PR c++/87554 - ICE with extern template and reference member.

The removed code ended up setting DECL_INITIAL to the INIT_EXPR returned by
split_nonconstant_init, which makes no sense.  This code was added back in
1996, so any rationale is long lost.

	* decl.c (cp_finish_decl): Don't set DECL_INITIAL of external vars.

From-SVN: r270445

gcc/cp/ChangeLog

+2019-04-18  Jason Merrill  <jason@redhat.com>
+
+	PR c++/87554 - ICE with extern template and reference member.
+	* decl.c (cp_finish_decl): Don't set DECL_INITIAL of external vars.
+
 2019-04-17  Jason Merrill  <jason@redhat.com>
 
 	PR c++/90047 - ICE with enable_if alias template.

gcc/cp/decl.c

@@ -7354,8 +7354,7 @@ cp_finish_decl (tree decl, tree init, bool init_const_expr_p,
 	       && ! (DECL_LANG_SPECIFIC (decl)
 		     && DECL_NOT_REALLY_EXTERN (decl)))
 	{
-	  if (init)
-	    DECL_INITIAL (decl) = init;
+	  /* check_initializer will have done any constant initialization.  */
 	}
       /* A variable definition.  */
       else if (DECL_FUNCTION_SCOPE_P (decl) && !TREE_STATIC (decl))

gcc/testsuite/g++.dg/cpp0x/extern_template-5.C

+// PR c++/87554
+// { dg-options "-O" }
+
+template < class a > class b {
+  static void c(a);
+  static a &create() { c(instance); return mya; }
+
+  static a mya;
+
+public:
+  static a d() { create(); return a(); }
+  static a &instance;
+};
+template < class a > a &b< a >::instance = create();
+class e;
+class f {
+public:
+  void operator()(int g) { h(g); }
+  template < class a > void h(a i) { p(j, i); }
+  e *j;
+};
+class e : public f {
+public:
+  e(int);
+};
+struct k {
+  int l;
+};
+template < class m, class a > void p(m, a) { b< k >::d(); }
+extern template class b< k >;
+int n;
+int o;
+void test() {
+  e out(o);
+  out(n);
+}