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Re: Fkill_emacs NO_RETURN

From: Dan Nicolaescu
Subject: Re: Fkill_emacs NO_RETURN
Date: Sun, 09 Apr 2006 12:13:36 -0700

Eli Zaretskii <address@hidden> writes:

  > This change:
  >     2006-04-09  Dan Nicolaescu  <address@hidden>
  >         * puresize.h (pure_write_error): Mark as NO_RETURN.
  >         * lisp.h (args_out_of_range, args_out_of_range_3)
  >         (Fkill_emacs): Likewise.
  > marks Fkill_emacs as __attribute__((no_return)) for those versions of
  > GCC which support that.  I think this change is for the worse: now GCC
  > whines that a function that is marked no-return returns a value.  This
  > is because Fkill_emacs has this at its end:
  >       exit (INTEGERP (arg) ? XINT (arg) : EXIT_SUCCESS);
  >       /* NOTREACHED */
  >       return Qnil;
  > The ``NOTREACHED return'' is there because DEFUN declares a function
  > that returns a Lisp_Object, and some compilers will complain if
  > there's no return statement in such a function.
  > So either we find a clean way to condition `return Qnil' on NO_RETURN
  > being defined to nothing, or we should revert this change.  

How about just deleting the return statement?
gcc has supported the noreturn attribute since at least gcc-2.95. 
Other compilers might just warn if they don't realize that "exit" does
not return. I think quite a few modern compilers know that.

  > (Why was it made, anyway?)

One of the Coverity reports was due to the fact that the tool did not
realize that Fkill_emacs cannot return. 

IMO marking the function as not returning will prevent having to
analyze similar errors in the future with other checking tools.

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