re PR c++/92695 (P1064R0 - virtual constexpr fails if object taken from array)

	PR c++/92695
	* decl2.c (mark_used): Don't call note_vague_linkage_fn for pure
	virtual functions, even if they are declared inline.

	* g++.dg/warn/inline3.C: New test.

From-SVN: r278802

gcc/cp/ChangeLog

+2019-11-28  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/92695
+	* decl2.c (mark_used): Don't call note_vague_linkage_fn for pure
+	virtual functions, even if they are declared inline.
+
 2019-11-16  Jason Merrill  <jason@redhat.com>
 
 	Implement P1814R0, CTAD for alias templates.

gcc/cp/decl2.c

@@ -5596,8 +5596,11 @@ mark_used (tree decl, tsubst_flags_t complain)
 	vec_safe_push (no_linkage_decls, decl);
     }
 
-  if (TREE_CODE (decl) == FUNCTION_DECL && DECL_DECLARED_INLINE_P (decl)
-      && !DECL_INITIAL (decl) && !DECL_ARTIFICIAL (decl))
+  if (TREE_CODE (decl) == FUNCTION_DECL
+      && DECL_DECLARED_INLINE_P (decl)
+      && !DECL_INITIAL (decl)
+      && !DECL_ARTIFICIAL (decl)
+      && !DECL_PURE_VIRTUAL_P (decl))
     /* Remember it, so we can check it was defined.  */
     note_vague_linkage_fn (decl);
 

gcc/testsuite/ChangeLog

+2019-11-28  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/92695
+	* g++.dg/warn/inline3.C: New test.
+
 2019-11-27  Jakub Jelinek  <jakub@redhat.com>
 
 	PR rtl-optimization/92510

gcc/testsuite/g++.dg/warn/inline3.C

+struct S {
+  inline virtual void foo () = 0;	// { dg-bogus "used but never defined" }
+#if __cplusplus > 201703L
+  constexpr virtual void bar () = 0;	// { dg-bogus "used but never defined" "" { target c++2a } }
+#else
+  inline virtual void bar () = 0;	// { dg-bogus "used but never defined" "" { target c++17_down }  }
+#endif
+  S () {}
+};
+struct T : public S {
+  inline virtual void foo () {}
+#if __cplusplus > 201703L
+  constexpr virtual void bar () {}
+#else
+  inline virtual void bar () {}
+#endif
+  T () {}
+};
+T t;
+void foo (S *s) { s->foo (); s->bar (); }