compiler knowing 'static' shall handle 'volatile' as well.

	Conclusion (for the case we can't guarantee the unique name of variable):
static   MUST
const    SHALL
__used   SHALL
volatile MUST

So my recomentation is:
0: static volatile const char __used copyright[]=...

because of __unused the sys/cdefs.h must be included first.

The other way to fix it is
1: the sys/copyright.h way - e.g. plain char variable - but the variable 
must be unique across the sources which sound not so easy for me


2. the __COPYRIGHT way, but
2a: IDSTRING must be corrected first
2b: the '\n' must be removed from the source.

sys/cdefs.h must be included first.

	In my opinion the preference shall be 2a then 0 then 1 or 2b but it's 
not strict. The commiter shall select the best way.


					Dan