egcs, RFC: patch for possible -Wmissing-noreturn warning

[Jeffrey A Law]

  In message < 199810111726.NAA19753@caip.rutgers.edu >you write:
  > 	The problem is that I'm getting a small number of false
  > positives when `static inline void' functions are used.
I wonder if we actually perform enough analysis on static inlines to determine
can_reach_end in c-decl.c (which in turn determines
current_function_returns_null.

  > I'm also
  > getting some hits when exit() is called from main().  Although
  > technically correct (its thus a function which doesn't `return',) I
  > think its one case which should not be flagged. 

[ ... ]
  > 
  > Also if I have:
  > 
  >  > main()
  >  > {
  >  >   return 0;
  >  > }
  > 
  > all's well.
  > 
  > 
  > 	However, if I have:
  > 
  >  > main()
  >  > {
  >  >   exit(0);
  >  > }
  > 
  > 	I get:
  > 
  >  > foo.c: In function `main':
  >  > foo.c:4: warning: function does not return, and is not declared `noreturn'
  > 
  > Again, this is technically correct.  But should we offer a pass from
  > `main', or do we encourage people to use the `return', not `exit' style?
Not sure.  I hate making special exceptions like this, but given that we've
already made several for "main" I guess another isn't so bad.

jeff