re PR lto/89358 (Combining -std=c++14 and -std=c++17 objects gives ODR warnings)

	PR lto/89358
	* g++.dg/lto/pr89358_0.C: New testcase.
	* g++.dg/lto/pr89358_1.C: New testcase.
	* ipa-devirt.c (skip_in_fields_list_p): New.
	(odr_types_equivalent_p): Use it.

From-SVN: r270355

gcc/ChangeLog

+2019-04-14  Jan Hubicka  <hubicka@ucw.cz>
+
+	PR lto/89358
+	* ipa-devirt.c (skip_in_fields_list_p): New.
+	(odr_types_equivalent_p): Use it.
+
 2019-04-13  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/89093

gcc/ipa-devirt.c

@@ -1282,6 +1282,24 @@ warn_types_mismatch (tree t1, tree t2, location_t loc1, location_t loc2)
     inform (loc_t2, "the incompatible type is defined here");
 }
 
+/* Return true if T should be ignored in TYPE_FIELDS for ODR comparsion.  */
+
+static bool
+skip_in_fields_list_p (tree t)
+{
+  if (TREE_CODE (t) != FIELD_DECL)
+    return true;
+  /* C++ FE introduces zero sized fields depending on -std setting, see
+     PR89358.  */
+  if (DECL_SIZE (t)
+      && integer_zerop (DECL_SIZE (t))
+      && DECL_ARTIFICIAL (t)
+      && DECL_IGNORED_P (t)
+      && !DECL_NAME (t))
+    return true;
+  return false;
+}
+
 /* Compare T1 and T2, report ODR violations if WARN is true and set
    WARNED to true if anything is reported.  Return true if types match.
    If true is returned, the types are also compatible in the sense of
@@ -1548,9 +1566,9 @@ odr_types_equivalent_p (tree t1, tree t2, bool warn, bool *warned,
 		 f1 = TREE_CHAIN (f1), f2 = TREE_CHAIN (f2))
 	      {
 		/* Skip non-fields.  */
-		while (f1 && TREE_CODE (f1) != FIELD_DECL)
+		while (f1 && skip_in_fields_list_p (f1))
 		  f1 = TREE_CHAIN (f1);
-		while (f2 && TREE_CODE (f2) != FIELD_DECL)
+		while (f2 && skip_in_fields_list_p (f2))
 		  f2 = TREE_CHAIN (f2);
 		if (!f1 || !f2)
 		  break;

gcc/testsuite/ChangeLog

+2019-04-14  Jan Hubicka  <hubicka@ucw.cz>
+
+	PR lto/89358
+	* g++.dg/lto/pr89358_0.C: New testcase.
+	* g++.dg/lto/pr89358_1.C: New testcase.
+
 2019-04-14  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	PR fortran/85448

gcc/testsuite/g++.dg/lto/pr89358_0.C

+/* { dg-do link } */
+/* { dg-options "-std=c++17"  } */
+#include <map>
+
+extern void test();
+
+int main()
+{
+        std::map<int, int> m;
+        test();
+}

gcc/testsuite/g++.dg/lto/pr89358_1.C

+/* { dg-options "-std=c++14"  } */
+#include <map>
+
+void test()
+{
+        std::map<int, int> m;
+}