sem_prag.adb (No_Return): Give an error if the pragma applies to a body.

sem_prag.adb (No_Return): Give an error if the pragma applies to a body.

2017-04-25  Bob Duff  <duff@adacore.com>

	* sem_prag.adb (No_Return): Give an error if the pragma applies
	to a body. Specialize the error for the specless body case,
	as is done for (e.g.) pragma Convention.
	* debug.adb: Add switch -gnatd.J to disable the above legality
	checks. This is mainly for use in our test suite, to avoid
	rewriting a lot of illegal (but working) code.	It might also
	be useful to customers. Under this switch, if a pragma No_Return
	applies to a body, and the procedure raises an exception (as it
	should), the pragma has no effect. If the procedure does return,
	execution is erroneous.

2017-04-25  Bob Duff  <duff@adacore.com>

	* exp_ch6.adb (Expand_Actuals): This is the
	root of the problem. It took N as an 'in out' parameter, and in
	some cases, rewrote N, but then set N to Original_Node(N). So
	the node returned in N had no Parent. The caller continued
	processing of this orphaned node. In some cases that caused a
	crash (e.g. Remove_Side_Effects climbs up Parents in a loop,
	and trips over the Empty Parent). The solution is to make N an
	'in' parameter.  Instead of rewriting it, return the list of
	post-call actions, so the caller can do the rewriting later,
	after N has been fully processed.
	(Expand_Call_Helper): Move most of Expand_Call here. It has
	too many premature 'return' statements, and we want to do the
	rewriting on return.
	(Insert_Post_Call_Actions): New procedure to insert the post-call
	actions in the appropriate place. In the problematic case,
	that involves rewriting N as an Expression_With_Actions.
	(Expand_Call): Call the new procedures Expand_Call_Helper and
	Insert_Post_Call_Actions.

From-SVN: r247178