[Ada] Crash on improper pragma Weak_External

This patch adds a guard on the use of pragma Weak_External. This pragma
affects link-time addresses of entities, and does not apply to types.
Previous to this patch the compiler would abort on a misuse of the
pragma.

2019-07-01  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* sem_prag.adb (Analyze_Pragma, case Weak_External): Pragma only
	applies to entities with run-time addresses, not to types.

gcc/testsuite/

	* gnat.dg/weak3.adb, gnat.dg/weak3.ads: New testcase.

From-SVN: r272876

gcc/ada/ChangeLog

+2019-07-01  Ed Schonberg  <schonberg@adacore.com>
+
+	* sem_prag.adb (Analyze_Pragma, case Weak_External): Pragma only
+	applies to entities with run-time addresses, not to types.
+
 2019-07-01  Piotr Trojanek  <trojanek@adacore.com>
 
 	* einfo.adb, sem_ch7.adb, sem_prag.adb, sem_util.adb: Update

gcc/ada/sem_prag.adb

@@ -25608,6 +25608,12 @@ package body Sem_Prag is
                Ent := Underlying_Type (Ent);
             end if;
 
+            --  The pragma applies to entities with addresses.
+
+            if Is_Type (Ent) then
+               Error_Pragma ("pragma applies to objects and subprograms");
+            end if;
+
             --  The only processing required is to link this item on to the
             --  list of rep items for the given entity. This is accomplished
             --  by the call to Rep_Item_Too_Late (when no error is detected

gcc/testsuite/ChangeLog

 2019-07-01  Ed Schonberg  <schonberg@adacore.com>
 
+	* gnat.dg/weak3.adb, gnat.dg/weak3.ads: New testcase.
+
+2019-07-01  Ed Schonberg  <schonberg@adacore.com>
+
 	* gnat.dg/prot7.adb, gnat.dg/prot7.ads: New testcase.
 
 2019-07-01  Richard Biener  <rguenther@suse.de>

gcc/testsuite/gnat.dg/weak3.adb

+--  { dg-do compile }
+
+package body Weak3 is
+
+   type T is new Integer;
+   pragma Weak_External (T); --  { dg-error "pragma applies to objects and subprograms" }
+   X : T;
+
+   procedure Foo is null;
+
+end Weak3;

gcc/testsuite/gnat.dg/weak3.ads

+package Weak3 is
+   procedure Foo;
+end Weak3;